Gross and Microscopic Anatomy of the Structures

GROSS AND MICROSCOPIC ANATOMY OF THE STRUCTURES

INVOLVED IN THE PRODUCTION OF SEMINAL

FLUID IN THE CHICKEN

Carl Edward Knight

A THESIS

Submitted to Michigan State University in partial fulfillment of the requirements for the degree of

MASTER OF SCIENCE

Department of Poultry Science

1967

5//

ABSTRACT

GROSS AND MICROSCOPIC ANATOMY OF THE STRUCTURES INVOLVED IN THE PRODUCTION OF SEMINAL FLUID IN THE CHICKEN

by Carl Edward Knight

The gross and microscopic anatomy of the structures involved in

the production of seminal fluid in the chicken are discussed. The

phallus, round bodies, lymph folds and vascular bodies were found to

be the structures directly involved in seminal fluid production. Sur-

rounding structures were discussed for orientation and illustrations

were presented to complement the discussion.

The-cloaca is composed of three chambers; proctodeum, urodeum,

and coprodeum. Externally it appears as two lips, a larger dorsal lip

and a smaller ventral lip. Its surface is covered with epithelium

characteristic of the general body surface.

The proctodeal fold arises from the margin of the lips and forms

the cloacal opening by its incomplete central fusion.

The proctodeal cavity is the most caudal of the cloacal chambers.

The phallus, round bodies and lymph folds lie in this chamber. The

opening to the cloacal bursa is found in the dorsal aspect of this

chamber.

The uroproctodeal fold forms the cranial boundary of the

proctodeum and the caudal boundary of the urodeum. The urodeum is Carl Edward Knight

the middle chamber of the cloaca. The ejaculatory papillae and ureters

empty into this chamber.

The uroproctodeal fold forms the cranial boundary of the urodeum

and the caudal boundary of the coprodeum. The coprodeum is the most

cranial of the three chambers of the cloaca and the rectum empties into

this chamber.

The E, sphincter cloacae, m, contractor cloacae, m. transversus

cloacae, m. levator cloacae and m, dialator cloacae are muscles directly

associated with the cloaca. Other muscles of the caudal area indirectly

act on the cloaca.

The a, pudenda interna supplies the vascular bodies and the re-

productive structures of the proctodeum. The x, pudenda interna drains

the structures and closely parallels the course of the a, pudenda

interna. The n, pudenda is closely associated with these vessels. The

cloacal ganglion was found to lie close to the vascular body.

The vascular bodies lie ventral to the cloaca and are composed of a network of capillaries. Endothelial lined channels were found originating next to the capillaries and draining to larger channels which in turn left the vascular body and entered the phallus, round bodies and lymph folds.

The phallus was found to lie in the ventral midline of the procto— deum. Stratified squamous epithelium composes its epithelium. The dermis lies deep to the epidermis with a core of connective tissue

lying deep to the dermis. The channels which originate in the vascu-

lar body extend into the connective tissue core and the dermis.

The round bodies are paired structures which lie on either side of the phallus. Their epidermis is composed of stratified squamous Carl Edward Knight epithelium. Deep to the epidermis is connective tissue which contains the channels. These channels connect with the channels entering the phallus.

The lymph folds are paired structures which lie lateral to the round bodies. Their epithelium is simple columnar and contains goblet cells. Deep to the epithelium lies the connective tissue which contains the lymph channels. These were found to connect with the phallus and round bodies. In addition numerous lymphocytes were found in the lymph fold. The lymph fold has many of the features of the lower digestive tract but lacks a muscularis mucosa.

ACKNOWLEDGEMENTS

I would like to thank Dr. A. M. Lucas, Project Leader of the

Avian Anatomy project for his assistance, guidance and use of the

U. S. Department of Agriculture facilities during the course of this study.

I would also like to thank Dr. R. K. Ringer, Professor of Poultry

Science and Physiology at Michigan State University for his assistance and constructive criticism in presenting this paper.

To Mr. Robert Ewing, illustrator for the Ayian Anatomy project,

I owe a special debt of gratitude for his excellent illustrations. His willingness to help and his tremendous talent is greatly appreciated.

I would like to thank Mrs. Sandra L. Pangborn, Avian Technologist for the Poultry Science Department and Mrs. Effie M. Dennington,

Biologist, U. S. Department of Agriculture for their help in the prepara- tion of slides used in this study and Mrs. Jean A. Fay, Laboratory

Technician, U. S. Department of Agriculture for her assistance in the labeling of the drawings.

In conclusion, I would like to express my gratitude for the patience and understanding provided by my wife, Janet, during the course of this work.

ii TABLE OF CONTENTS

Page

I ACKNOWLEDGEMENTS ...... ii

II TABLE OF CONTENTS ...... iii

III LIST OF FIGURES ...... v

IV INTRODUCTION ...... l

V REVIEW OF LITERATURE ...... 3

VI OBJECTIVES ...... 45

VII PROCEDURE ...... 46

VIII RESULTS ...... 48

Gross Description of: Cloaca ...... 48 Proctodeal Fold ...... 51 Proctodeal Cavity ...... 52 Uroproctodeal Fold ...... 53 Urodeum ...... 54 Phallus ...... 54 Round Body ...... 55 Lymph Fold ...... 57 Musculature ...... 58 Arteries ...... 63 Veins ...... ‘...... 66 vascular Body ...... 66

Histological Description of: Dorsal Lip ...... 7O ventral Lip ...... 73 Proctodeal Fold ...... 74 Arteries, Veins, Nerves and Muscles Related to the vascular Body ...... 77 vascular Body ...... 79 Lymph Channels ...... 8O Phallus ...... 82 Round Body ...... 87 Lymph Fold ...... 88

iii TABLE OF CONTENTS (continued)

Page

IX DISCUSSION ...... 92

X SUMMARY ...... 96

XI LITERATURE CITED ...... 99

iv LIST OF FIGURES

Figure Page

1. External Surface of Cloaca ...... 104

2. Cloaca with Dorsal Lip Elevated ...... 106

3. Cloaca with Proctodeal Fold Pulled Dorsally and Laterally to Expose Proctodeal Cavity ...... 108

4. Cloaca with Proctodeal Fold and Uroproctodeal Fold Displaced ...... 110

5. Stereogram of the Cloaca ...... 112

6. Muscles Related to Cloaca - Caudal View ...... 114

7. Muscles Related to Cloaca - Lateral View ...... 116

8. Arterial and Venous Supply to Vascular Body ...... 118

9. Sagittal Section through Cloaca ...... 120

10. Frontal Section through Cloaca ...... 122

11. Low Power of vascular Body Tissue ...... 124

12. High Power of vascular Body Tissue ...... 126

13. Sagittal Section through Phallus ...... 128

14. Three Dimensional Illustration Showing Connections of the Lymph Channels of the vascular Body to Those of the Reproductive Structures of the Proctodeum ...... 130 INTRODUCTION

Sperm are produced in the testis and conveyed to the urodeum through various ducts. When the bird is sexually stimulated, the semen is ejaculated out of the ejaculatory papillae and then flows down a groove which is formed by reproductive structures located in the proctodeum (the terminal chamber of the cloaca). Just after it leaves the ejaculatory papillae, the semen is diluted by a thin fluid. This thesis is concerned with the structures involved in the production and deliverance of this fluid.

Conflicting reports and terminology, insufficient information, and the lack of good illustrations of the cloacal area has created some confusion. Previous authors have dealt with various aspects of the anatomy of the cloacal area and the structures involved in dilution of avian semen. Much of the detailed anatomy has been done on birds other than the chicken. The review of literature is presented in some detail to bring terminology used by various authors together. The musculature has been reviewed extensively, as the act of coitus is intimately related to the action of these muscles. Also in studying histological sections, the muscles play an important role in determining the orientation of the tissue. Without this, the sections are very confusing and often times misleading.

The arteries, veins, nerves and lymphatics are briefly reviewed.

A.more comprehensive study of these structures is needed.

1 2

From the external surface, each item is described as it is en-

countered in each chamber of the cloaca. After a description of the

cloaca and its contents is presented, the structures related to the cloaca are described including muscles, nerves and blood vessels per-

tinent to the area. Following a study of the gross anatomy of the area

the histological characteristics, mainly of the reproductive structures,

are presented.

In reading both the review of literature and the findings of

this paper it is helpful to consult the figures presented at the end of

this thesis. REVIEW OF LITERATURE

Cloaca

A. .§£2§§ -- The cloaca, which literally means sewer, is the common receptacle for products of the digestive and urogenital systems.

It is composed of three chambers, the proctodeum (Gr. prokto-anus + hodaios - on the way), urodeum (Gr. ouron—urine + hodaios) and coprodeum

(Gr. kopros - feces f hodaios) (Stedman, 1961).

The avian cloaca is a modification of the crocodilian and saurian types of the terminal end of the digestive and urogenital tracts (Gadow,

1888). In 1829, Barkow described the cloaca of the Gallus_ga11inaceae

as having three chambers. The rectum entered the first chamber which he stated was the largest of the three. The middle chamber contained a pair of ureters and a pair of ejaculatory papillae in the male. In the third chamber, he reported an opening to the bursa of Fabricii. In the female, he found the oviduct opening into the middle chamber.

Gadow (1888) found that this three—chambered condition existed in the Ratitae, Carinatae and Anatidae which he examined, with the same

structures entering the cloaca as reported by Barkow (1829). Gadow referred to these chambers as coprodaeum (coprodeum) which is the first chamber (most cranial chamber) described by Barkow (1829), the urodaeum

(urodeum) or middle chamber, and the terminal chamber, the proctodaeum

(proctodeum). In this comparative work, Gadow described the difference between the cloacal function of various birds. He indicated that ducks,

3 4 herons and cormorants collected their feces and urine in the coprodeum.

In geese, the feces are retained in the rectum and simply passed through the cloaca, and in the ostrich, the acts of defecation and micturation are almost separate acts.

Liebe (1914) used the terminology employed by Gadow (1888) for the divisions of the three chambers of the cloaca of the duck. In the coprodeum, he described the surface as being thrown into delicate folds covered by a smooth, glandless membrane. Towards the urodeum, the folds become stronger during the transition from the coprodeum into the urodeum. The urodeum was described as being separated from the coprodeum by a well—developed ring-shaped fold with strong circular muscles in it.

He also stated that the urodeum is the smallest chamber in the cloaca, being smaller in length and also in width than the other chambers.

He stated that the penis is located in the proctodeum, and that, because of the size of the penis, the urodeum is forced into the copro— deum slightly (like a small cylinder into a larger one). The ureters in the duck are oval elevations in the urodeum with their openings being fine, longitudinal slits on these elevations. The ejaculatory ducts open into the urodeum on small cone—shaped papillae. He reported a narrow fissure leading from the urodeum to the proctodeum which continues between the two elevations that form the point of attachment of the penis to the cloacal wall. He also stated that a duct of the cloacal bursa is found entering the proctodeum.

Kaupp (1918) divided the cloaca into a coprodeal and urodeal portion but did not mention a proctodeum.

Masui (1929) also described the cloaca of the domestic fowl as consisting of two divisions, a coprodeum and urodeum, which are divided 5 by three folds. Fold I divides the coprodeum from the urodeum, fold II lies between fold I and fold III. The area between fold II and fold III was not named, but some indication was given that this area is the vestibule between the phallus and the proctodeal fold. Fold III is the largest fold and forms the anus (vent). Gibbs (1934) used the same description of the various folds reported by Masui.

Schroeder (1933) wrote a popular article on sexing baby chicks.

In this article, he presented illustrations of the cloaca of the young fowl. He based his report on the work of Masui, describing two major divisions of the cloaca. His diagrams are schematic but point out the location of the bursa, copulatory organs, ureters and general features of the cloaca. Sisson and Grossman (1953) briefly described the three divisions of the cloaca.

Calhoun (1954) reported that the cloaca of the fowl is divided into three chambers with the rectum being separated from the cloaca by a slight constriction of circular muscle which forms a somewhat circular orifice. She stated that the ureters and genital tracts open on the floor of the urodeum.

B. Histology -— Calhoun (1954) reported villi in all three chambers of the cloaca, these villi are fingerlike in the coprodeum.

They become more leaf—like, and decrease in height in the urodeum and proctodeum. The cloaca is lined with columnar epithelium which extends to the anus (vent). Pliciae circulares are present in addition to the

folds between the compartments. She also reported the presence of lymphoid and elastic elements in the tunica propria. 6

The anal (cloacal) opening was reported by Calhoun (1954) to be

lined with stratified squamous epithelium, with the underlying tunica

propria containing many papillae. 0n the inside of the lip, the epithe—

lium was reported to be thinner with the papillae of the tunica propria

being absent. She found that by the time the first fold (first fold may be the reproductive structures) was reached, the epithelium had become columnar. The muscularis mucosa was reported to be absent with

the tunica propria and submucosa fused into a thin, loosely arranged

layer.

C. Embryology —— Romanoff (1960) reviews the work of several

authors regarding the development of the cloaca. The proctodeum, he

stated, is of ectodermal origin; whereas, the urodeum and coprodeum are of entodermal origin.

The proctodeum does not become confluent with the cavity of the entodermal cloaca until the incubation period is near termination.

During its development, the proctodeum is closely associated with the cloacal bursa. The lips of the cloaca appear on the fifth day of in— cubation. The coprodeum begins its formation after the eighth day of incubation. Between the coprodeum and the urodeum, a thin membrane is found which is composed of three layers of tissue, coprodeal epithelium, urodeal epithelium and an intervening layer of connective tissue.

In addition to the urodeum being separated from the proctodeum, it was reported to be separated from the coprodeum as well. Entering the area of the future urodeum, the Wblffian ducts are found to fuse with several dorso-lateral diverticula of the gut about the third day of incubation. D. Seminal Vesicles —- In passerine birds, Wblfson (1952) re-

ported the presence of a cloacal protuberance which appears as two pear-

shaped bodies composed of tightly coiled tubules. These tubules are

connected with the ductus deferens and also to the urodeum via two small

ducts. He concluded that they are for the storage of sperm. These

structures are glandular and capable of secreting a medium for the

transport of sperm. The seminal vesicles become greatly distended and

lie outside the body cavity which he thought may explain how semen is

cooled in these birds. This idea was not subjected to experimentation.

The distension of these structures occurs during the reproductive season.

Bailey (1953) reported that fringilids possess at the end of the ductus

deferens, seminal vesicles which are derived from the mesonephric duct.

The transition between the ductus deferens and seminal vesicle was re—

ported as gradual. The vesicles increase in size in the spring and

summer and decrease in the fall and winter; this increase is as much as

thirty-fold causing the cloaca to protrude prominently. Masses of sperm

are found in these seminal vesicles throughout the breeding season. He

considered the seminal fluid and sperm to be stored in the seminal

vesicles and expelled as the ejaculate.

Marshall (1961) instead of using the term seminal vesicle, sug-

gested the term seminal sac as a more appropriate term. He also stated

.that the ductus deferens and the "seminal vesicle" are mesonephric duct

derivatives.

Bradley (1951) stated that in the fowl the ductus deferens widens

as it approaches the cloaca but did not indicate any seminal vesicle. Phallus and Round Bodies’

A. _§£g§§ -- In referring to the reproductive structures of the proctodeum various termdnology has been used. Many of these terms are homologous. Genital eminence, phallus, white body, rudimentary copula—

tory organ and penis are used to refer to a single structure. The term penis, when used to describe what is referred to in this paper as phallus is not homologous to the penis in mammals. The duck does have a large penile—like structure; whereas, the chicken has a small protuberance.

The semen from the ejaculatory papillae empty into a groove which carries the semen to the female. In mammals, however, there is a continuous duct from the testes to the outside. Gadow (1888) reported that the copulatory organ is found in the proctodeum.

Pomayer (1902) (as cited by Liebe, 1914), found that during embryonic development in the chicken, a penis-like process is laid down homologous to that in mallards, which possess-in contrast to a rooster a well-developed penis. He found also the same to be true in Corvus corone.

Gerhardt (1907) discussed the morphology of the copulatory organs of the Ratites. In 1908, he briefly discussed the copulatory organs of the Crax and Tinamus. In his work, Liebe (1914), described the penis of the domestic duck (Anas boschas domestica) as a spirally wound for-

mation which projects from the proctodeum nearly filling the cloacal opening in the erected state. The duck penis was reported to lie on the floor of the proctodeum having two firm side elevations with a sulcus between them which spirals to the tip. The channel which is formed is reported as the connection between the urodeum and the 9 proctodeum and continues as a channel on the external side of the genital organ. The two elevations which project from the proctodeum unite to form the penis and maintain this sulcus between them.

Kaupp (1915) described the male reproductive organs of birds but gave no consideration to the reproductive structure in the chicken.

Masui (1929) described the phallus of the fowl and referred to it as the white body. He described two round bodies on either side of the phallus. In the female, he reported that the white body and two round folds could not be found. This report opened up the industry of sexing baby chicks. He also found that castrated males would lose the white body.

Dove (1929) found that some White Leghorn males have a diminutive copulatory organ and that this is directly related to sterility. He found that capons lack a phallus which sterile males possess.

Masui and Hashimoto (1933) presented illustrations of the genital eminence of baby chicks giving percentages and other data on the shape of the genital eminences. They described the adult form which was similar to that previously reported by Masui (1929). They described the phallus of the day-old male chick extensively, dividing the copulatory organ into six different types (ArF) on the basis of its size and shape and illustrated each of these types. The majority of these struc— tures fell into type A (78.3%), which they classified as structures being large in size and regular in shape. The other five types composing the remaining 21.7% were found to occur with approximately equal frequency, except for type F which represented only 0.2% of the 1,327 examined. Types B—F were deviations from type A, being smaller and/or 10

having various structural differences. They pointed out that the round

bodies are extremely variable in baby chicks.

The female eminence was divided into three types A, B and D,

again based on siZe and shape. However, type A represented the group

which has no phallus present, type B has a small eminence and type D

which has the largest eminence is comparable to the eminence classified

as type A in males. The majority of the structures fell into the type

"A" category.

Gibbs (1934) reported that in sexing baby chicks the eminence

(phallus) is located in the median aspect of the urodeum of the cockerel

.and is not always present in pullets. He felt that it should be called

a shiny or glistening body and stated that it is the same general color

as the mucous membrane of the urodeum.

Gibbs also stated that the process (phallus) is situated in the

median ventral aspect of fold II which he felt limited the urodeum. He

reported enlarged folds of tissue on each side of the process which are

set obliquely to it and considered them important landmarks in locating

the process.' He stated that the best time for looking at the process

(phallus) was shortly after hatching and that after seven days it is

impossible to determine the sex of chicks with any degree of accuracy

because of the irregularities in the size of the process.

Jull (1934) studied the feasibility of sex segregation in day-old

chicks, giving percentages on the accuracy of separation of the sexes.

He made wax models showing the types of copulatory organs found in male

and female chicks and the approximate percentages of each type. He

presented his classification of male and female reproductive structures. 11

Canfield (1940) presented excellent drawings on the structure of the genital eminence of both male and female baby chicks. In addition to the illustrations of the genital eminence he presented a drawing of the proctodeal portion of the cloaca which he labeled as follows: genital eminence (phallus), round bodies, transverse fold (may be procto— deal fold), intestine (cranial wall of proctodeum). In the dorsal aspect of the drawing, the opening to the bursa can be seen but it is not labeled.

Canfield presented six illustrations for each sex. In the male, he found that as the eminence decreased in size the round bodies increased. Where the genital eminence was largest it was found to lie between the transverse folds but as it decreased, it came to lie above the transverse folds. The female eminence varied from a rather flat shaped structure to where it was completely absent.

In 1941, Canfield presented additional drawings on the variations he encountered.

Gee (1963) classified males and females into A, B, and C types.

Type A cockerels had a large eminence; type B had an intermediate size eminence and type C had a very small to absent eminence. In the females, type A lacked an eminence, type B had a tiny eminence and type C had a large eminence. He ran experiments to see if size of eminence was an inherited characteristic and concluded that there may be a complex genetic influence on these structures or that their size may be a re- flection of some other physiological property.

Earlier, Hammond and Burrows (1937) noted that some female chicks possess a male-like eminence while others have none. They thought it might be due to an inherited hormone balance. After conducting several 12 experiments they concluded that the size or type of eminence of the day- old female chick is not related to adult mortality, age of sexual maturity, rate of lay, persistence of lay, broodiness, fertility or hatch- ability of fertile eggs.

Little work has been done on the turkey in regard to the anatomy of its reproductive structures located in the proctodeum. Hammond and

Marsden (1937) described the gross characteristics of the turkey phallus.

They stated that it is located in the ventral wall of the vent and in the male poult there are two firm hemiellipsoidal papillae, one on each side of the midline. The papillae in the male are frequently engorged with blood which make them stand out from the surrounding tissue. In the males, the papillae are quite small in some cases and can be con— fused with the tiny papillae found in a few females. The sex of the turkey can be determined at any age by examination of the genital eminence.

Blitz (1939) stated that in the turkey, the phallus is larger than that of the chicken and terminates in a double apex.

Nishiyama (1950) reported that variations occurred in the round bodies which lie on either side of the phallus. He classified them into three types.

Type 1 where the folds are lengthened laterally on both sides of the phallus.

Type 2 in which the round folds are lengthened longitudinally.

Type 3 where the round folds are similar to those in l and 2 but in addition they have small folds attached laterally to them. This additional tissue is similar in appearance to the tissue of the lymphfold. ~ 13

B. Histology —— Masui (1929) described the white body or genital eminence (phallus) as consisting of loose connective tissue containing a large amount of elastic fibers which are usually arranged in bundles.

He found many small cavities in the body which gave the appearance of the corpus cavernosum of the mammalian penis. He indicated that he was

not sure that the blood vessels opened into these sinuses. No fat was found in his examination of the structure. He reported finding vater—

Pacini corpuscles which were abundant in the round fold of fold II and in the white body.

C. Embryology -- Masui and Hashimoto (1933) reported the presence of a genital eminence and pointed out that it not only exists in the adult but also in the baby chick. They traced the genital eminence in the embryo, describing it in the early periods of growth as a ring— shaped swelling which contains in the center a tongue-shaped structure, the phallus. The male and female genital eminence appear similar in structure up to the fourteenth day of incubation. 0n the twelfth day of incubation, the shape of the genital eminence begins to change with depressions appearing on each side of the tongue-shaped papilla (phallus).

On the thirteenth day, the genital eminence is found to be distinctly divided into three portions, a cephalic (phallus) and two basal portions

(round bodies). 0n the fourteenth day, a sex difference was reported and this difference increased until the time of hatching. The phallus and the two round bodies were regarded as the organ of copulation in the fowl by Masui and Hashimoto (1933).

MacDonald and Taylor (1933) in a more detailed study on the embryology of this area indicated that at four days there is no sign 14

of a phallic knob. At five days, there is a slight indentation between

the allantoic stalk and the tail bud. At six days, they observed the

first indication of the phallic knob which is due to a thickening of

the ectoderm. This structure continues to enlarge to the eleventh day

without any structural morphology that identifies its sex. At this

stage it was observed as an external structure blocking most of the

opening. Examining the structure microscopically, a slight groove was

found in the center giving it a bilobed appearance. After twelve days,

the phallic knob began to show macroscopically two types of development.

By the fourteenth day, a knob was found surrounded by a collar of

tissue. The male structure was larger than that of the female. This

finding was similar to that of Masui. This organ continued to develop

in the male until it assumed the adult form. The female merely main-

tained a slight projection in the center of the surrounding collar.

Accessory Reproductive Structures

A. .QEEEE." The accessory reproductive structures in the male domestic chicken have been defined by Nishiyama (1955) as consisting of

two paired structures, the vascular bodies and the lymph folds.

Work on similar structures, in other birds, has been reported by

several authors (Barkow, 1829; Eckhard, 1876; Mﬁller, 1908; Liebe, 1914) prior to Nishiyama's work.

Barkow (1829) reported that in the male duck the corpora cavernosa

are strong and are located separately from each other behind the papillae

located in the middle cloacal partition.

Liebe (1914), in his work on the duck penis, described the pres-

ence of a reddish-brown structure which he referred to as the 15

"Gefabreiche Kbrper", in the centers of lymph formation. These centers of lymph formation lie at the base of the phallus and during erection project into the basal part of the phallus. The vascular bodies within these centers were found to lie between the urodeum and the cloacal sphincter. Nishiyama (1955) found that in the chicken the vascular body occupied a similar position.

The vascular body was found to be separated from the surrounding tissue by a delicate membrane (Liebe, 1914; Nishiyama, 1955) and is 7 mm in length, 1 mm in thickness and 17 - 40 mg (27.6 i:2.9 mg) in weight

(Nishiyama, 1955). In a three~month-old cockerel, the vascular body appears pink in color and weighs eight mgs. The vascular body is usually bean to egg shaped.

Nishiyama (1950a) concluded that the vascular body is part of the ejaculatory mechanism. By injecting gelatin into the vascular body he found that the lymph fold and the lymphatic vessels lying along the g, pudenda interna became distended with the injection mass.

Nishiyama (1955) reported that the vascular bodies are composed of lymphoid tissue containing numerous capillaries which are connected to the larger blood vessels found in trabeculae which penetrate the tissue. To the outside the peripheral lymph sinuses connecting to the internal lymph sinuses are found. The peripheral lymph sinuses are located between the vascular body and the connective tissue which surrounds it. The lymphoid tissue and sinuses extend up to the base of the phallus but only the sinuses were reported to enter the phallus.

Lake (1957) published an article on the male reproductive tract which conflicted with some of the statements made by Nishiyama (1955).

Lake quoted Nishiyama (1955) as stating that the vascular bodies were 16

found as two discrete bodies surrounding the base of each ejaculatory

duct only. This statement, I was not able to confirm by reading

Nishiyama (1955).

The Brown Leghorn cock used by Lake (1957) was reported to have vascular bodies forming an almost continuous ring of tissue around the base of the ejaculatory ducts. The vascular bodies were reported to form a ring of erectile tissue which was located behind the ejaculatory ducts and encircled the posterior aspect of the urodeum. Lake stated

that the vascular body, lymph fold and phallus, along with the erectile

tissue and ejaculatory ducts formed the organ of copulation. From

Lake's (1957) illustration, the vascular body appeared to project into

the lumen of the cloaca like the phallus or round bodies.

Nishiyama (1961), in response to Lake (1957), wrote another article on the vascular body to clarify the situation. In this work,

Nishiyama pointed out that "Lake errored in the anatomy and anatomical location of the vascular body", for according to his description, he considered "the second fold of the cloaca” or the fold between the urodeum and proctodeum to be the vascular body.

B. .Histology -- Lake (1957) described the vascular bodies as having a surface epithelium of pseudostratified columnar epithelium with glands extending down into the submucosa containing many goblet cells. He described the lymph folds as being covered with pseudostratified columnar type epithelium with no submucous glands. He located blood sinuses in the lymph fold but they were not as extensive as in the vascular body. He also found smooth muscle fibers present beneath the basement membrane of the epithelium. 17

Lucas and Stettenheim (1965) stated that the vascular body was a mass of capillaries with very little parenchymal tissue. They recom- mended the term corpus_paracloacalis since Barkow (1888) and others

used the term corpus cavernosum to refer to large sinusoidal erectile

tissue associated with the phallus or ejaculatory duct in birds which have a large phallus which is not found in the chicken.

The lymph fold was reported by Nishiyama (1955) to be composed of two spindle-shaped folds being about 2.8 x 1.2 mm in size and covered with columnar epithelium. The submucosa consists of loose connective tissue containing many lymph sinuses which connect with the sinuses of the phallus. He also reported that they connect below to the vascular bodies. Nishiyama (1955) found the epithelium of the lymph fold to be glandular, as many secretory granules were found in the cells.

Erection

Burrows and Quinn (1937) described the ejaculatory process which they reported to last but a few seconds. To enable them to better appreciate the structure of the erected phallus, they clamped the organ at its base to keep it in the erected state. In addition, they mentioned the anatomical location of the phallus in relation to the cloaca.

They reported that there are two areas of erectile tissue, one on each side of the midline. The erected phallus was reported to be a heart— shaped, varying in size from 0.5 mm x 1.2 mm to 2 mm x 2 mm. The ejaculatory papillae are not directly connected with the phallus but are intimately associated with it. They described the location of the ejaculatory papillae indicating that the papillae enter the dorsal wall of the large intestine in close association with the ureters but do not 18 pierce the inner wall at that level. The ducts transverse the dorsal

quadrant of the internal sphincter and enlarge into a bulbous pocket.

Nishiyama (1950a) discussed the mechanism involved in the erec-

tion of the copulatory organ. He found that the lymph is separated from

the blood in the vascular body and then fills up the lymph channels with

fluid. The excess lymph which is not excreted flows back to the lymph duct lying along the 2. pudenda interna. He stated that the round

bodies are the structures which mainly become distended with fluid and consequently the phallus is thrust caudally and downwards. In addition, the m. levator cloacae (§.m. retractor penis posterior) relaxes. In

the erected state, Nishiyama (1950a) reported that the round folds are in contact with one another forming a groove which the ejected semen runs through. Lymph folds also were found to swell up and he considered them accessory organs of the phallus. He found that in the castrated male, the vascular body and lymph fold degenerate.

Nishiyama (1951b) was not sure where the transparent fluid from the vascular body came through the epithelium of the proctodeum but he stated that it seemed to be ejected at the time of c0pulation.

Nishiyama (1951a, 19523, 1952c) worked on various aspects of the transparent fluid. He reported that the lymph flowed through the inter- cellular Spaces of the epithelium of the lymph fold. He presented photomicro— graphs of an injection media passing through the columnar epithelium of the lymph fold and into the proctodeum.

Nishiyama (1961a) discussed the ejaculation of transparent fluid during c0pulation presenting excellent information on its origin and extrusion. Nishiyama (1961b) presented further information on the 19

effects of the masSage method of collecting semen on the flow of trans-

parent fluid.

Muscles

A. _M. Sphincter Cloacae -- The E: sphincter cloacae was described

by Liebe (1914) in his study of the duck (Anas boschas domestica) re—

ferring to the muscle asyg,_§phincter cloacalis. He described the

muscle as being composed-of two distinct layers, an external portion and

an internal portion. This double layered arrangement does not continue

into the base of the muscle; at the base, it consists of only the internal

layer.« He pointed out that the overlying skin grows in close association

with the 2' sphincter cloacae near the anal (cloacal) opening.

Porta (1908) referred to the E: sﬂincter cloacae as the _u_:.

sphincter ani. In turkeys and peacocks, he described the muscle as

being composed of circular fibers which continue around the anal (cloacal)

aperture.

Earlier Gadow (1888) described the E: sphincter cloacae for

various birds, Rhea, Casuarius, and Struthio. Gadow stated that the

muscle does not have any attachments to the skeleton and that a few

muscle slips are attached to the flexor muscles of the tail and to the

skin in which the tail feathers are lodged. Without drawing a conclu—

'sion here, the possibility exists that he was referring to thegp.

levator cloacae.

Du Toit (1913), in his study of the chicken, added little con-

cerning this muscle, referring to it as Eb sphincter ani. He did say

that the muscle is broad and flat dorsally. ventrally, it is solid and

thick. 20

The two terms 2: sphincter cloacae and the E: sphincter ani have

been used by authors in the past. The selection of the better term is dependent on the definition of cloaca and anus.

The term 2. sphincter cloacae as presented by Liebe is considered

to be the most appropriate term to describe this muscle as the definition of anus according to Dorland (1959) is "the distal end and outlet of the alimentary canaPL A cloaca (Dorland, 1959), "is an opening or cavity at the posterior end of the body of a vertebrate into which the intestinal, urinary, and reproductive ducts open". It would seem, therefore, more anatomically sound to use the term, Er sphincter cloacae for the name

of the muscle surrounding the cloacal opening and leaving the term

39 pphincter ani for the vertebrates which have a distinct separation

between the digestive and the urogenital systems.

B. .M. Contractor Cloacae -— Du Toit (1913) proposed the term,

g; contractor cloacalis. In this paper, the ending of the term cloacalis

has been changed from alis to_§g,thus changing the adjective cloacalis to a noun cloacae which is, in Latin, in the genitive case. The term, m. contractor cloacae, now reads contractor muscle of the cloaca.

Porta (1908) described this muscle in the turkey briefly but referred to it as the Er transverso-cloacalis as did Gadow and Selenka

(1891). Du Toit (1913) pointed out this discrepancy and after considera— tion of this muscle I am in agreement with Du Toit as the term g. transversus cloacae described by others is a completely different

muscle.

Porta (1908) described the.gh contractor cloacae as completely

surrounding the cloaca with relationships with the m. sphincter ani

(cloacae) and ends of the pubic bones. He described this muscle briefly with little detail. Du Toit (1913) more adequately described the extent of the m. contractor cloacae in the chicken. He stated that it forms a

continuous ring around the E: sphincter cloacae. Dorsally, the muscle

fibers are in close association with those of the E: sphincter cloacae

but as it passes ventrally, it separates from the sphincter muscle, coursing to its insertion on the pubic bones. For its function, he stated the contraction of this muscle exerts a*strong compressing force on the cloaca.

C. EL levator cloacae —- Porta (1908) described the g; levator

cloacae in the turkey and peacock, referring to it as the m. suspensor ani. He described the muscle as originating from the capsule of the most lateral rectrix and then passing to the.gy sphincter cloacae under the g. contractor cloacae.

Du Tbit (1913) described the m. levator cloacae in some detail

for the chicken. Like Porta, Du Toit reported that the muscle originates from the ventral border of the most lateral rectrix. The muscle is found medial to the g. depressor caudae, originating from connective tissue. The muscle he described is delicate, 0.3 - 0.5 mm in cross- section. It passes under the posterior margin of the.gy contractor

cloacae, and continues caudally under the E: contractor cloacae and then under the 9. sphincter cloacae, lying medial to these two muscles and lateral to the mucous membrane of the cloaca. The muscle then joins its homolog from the opposite side in the midline and together they form a complete noose or loop around the cloacal opening.

Liebe (1914) referred to the m. levator cloacae muscle in the duck as the m. retractor penis posterior. His description of the muscle 22 is similar to the description of Du Toit (1913) and Ports (1908).

Liebe (1914) stated that it is circular in shape near its origin being about 4 mm in cross section but becomes flattened as it proceeds towards its insertion at the base of the m. sphincter cloacae. Liebe stated

that it passes beneath the m. sphincter cloacae to the basal part of

the penis where the center for lymph production is found. At this point, he found that it curves toward the ventral wall of the cloaca close to the ventral median line. The muscles from each side almost touch. Liebe (1914) stated that the muscle acts as a retractor of the basal portion of the penis. Since this muscle in the duck is similar in structure to the muscles in various other avian species, it does not seem necessary to introduce the term 2. retractor penis posterior. It may retract the penis.but it may also be involved in elevation of the cloaca. The term m. levator cloacae which is more inclusive is used in

this paper to refer to this muscle. M. suspensor cloacae may have some

merit. Gadow (1889) used the term m. levator ani. Fisher (1946) used

the term 2. levator cloacae to refer to this muscle, which is thought

to be justified as it describes the action of the muscle and the area which it is acting on, while .9.- suspensor cloacae indicates that the

muscle's function is to suspend the cloaca from the tail. This is only part of its function and the term 2. levator cloacae indicates the more

active function of the muscle, the elevation of the cloacae.

IL 3; transversus cloacae —— Another muscle of the cloacal muscu-

lature is the Pl- transversus cloacae. Gadow (1888) referred to this-

muscle as 93 transverso—analis. The origin of the muscle in the birds

he studied was from the distal caudal ends of the pelvic bones. Their 23

insertion was in the midventral line via an aponeurotic junction with

its homolog from the opposite side. They are also attached to the

anterior margin of the anal (cloacal) opening where they were found to blend with the m, sphincter cloacae.

As indicated in the description of the E: contractor cloacae,

Porta (1908) was referring to the E: contractor cloacae rather than the

3y transversus ani when employing this term. His photographs show that

what he referred to as the E: transversus ani is in reality thegp.

contractor cloacae.

Du Toit (1913) gave an excellent description of the E: transverso- analis (M. transversus cloacae). He described the muscle as originating

from an aponeurotic fascial sheet, which arises from the anterior caudal vertebrae and from the posterior iliac spine of the pelvis. At the latter point, it appeared as a muscle. From that point ventrally, he found that it passed in a slight arc to the anterior margin of the musculature surrounding the cloacal opening. Its fibers in the midline fuse with the.gy sphincter cloacae and the aponeurosis of the abdominal

wall.

Liebe (1914) found that the muscle originated at the dorsal aspect of the proximal one—third of gs pubis in the duck. It embraced

the ventral part of the Ev sphincter cloacae and attached to the lateral

and posterior part of it with some of the fibers running into it. He referred to the muscle as 35 transversus cloacalis.

Burt (1930) referred to this muscle as the m. transversus perinei in the woodpecker.

The foregoing authors presented muscles which were similar in origin and insertion in different species. Porta (1908) used similar 24

terms for different muscles. The term 2: transversus cloacae is con-

sidered to be the appropriate term to use as this muscle is associated with the cloaca rather than the anus which the other terms indicate.

E. “M. Dialator Cloacae —— Porta (1908) described the Er dialator

cloacae as arising from an aponeurosis which embraces the posterior part of the M. lateralis coccygeus and then courses lateral to the 91°

depressor coccygis, under the E: contractor cloacae and then spreads to

the E: sphincter cloacae.

Du Toit (1913) referred to this muscle as Eb dialator ani. He

reported that often this muscle did not exist or showed atypical formation. He stated that it arose from the middle of the outer edge of the ishium from a tendon but its origin was difficult to observe. Its cranial surface was covered only by peritoneum.- On the caudal surface, it was covered by E: lateralis coccygis. The muscle was reported to

course in a straight direction from its origin to the lateral edge of the cloaca. Its function, according to Du Toit (1913) was to expand the anal (cloacal) opening and also to act as a retractor of the anus

(cloaca) together with the Er suspensor ani Q3. levator cloacae).

Liebe (1914) described the muscle in the duck as originating from the bony pelvis, passing straight backwards closely adjacent to the pp depressor caudae and finally merging on each side of the E: sphincter

cloacae, into the dorsal wall of the center for lymph formation. He reported that,the Er dialator cloacae ramifies, forming a larger and

smaller portion of the muscle. The small portion of the muscle passes caudally to the fibrous tissue surrounding the vascular body and attaches there. The larger portion of the muscle turns diagonally downward and inserts at the base of the penis. 25

The E, dialator cloacae is a new term. By changing Porta's term

ani to cloacae, this name becomes more descriptive of the actual area

it is acting on. Liebe's (1914) term (_. retractor_pgnis posterior) has

merit when referring to the duck but the implication of function by the

term 2: retractor_penis_posterior does not apply to the chicken.

F. M. lateralis coccygeus -- Parts (1908) reported that this

muscle has its origin on the posterior and superior border of the pubis.

The muscle passes from its origin under the g,_pubo-coccygeus externa

to the body of the last caudal vertebra.

Du Toit (1913) found that this muscle originates from the lower

two-thirds of the ischium and from the end of the pubis. He described

it as a fan-shaped muscle at its origin, forming a thick bundle toward

its insertion on the cranial part of the lower area of the pygostyle.

This muscle appears very similar to the muscle found in the duck.

Liebe (1914) described this muscle in the duck, stating that its

origin from the internal surface of the pp pgp£s_and adjacent part of

the _<_>_s_ ischii was covered by the M. pubo-cocpygsusexternus, E' transversus

cloacae and the long head of the caud-ilio-femoralis (E: lateralis

caudae). He reported that the muscle passes diagonally backward and upward where it becomes narrow, ending in the skin of the posterior area of the coccyx. The internal surface of the muscle lies on the peri-

toneum.

Burt (1930) referred to this muscle as the g, lateralis coccygis,

as did Fisher (1946). In the Woodpecker, the g. lateralis coccyggs originates from the inner surface of the posterior portion of the ilium

and as far anterior as the first free caudal vertebrae. The muscle

J 26

inserts on the anterior surface of the lower one-half of the disc of

the pygostyle.

In the raven (Shufeldt, 1890), the E: lateralis coccygis origi— nates from the ilium and inserts on the posterior margin of the pygostyle

exclusive of the midspine.

Fisher (1946) stated that in the new world vulture, this muscle originates from the posterior ventral surface of the ilium and the

transverse processes of the first three free caudal vertebrae. The in—

sertion is to the ventrolateral corners of the anterior two—thirds of

the pygostyle. This muscle in the Whooping Crane (Grus americana:

Fisher, 1955) has a similar origin and insertion.

EL lateralis coccygeus is considered here to be the term which

more completely describes this muscle. The term, 2: pubi-cocgygeus

interna is an appropriate term for this muscle in the chicken and duck.

However, in some birds this muscle does not originate from the pubis.

Therefore, because of the inclusiveness of the term_M. lateralis

coccygeus, it will be used in this paper.

G. 'M. Depressor Caudae —- Porta (1908) referred to this muscle

as the M. pubi-coccygeus externa. It has a similar origin and insertion

in the duck as in the chicken and turkey. He added that fibers of the pp obliques abdominus externus mix with the fibers of the E: depressor

caudae at its origin. The fibers of the E: depressor caudae internally

mix with the M. transversus abdominus.

Kblda and Komarak (1958) referred to this muscle as thegp. ppbi-coccygeus externa. Their description is in agreement with the

deacription presented by Du Toit (1913), except in their consideration 27 of the insertion which they said was attached to the mobile coccygeal vertebrae. They referred to its action as depressing the tail.

Shufeldt (1890) referred to this muscle as the.Ep depressor caudae.

He described it as a strong conical muscle which was devoted to pulling

the tail down and laterally if it contracted individually and directly downward if it contracted with its companion muscle. Its origin was described as being similar to the origin in the chicken. Its insertion is at the base of the third or fourth outer rectrix.

Burt (1930) described the muscle as arising not only from the pubis but also from the ishium. The insertion is described as being at

the base of the fifth tail feather.

The term, 9} depressor caudae, is used in this paper as it ex-

presses the function of the muscle. 'M. pubi-coccygeus externa is a

term which has merit but the muscle fibers attach to the base of the tail in most cases rather than to the coccygeal vertebrae.

Other muscles of the tail not directly related to the cloacae itself are described here briefly to complete the description of the caudal area.

A. _M. levator coccygis -- The E: levator coccygis was described

by Shufeldt (1890) in his studies of the raven. He found that it arose on the ilium just beyond and to the side of the anterior free caudal vertebrae. The fibers, he reported, converge and end in a tendon which inserts on the tuberosity on the anterior margin of the pygostyle. He also stated that the muscle gives off various fibers to the other caudal vertebrae. According to Shufeldt (1890), age and muscular development play a role in the extent the muscle encroaches on the pelvis. The 28

older and more developed the muscle, the more extensive the area of

origin.

Porta (1908) reported that in the turkey and peacock, the muscle originates from the superior and posterior part of the ilium and on the

sacrum. Its insertion is on the spines of the first six caudal vertebrae.

Its function is to elevate the tail. He also stated that the E: levator coccygeus is considerably larger in these two species than in all the other Gallinaceae. Special mention was made of the large size of this

muscle in the peacock.

Du Toit (1913) described the muscle as being composed of two parts, an upper and lower. The upper part arises from the diapophysial plate and neighboring parts of the ilium. The lower portion arises from the transverse process of the last synsacracaudal vertebra and the first, second, third and fourth caudal vertebrae. The muscle inserts on the pygostyle and functions to raise the tail.

Burt (1930) gave a description of the E: levator cocqyg;s_in the woodpecker. He stated that it arises from the superior surfaces of the transverse processes of the free caudal vertebrae but not the pygostyle and also from the ilium on each side of the mid-dorsal line extending anteriorly to a point just beyond the acetabular region. It inserts by tendons to each of the neural spines of the free caudal vertebrae and to each side of the anterior edge of the large neural spine of the pygostyle. In addition, he pointed out that this was the largest muscle of the dorsal tail musculature and the principle elevator of the tail. The muscLe in the woodpecker is pointed anteriorly and becomes progressively larger as it moves posteriorly until it reaches the ilium where the fibers converge to form the large tendon which in— serts on the pygostyle. 29

Fisher (1946) in his work on the new world vultures, found that

the E: levator coccygis consists of three bundles. The origin is along

the median dorsal surface of the ilium and the transverse processes of the fused sacral vertebrae beginning with the third vertebra posterior to the acetabulum. It inserts via tendons to the anterolateral surfaces of the neural spines of the free caudal vertebrae and the pygostyle and has a fleshy insertion on the first free vertebrae.

In the Whooping Crane, Fisher (1955) found that the origin is tendonous anteriorly from the dorsal surface of the sacrum. The origin extends posteriorly onto the transverse process of the first free caudal vertebra but was fleshy in the caudal half of its length. The muscle was again composed of three parts which had separate insertions. The most medial bundle inserted on the lateral surface of the dorsal spine of the third caudal vertebra. The middle bundle went to the same position on the fourth-vertebra and the lateral fasiculus went to the fifth free vertebra. Liebe (1914) only mentioned the E: levator coccygis in the duck.

Kblda and Komarek (1958) found in the domestic fowl that the E: levator coccygis arises as in other species of birds from the ilium and was divided into two parts, an upper part which inserts on the pygostyle and a lower part which inserts on the transverse process of the mobile coccygeal vertebrae.

All authors seemed to be in agreement with the term g. levator coccygi .

B. M. lateralis caudae -- M. lateralis caudae was described by

Shufeldt (1890). He reported that part of the muscle originates from 30

the tip of the transverse process of the first free caudal vertebra and

it inserts on the outer side of the external rectrix of the tail. Other

bundles of this same muscle originate from the tips of the transverse

processes of the next three caudal vertebrae and insert on the base of

the first two or three outer rectrices.

The combined mass of muscle acts to pull the feathers down and

laterally. The lateral bundle alone will have a tendency to pull down

and separate the rectrices.

In the woodpecker, Burt (1930) described the muscle as arising

from the ends of the transverse processes of the last four free caudal vertebrae and inserts by tendons into the third, fourth, fifth and sixth rectrices. Contraction, he stated, pulled the rectrices laterally.

EL ilio-coccygeus, referred to by Du Toit (1913) was a synonym

for the g. levator caudae. He stated that this was not a good term and

he retained it to maintain continuity with Gadow (1891).

Du Toit (1913) reported that this muscle in the chicken appears as one of the dorsal muscles but actually belongs to the ventral muscula—

ture. The origin is fleshy from the fifth synsacrocaudal vertebra, the dorso-medial area of the ilium, and the first and second caudal vertebrae.

The muscle inserts on all the tail feathers except the inner ones. Its function is to lift the tail feathers.

Liebe (1914) referred to this muscle as the E: ilio-coccygis. He

stated that its origin is from the ilium and transverse processes of the caudal vertebrae and its insertion is on the fourth or fifth rectrix.

QM. lateralis caudae was used after Shufeldt, as the terms intro-

duced by other authors did not seem adequate to describe the muscle in other birds. 31

C. M. levator caudae -- M. levator caudae in the raven was

described by Shufeldt (1890) as a long, oblong muscle, larger than the pp levator coccygis and lying immediately to its lateral side. The muscle was found arising from the posterior portion of the pelvis but not as far forward as the E: levator coccygeus. He also found that it

originates from the superior surfaces of all the vertebrae of the tail except the pygostyle. He found that it inserts at the base of the four rectrices which lie in order next to the pygostyle. This insertion pro- vides the power of forcibly elevating these four rectrices when it con— tracts.

In the woodpecker, Burt (1930) found that this muscle arose from the transverse processes of the last four caudal vertebrae and inserted as in the raven at the bases of the four central rectrices on each side of the pygostyle. Its function is to elevate the tail.

In the vultures, Fisher (1946) reported a similar origin of the muscle to that of the woodpecker arising from all the free vertebrae.

It also has a similar insertion having tendons which courses to the dorso-medial corners of rectrices 2, 3, 4, and 5.

In the Whooping Crane, Fisher (1955) found a similar location of the muscle but a slight variation in location of its origin and insertion.

The muscle was reported to come from transverse processes of the fused caudal vertebrae, the dorsal surface of the transverse processes of the last fused vertebrae, the first three unfused vertebrae of the tail and some of the fascia lying between the transverse processes. Its insertion, he reported, is on the neural spine of the fourth free vertebra, the anterio—lateral corner of the pygostyle and the ventro-lateral 32

surfaces of the major upper coverts and the dorsal surface of the five

or more pairs of medial rectrices.

Liebe (1914) in the study of the duck indicated that the origin

is on the distal part of the ilium and the transverse processes of the

caudal vertebrae and it inserts on the fourth or fifth rectrix. He

referred to it as the p, ilio-coccygeus.

Du Toit (1913) did not consider this as a separate muscle but

part of the p, ilio-coccygpus.

D. 'M. depressor cocgygeus -- Shufeldt (1890) described this

muscle in the raven indicating that it arises from the lower half of

the posterior margin of the ischium and from the anterior three-quarters

of the posterior margin of the pubis. The fibers of the muscle join with those of its homolog and insert on the thickened edge of the

pygostyle.

Porta (1908) described this muscle in the turkey and peacock and

indicated that this muscle arises from a more extensive surface than is

found in all other Gallinacea. Its function, he stated, is to lower

the tail.

Du Toit (1913) reported that this muscle in the chicken is found

on the ventral side of the tail vertebrae. Its origin is from the first

tail vertebra and the synsacro—caudal vertebrae. Inside the abdominal

cavity it is covered only by peritoneum. It is covered caudally by the pp depressor caudae. It inserts on the lower edge of the pygostyle and

from this point fibers fan out and go to the tail feathers. Its function

is to pull the tail down. 33

Liebe (1914) mentioned this muscle. Burt (1930) described the origin of this muscle. His description was similar to that given by

Shufeldt. Its insertion is on the p, semitendinosus and the upper half of the lower border of the pygostyle. He stated that this is one of the largest depressors of the tail. It pulls the tail feathers downward and laterally when acting alone.

There appears here to be no conflicting terms, so pp depressor coccygeus is used in this paper to refer to this muscle.

E. Musculus adductor rectricum —- Musculus adductor rectricum

was mentioned by Du Toit (1913) and was found close to the surface of the tail starting from the caudal third of the ventral plate of the pygostyle and ran toward the caudal edge of the tail. He found the muscle generally embedded in fat and connective tissue. It inserted at the boundaries of the tail feathers. Its function was given as the contraction of the tail feathers.

Terminology of Muscles and Their Synonyms

_M. sphincter cloacae Knight, 1967

Syn: p; sphincter anale Gadow, 1888 p_ sphincter ani Gadow & Selenka, 1891 Porta, 1908 Du Toit, 1913 Liebe, 1914

_M. transversus cloacae Knight, 1967

Syn: transversus analis Gadow, 1888 Ia Gadow & Selenka, 1891 Kolda & Komarek, 1958 p, transversus ani Du Toit, 1913 pp transversus cloacalis Liebe, 1914

p, transverso perinei Burt, 1930

_M. contractor cloacae Knight, 1967

Syn: m. transverso cloacalis Gadow & Selenka, 1891 Porta, 1908 p, contractor cloacalis Du Toit, 1913

levator cloacae Fisher, 1946 L: Fisher & Goodman, 1955 Knight, 1967

Syn: levator ani Gadow, 1888 La Kolda & Komarek, 1958 . suspensor ani Porta, 1908 Du Toit, 1913 m. retractor_p§nis posterior Liebe, 1914

.H‘ dialator cloacae Knight, 1967

Syn: pp dialator ani Porta, 1908 Du Toit, 1913 m. retractor penis anterior Liebe, 1914

M. adductor retricum Du Toit, 1913 Fisher, 1946 Fisher & Goodman, 1955 Knight, 1967

Syn: p, opponens rectricio caudae Perrin, 1875

M. levator coccygis Shufeldt, 1890 Gadow & Selenka, 1891 Porta, 1908 Du Toit, 1913 Liebe, 1914 Burt, 1930 Fisher, 1946 Fisher & Goodman, 1955 Ko1da & Komarek, 1958 Knight, 1967

Syn: pp levator caudae superfecialis Perrin, 1875

M. levator caudae Shufeldt, 1890 Burt, 1930 Fisher, 1946 Fisher & Goodman, 1955 Knight, 1967 35

Syn: p, levator caudae profundus Perrin, 1875

pp iliococcygis Gadow & Selenka, 1891 Du Toit, 1913 Liebe, 1914

M. lateralis caudae Shufeldt, 1890 Burt, 1930 Fisher, 1946 Fisher & Goodman, 1955 Knight, 1967

Syn: p, iliococcygis (part) Du Toit, 1913 Liebe, 1914 p, coccygeus_quadratus Perrin, 1875

_M. depressor caudae Shufeldt, 1890

Burt, 1930 Fisher, 1946 Fisher & Goodman, 1955 Knight, 1967

Syn: p, pubi coccygeus externus Gadow & Selenka, 1891 Porta, 1908 Du Toit, 1913 Liebe, 1914 Kolda & Komarek, 1958 pp depressor coccygis Shufeldt, 1890 Gadow & Selenka, 1891 Porta, 1908 Du Toit, 1913 Liebe, 1914 Burt, 1930 Fisher, 1946 Fisher & Goodman, 1955 Knight, 1967

Syn: p, depressor coccygis proprius Kolda and Komarek, 1958

p, depressor caudae superficialis Perrin, 1875

_M. lateralis coccygis Shufeldt, 1890 Burt, 1930 Fisher, 1946 Fisher & Goodman, 1955 Knight, 1967 36

Syn: pp pubo coccygeus interna Gadow & Selenka, 1891 p,_pubi coccygei internus Porta, 1908 ;p, pubi coccygeus internus Du Toit, 1913 pp pubi coccygis interna Liebe, 1914 p, pubi coccyeus interna Kolda & Komarek, 1958

Arteries

The aorta of the White Leghorn fowl, according to Westpfahl

(1961) arises from the left ventricle and then passes to the right, forming an arch arcus aortae. The aorta continues caudally after

leaving the arch, supplying branches of the regions of the thorax and

,abdomen and was referred to by Westpfahl (1961) as the aorta descendens.

The aorta descendens terminates when it bifurcates into the paired_p.

ischiadica (Westpfahl, 1961). These vessels provide the main arterial

supply to the legs.

The aorta descendens actually continues caudad past the origin

of the_p. ishiadica. This continuation was given the name_p. sacra media by Barkow (1829). The_p. sacralis media (Westpfahl, 1961) was

reported to continue caudally giving off paired branches to the dorsal musculature. These branches were referred to as the p, pacrale§_by

Westpfahl (1961).

The p, sacralis media was reported by Kaupp (1918), Sapy (1941),

and Westpfahl (1961) to divide just caudal to the hind lobe of the kidney. Du Toit (1914) reported that it divides at the level of the fifth sacrocaudal vertebra and the first caudal vertebra. The first branch which is formed is the_p. coccygea media (Liebe, 1914; Westpfahl,

1961). This vessel is a continuation of the p, sacralis media caudally.

The paired p, pudenda communis (Du Toit, 1913; Liebe, 1914) are the other branches. Barkow's (1829) description stated that the p, sacra u———--—-‘-— 37 media gave off the unpaired p, cosgygeus communis and two 3, hypogastrica.

These terms are synonyms of the terms employed by Du Toit (1913) and

Liebe (1914).

The_p, sacralis media was reported to give off the p, mesenterica

caudalis (Sapy, 1914; Westpfahl, 1961) just before it branches into the p, pudenda communis. Other terms used, referring to this same vessel are the p, mesenterica_ppsterior (Liebe, 1914) and p, mesenterica

inferior (Du Toit, 1913). Westpfahl (1914) stated that the origin of this vessel was at the level of the last sacral vertebrae and that the p, pudendalis, (s._p. pudenda communis) arose just a few millimeters

away. Liebe (1914) and Sapy (1941) reported that in the duck the_p. mesenterica caudalis arose from the p, pudenda communis dextra.

Kaupp (1918) stated that the_p. pudenda communis after originating

from the p, sacralis media passed across the dorsal margin of thelp.

depressor coccygis giving off various rami. He reported that it then crossed the ureter giving off a branch to the p, depressor coccygeus

lateralis. On the lateral rim of this muscle, he found an artery to the bursa p, hemorrhoidalis interna and to the end of the cloaca. The p.

pudenda communis continued dividing into the p, pudenda externa and in ducks, the_p. profunda_penis. These branches supplied the vas deferens,

ureter, cloaca, penile structures and muscles of this area.

Westpfahl (1961) referred to the p, pudenda interna as the branch which arose from the aorta.

Barkow (1829) described the continuation of the p, hypogastrica

(g._pudenda communis) as the p, pudenda interna which he reported to supply the corpora cavernosum in the male. In the female, he stated

that it supplied the ureters and vagina. 38

Du Toit (1913) stated that p, ppdenda interna (visceral branch,

Sapy, 1941; Ramus intestinalis, Westpfahl, 1961) arose from the_p.

pudenda communis along with the p, pudenda externa (parietal branch,

Sapy, 1941; muscular rami, Westpfahl, 1961). The latter went to the

tail musculature. Liebe (1914) found in the duck that p, pudenda

communis sent off a weak branch shortly after it crosses with the

ureter; the p, haemorrhoidalis infirma which supplied part.of the cloaca

and bursa. A short distance from the origin of this vessel, the_p,

pudenda externa and p, pudenda interna originate. Liebe (1914) gave for

a synonym for p, pudenda interna, the term p, profunda penis which fol-

lowed the course of the ureter to the cloaca supplying the vas deferens

and the ureter as it passed caudad. He described the pp'pudenda interna

as passing through the vascular body forming an arterial rete. He

found that it left the lymph forming centers through the posterior

foramen of the cavity and entered the distal part of the penis.

List of terminology:

_p._pudenda communis Du Toit, 1913 Liebe, 1914 Kaupp, 1918

Syn: _Ap hypogastricae Barkow, 1889 Tiedmann from Barkow, 1829 parietal branch Westpfahl, 1961 _A_. profunda penis Liebe, 1914

_A._ppdenda interna Liebe, 1914

Du Toit, 1913 Kaupp,.1918

Syn:' ramus intestinalis Westpfahl, 1961 visceral branch Sapy, 1941 39

_A._pudenda externa Du Toit, 1913

Syn: parietal branch Sapy, 1941 muscular rami Westpfahl, 1961

_A. mesenterica caudalis Sapy, 1941 Westpfahl, 1961

mesenterica inferior Du Toit, 1913 mesenterica_posterior Liebe, 1914

The terms used in this paper to refer to arteries in this area

are:

I. Aorta descendens

A. _M. sacralis media

B. A. mesenterica caudalis

cocpygeus media ('3

Is»

U _ppdenda communis

I.»

H _A_. hemorrhoidales

2. A._pudenda externa

.— 3. A. pudenda interna

Caudalis is used to refer to_A, mesenterica caudalis which seems

to minimize the confusion sometimes associated with superior-inferior

or anterior-posterior and is considered to be a more exact term.

Nerves

Liebe (1914) divided the nerve plexus in the pelvis into three

groups: I. Plexus cruralis syn. lymbar plexus, II. plexus ischiadicus

and III. plexus_pudendus. The plexus cruralis, he stated, does not

supply the cloaca, except for one branch which innervates a portion of

the p. sphincter cloacae. The_plexus_pudendus innervates the p. pubi

40 coccygeus (E: depressor caudae), the pp. iliococcygeus (rp. levator caudae),

the p,_sphincter cloacalis (cloacae), the E: transversus cloacalis

(cloacae , and the skin around the vent.

Du Toit (1913) reported that branches of the 3lst and 32nd spinal nerves join soon after their origin and form the strongest nerve branch of the plexus_ppdendus. This branch, he found, takes somewhat of

a separate course and is accompanied by the p, pudenda externa. He

called the nerve p,_pudenda externa. About the middle of its course in

the abdominal cavity it gives off a thin branch, the p, pudendus internus

which runs caudal to the cloaca and the sex organs.

Hsieh (1951) reported that the cloacal plexus is connected to the pelvic plexus by communicating branches which pierce through or run behind the suspensory muscle of the rectum. The cloacal plexus of right and left sides, he found, were interconnected both above and below the cloaca. He reported the presence of a ganglion which he stated con- stituted the pelvic splanchnic nerve and distributed its fibers to the anus (cloaca), the distal part of the ureter, distal part of the vas deferens, the bursa of Fabricius and the muscles of the cloaca. The ganglion, he added, could be observed histologically with nerve fibers running in various directions. The location of this ganglion was found associated with the p,_pudenda interna.

Liebe (1914) reported that the sympathetic trunk forms a dense plexus near the origin of the p, pudenda communis and passes around the

_p._pudenda communis, ureter and ductus deferens. He indicated that the

p, erigentes originates from the sympathetic trunk and supplies the cloaca. 41

Veins

Neugebauer (1845) described the hypogastric veins as arising from vena cutanea pubica, vena cutanea caudae inferior, vena_pudenda and vena

muscularis caudae inferior. The vena cutanea pubica arose from the skin

area around the tail region. The vena cutanea caudae inferior, he

stated, arose at the posterior part of the tail and ran on the lower

surface of the tail to the vena hypogastrica. The vena_pudenda, he

described as originating in the lateral portion of the cloaca and running along with the ureters and artery until it joins the common

trunk of the vena cutanea caudae inferior and vena cutanea pubica. He

reported that in male birds vena_pudenda flows from the corpus cavernosum

and also from the penis or its rudiments. The fourth branch, the vena muscularis caudae inferior runs from the surface of the lower tail muscles to join the vena hypqgastrica.

Gadow (1891) and Kaupp (1918) are in agreement with Neugebauer

(1845) as to the course of the vena pudenda.

In the duck, Liebe (1914) described the venous drainage of the penis as beginning with the y, pudenda which has its origin on both

sides of sulcus. He then stated that the vessel passes through the center of lymph formation and then through the posterior foramen accomr panying the p, pudenda interna.

Du Toit (1913) stated that the vena pudenda interna joins with

the vena_ppdenda externa to form the vena_pudenda communis which anas-

tomoses with the vena coccygeus. The two vena cocqygeae end on both

sides of the aorta in the arcus_pyppgastricus.

Liebe (1914) reported that in the duck the vena pudenda continues cranially following the course of the ureter absorbing the y, muscularis

caudae inferior which drains the caudal muscles and unites with the pp

cutanea pubica which originates in the region of the coccyx. The vessel

formed by the union of these two vessels is the y, pudenda externa

(Du Toit, 1913).

Liebe (1914) reported that the y, pudenda follows the ureter and finally merges into the arch of the y, hypogastrica. Gadow (1891) stated that the y, pudenda along with the ventral yp caudae muscularis inferior form the caudal trunk of the y, hypogpstrica.

Terminology of veins and their Synonyms

Vena hypogastrica Neugebauer, 1845 Gadow, 1914 Du Toit, 1913 Liebe, 1914 Kaupp, 1918

Venappudenda Neugebauer, 1845

Gadow, 1891 Liebe, 1914 Kaupp, 1918

Syn: (divides into two terms) vena_ppdenda interna & Du Toit, 1913

vena_pudenda communis Knight, 1967

Vena muscularis caudae inferior Neugebauer, 1845 Liebe, 1914

Syn: Ventral vena caudae muscularis Gadow & Selenka, 1891

ramus muscularis caudae Du Toit, 1913 Knight, 1967

Vena cutanea pubica Neugebauer, 1845

Gadow, 1891 Liebe, 1914 43

Syn: vena pudenda externa Du Toit, 1913 Knight, 1967

Vena cutanea caudae inferior Neugebauer, 1845 Gadow & Selenka, 1891 Liebe, 1914 Du Toit, 1913 Knight, 1967

Lymphatics

According to Liebe, the lymph is secreted from the vascular body and flows through the posterior foramina of the surrounding cavities,

the lymph formation cavities, to the inside of the penis. Liebe (1914) did not do any original work on the return of the lymph from the penis but did review the work of Mﬁller (1908) and Eckhard (1876). Liebe

(1914) reported that when injecting material into the reproductive structures, the lymphatic vessels filled as far back as the ureters which support the findings of Eckhard (after Liebe, 1914) and Mﬁller

(after Liebe, 1914). There are two vessels for the discharge of lymph from the pelvis, a longer tract with finer vessels and a shorter tract.

These vessels of the larger tract form at the mesorectum in the plexus cruciatus and ascend from the plexus beside the_p. sacralis media,

finally reaching the ductus thoracius dexter.

Baum (1930) reported that the lymphatics of the pelvis and of

the region of the cloaca unite into three or four very fine lymphatic ducts which enter the pelvis merging into one or two lymphatic ducts.

These lie on the ventral side of the p§_lumbrosacral and empty into the cisterna which drains the cloaca.

Dransfield (1944) described the lymphatics following the common pudendal artery. The main trunk, he found, is sometimes double and 44 formed by the union of branches draining the terminal part of the large intestine. The trunk runs forward on the side of the large intestine and the bursa diverging upward and inwards to join the vessel following the middle sacral artery in common with the vessel of the opposite side.

At its origin, the lymphatic duct is joined by lymphatics from the cloacal wall and bursa and receives a branch from ureters and in the male from the terminal portion of vas deferens. The main lymphatic trunks result from the union of the lymphatic vessels following the middle and common pudendal arteries.

No specific terms have been given by these authors for describing the vessels leading from the cloaca to the large lymphatic ducts. OBJECTIVES

To study the anatomy, both gross and microscopic, of the reproductive structures involved in the dilution and deliverance of semen after it leaves the ejaculatory papillae.

To study the relationship of these structures to the cloaca and surrounding structures.

To support or refute data from authors who have dealt with these structures.

To provide information and illustrations for those who are interested in this aspect of the reproductive process of the male domestic fowl.

45 PROCEDURE

Birds used in this study were from the flock maintained by the

Regional Poultry Research Laboratory of the U. S. Department of Agri-

culture in East Lansing, Michigan. Male White Leghorn chickens a year

of age or older were employed for all anatomical studies. The birds were euthenized by an overdose of Equi-thesin R *.

In the gross dissection of specimens an embalming fluid was

used for fixing the tissue. The embalming fluid was prepared according

to the formula received from the South Carolina School of Medicine. It

preserved the specimens extremely well and left the tissue soft and

pliable for ease of dissection. The odor of the fluid was not offensive.

In studying the histological characteristics of the various

structures related to the cloaca, preliminary spaced serial sections

were taken through the entire cloaca in frontal, sagittal and transverse

planes. The tissues were fixed in Bouin's solution and stained. Hema-

toxylin and eosin (Armed Forces Institute of Pathology, 1960), Margolena

and Dolnick's (1951) technique for staining elastic fibers, collagenic

fibers and keratin and Uhgewitter's technique (1951) for nervous ele-

ments as modified by Dennington (Personal communication) were used.

Serial sections fixed in neutralized formalin were taken through

the three planes and stained with hematoxylin and eosin. The continuity

* Jensen-Salsbury Laboratories.

46 47 of various structures could readily be traced through the tissue. In addition, serial sagittal sections were taken through the reproductive structures to be stained with one of the following stains: hematoxylin and eosin, Gridley's reticulum stain, Mayer's mucicarimine stain (Armed

Forces Institute of Pathology, 1960) and Margolena and Dolnick's (1951) stain. The stains were staggered so that each stain was used on every fourth slide through the series.

In addition, Gallego's iron fuschin (Armed Forces Institute of

Pathology, 1960) stain was used to study mast cells in sections taken through the various reproductive structures. Bodian's Method (Armed

Forces Institute of Pathology, 1960) for the study of nerve fibers and endings was employed to supplement Ungewitter's stain (1951).

Ink injections, employing Gunther wagner Pelikan—Werks ink for— mulated for biological injection (Peterson pp p£., 1965) were made and sections were taken through the various reproductive structures and stained with hematoxylin and eosin. RESULTS

Gross Anatomy

Cloaca

The cloaca is located in the midline of the body, ventral to the base of the tail and dorsal to the projecting ends of the pubic bones.

It is obscured from casual observation by feathers which are collec- tively referred to by poultrymen as the "fluff". This fluff is a come posite of feathers which lie in two feather tracts, the medial abdominal and the latteral abdominal tracts. These tracts can be observed when the feathers have been clipped off at their bases.

The only feather tract which lies entirely on the lips of the cloaca is the cloaca circlet. It is composed of a single row of feathers arranged in a circle. The feathers are very small and lie on the dorsal and ventral lip proper, next to the marginal portion of the lip.

The feather tract lying dorsal and ventral to the cloacal circlet is the medial abdominal feather tract (Fig. 1). This tract can be divided into two segments, one found on the abdomen, cranial to the cloaca, and the other located on the dorsal lip. The latter is sometimes referred to as the cloacal tract, which is a subdivision of the larger abdominal tract. The abdominal portion of this tract is composed of several rows of feathers which begin in the midline at the base of the ventral lip of the cloaca and pass cranially between the projecting

48 49

ends of the pubic bones. The cloacal tract portion consists of l - 3

rows of feathers. Laterally, only one row of feathers is found, but as

the cranio-caudal dimension of the dorsal lip increases there is a cor—

responding increase in the number of rows of feathers. It is the only

other tract besides the cloacal circlet which lies directly on the

cloaca.

The lateral abdominal tract lies lateral to the cloaca and the medial abdominal tract. This tract is found covering the area of the

abdomen dorsal and lateral to the medial abdominal feather tract and

ventral to the caudal apterium.

The ventral caudal apterium (apterium - literally, absence of

feathers) lies dorsal to the lateral abdominal tract and covers the

ventral surface of the tail.

The cloacal apterium is found in the midline on the dorsal lip

of the cloaca and separates the caudal portion of the medial abdominal

tract (cloacal tract) into right and left parts. It extends from the

caudal apterium to the margin of the dorsal lip..

The cloaca externally is composed of two lips, a larger dorsal

lip and a smaller ventral lip (Fig. 1). The ventral lip is an unpaired

structure which crosses the midline dorsal to the protruding ends of

the pubic bones. The ventral lip projects out from the abdominal wall

only a short distance, approximately 3 mm.

The ventral lip can be divided into two parts, the ventral lip

proper and a marginal portion. The ventral lip proper is the area

between the abdominal wall and the edge of the margin which is a dis-

tance of approximately 1 mm. This area is covered with epithelium

which appears like the epithelium of the general body surface. The 50 single row of feathers of the cloacal circlet lies at the base of this area.

The marginal portion of the ventral lip is larger than the rest of the ventral lip. The epithelium of the margin also has a different texture, having a number of ridges and grooves which run dorso-ventral.

The ventral lip is attached to the underlying tissue which makes it a rather rigid structure and it is not easily displaced.

The dorsal lip is considerably larger and more pronounced than the ventral lip. It has its origin immediately ventral to the base of the tail projecting out from the abdominal wall, overhanging the ventral lip. Its dorso-ventral dimension in the midline is approximately 17 mm. from the base of the tail to the margin of the lip. The dorsal lip, in contrast to the ventral lip, is unattached ventrally, overhanging the proctodeal cavity, and can easily be displaced. The dorsal lip acts as a flap or cover over the cloacal opening.

The dorsal lip can also be divided into two parts. The dorsal lip proper is covered with the integument characteristic of the general body surface. The single row of feathers of the cloacal circlet is found on the dorsal lip proper close to the margin. The cloacal tract portion of the abdominal feather tract lies entirely on the dorsal lip.

The cloacal apterium, as mentioned previously, is found on the dorsal lip.

The marginal portion of the lip is similar in external characteristics to that of the ventral lip. However, due to the semicircular shape of the dorsal lip, the ridges and grooves do not run dorso-ventrally as they do on the ventral lip. Laterally and ventrally the grooves begin to change and lie more latero-medial. At the lateral boundary the 51 grooves are running in a definite latero-medial direction. This, in principle, is the same as making a series of perpendicular lines on a

straight surface and then bending the surface in the shape of a semi-

circle (Fig. l).

Proctodeal Fold

The lips of the cloaca appear circular when the dorsal lip is

displaced dorsally (Fig. 2). With the lip in this raised position, the

cloacal opening is revealed. The cloacal opening or vent constitutes

the external orifice of the cloaca and is created by the incomplete

central fusion of the proctodeal fold. The proctodeal fold is a thin

sheet of tissue which originates at the margin of the lips and extends medially forming the posterior boundary of the proctodeal cavity. The

fold does not have the massive characteristic of the lips but appears

as a thin curtain of tissue covering the opening. It is thickest at

its attachment at the lateral margin and tapers medially. The fold is

bilaterally symmetrical, having equal right and left sides. In the

dorsal midline, where the two halves of the fold unite, the fold has

its smallest central extension. The fold, ventrally, becomes progres-

sively wider corresponding to the increase in diameter of the procto— deal cavity and acts as a curtain over the proctodeum. At the junction

of the dorsal lip with the ventral lip, the fold reaches its greatest width.

Just ventral to the junction of the dorsal and ventral lip, the

fold becomes attached to the underlying structures of the proctodeal

cavity. It retains its fold-like appearance externally, even though

attached, until it reaches the ventral margin of the cloaca. In the 52 ventral midline the two sides of the fold join, limiting the ventral extent of the cloacal opening. This union is just ventral to the base of the phallus which is indicated in Fig. 2. There is a slight depression in the ventral midline where the two sides of the folds come to- gather.

The external surface of the fold is smooth in comparison to the more ridge—like margin. The free portion of the fold is flexible in the dead animal but firm in the living bird. This is due to the musculature in the fold.

The fold appears to have two qualities or textures on its surface, one extending from the margin and covering three-fourths of the distance from the margin of the lip to its free edge. At this point, the texture of the fold becomes smoother and appears to be more moist. The difference is slight but apparent.

When the lip is placed in its normal position (Fig. 1), it is observed that the portion attached to the dorsal lip is free and over— lies the attached portion of the ventral lip, the fold actually being folded over on itself (Fig. 5).

Proctodeal Cavity,

The opening in the proctodeal fold also reveals a portion of the proctodeal cavity (Fig. 2). From this restricted view, some of the structures of the proctodeal cavity may be identified. These structures can be used for orientation when the proctodeal fold is drawn laterally, to reveal the contents of the proctodeal cavity (Fig. 3).

The opening of the cloacal bursa lies in the dorsal aspect of the proctodeum. The uroproctodeal fold forms the ventral boundary of the 53 bursal opening. A small portion of the phallus can be observed in the most ventral and caudal portion of the cloacal opening lying directly dorsal to the ventral junction of the right and left portions of the proctodeal fold.

By attaching forceps to the proctodeal fold at points A, B, C,

D, and E, as indicated in Fig. 2 and pulling the fold peripherally, the proctodeal cavity and its contents are revealed (Fig. 3). Most of the structures appear in this illustration in their entirety.

The opening of the cloacal bursa is found mid-dorsally at the junction of the internal surface of the dorsal lip with the uroprocto— deal fold. The opening appears convex in shape. The dorsal boundary of the opening is formed by a layer of tissue which distends from the opening onto the ventral surface of the dorsal lip. This bundle of tissue is conical in shape with its apex at the posterior end of the dorsal lip and its base at the opening of the bursa. Its base is as wide as the opening of the cloacal bursa.

Uroproctodeal Fold

The uroproctodeal fold forms the ventral boundary of the opening of the cloacal bursa, the cranial boundary of the proctodeum and the caudal boundary of the urodeum. It is circular in appearance but can— not be seen in its entirety (Fig. 3) because its ventral portion is obscured from View by the phallus, round bodies and lymph folds. The uroproctodeal fold or second cloacal fold separates the proctodeum from the urodeum. In the live animal it is red in color and glistening moist. In the ventral portion of this fold, is the uroproctodeal opening. In Fig. 3, only the most dorsal portion of this opening can 54

be observed. Fig. 4 reveals the ventral extension of the uroproctodeal

fold. A point to observe is the location of the uroproctodeal opening which lies in the ventral third of the uroproctodeal fold.

In Fig. 4, the ventral attachment of the uroproctodeal fold can be observed at the cranial base of the reproductive structures of the

proctodeum.

Urodeum

Figures 4 and 5 illustrate the structures located in the urodeum.

The ureter lies dorsal to the ejaculatory papilla within the confines of

the urodeum. The ureter is generally difficult to locate in the living

bird but can be distinguished when urine flows periodically from it.

The ejaculatory papillae are readily observed and often they can be

observed emerging through the uroproctodeal opening into the proctodeal

cavity (Fig. 4). The urocoprodeal fold lies cranial to the urodeum

forming the cranial boundary of the coprodeum. The coprodeal opening

leads to the chamber of the coprodeum which is the most cranial of the

three chambers of the cloaca.

Phallus

The phallus is found in the ventral midline of the proctodeal

cavity directly caudal to the uroproctodeal opening and cranio-dorsal

to the ventral junction of the proctodeal fold. The gross morphology

of the phallus is illustrated in figures 2, 3 and 5.

The phallus is a firm, white structure which is located in the midline of the proctodeum. The phallus is dome-shaped and has a smooth

surface which is glistening moist in the live bird. Its approximate 55 dimensions are 2 — 3 mm. medic-lateral, 3 mm. cranio—caudal and 3 mm. dorso-ventral.

Cranial to the phallus lies the uroproctodeal fold. This fold is separated from the phallus by the ventral extension of the proctodeal cavity which ends blindly ventral to the base of the phallus.

The phallus is separated laterally from the adjacent round bodies by a shallow groove; this groove runs in a cranio-caudal direction.

The cranial aspect of the groove lies more medial than the caudal aspect.

Thus, it is set at an oblique angle. The tissue lining this groove is more characteristic of the tissue of the round body and appears as a continuation of the round body to the sides of the phallus.

Caudally, the same type of tissue as that lining the groove is found at the base of the phallus, giving the impression that the phallus is super-imposed on the round bodies.

On the cranial surface of the phallus is found a slight depres— sion running dorso—ventrally. It is found in the midline and is associated only with the phallus. This depression is not to be confused with the groove which is formed by the phallus and the other reproductive structures made for semen delivery. In the stimulated condition, the phallus forms the floor of the channel which conducts semen to the outside. This depression in the phallus would be found on the floor of this channel.

Round Bogy

The round bodies which were mentioned in connection with the phallus are the most medial of the paired reproductive structures of the proctodeum. They are situated between the centrally located phallus 56 and the laterally located lymph folds. They vary in size and shape depending on the age of the bird and the degree of stimulation. They can, however, be considered to have the following approximate dimensions:

3 mm. medio-lateral, 5 mm. cranio—caudal and 2.5 mm. dorso-ventral

(average measurement of 10 males). The latter dimension is usually found to be slightly less than that of the phallus when these struc— tures are not stimulated.

In the quiescent stage, the round bodies appear as folded triangular-shaped structures (Fig. 3). The apex of the triangle is found cranio-caudal to the phallus. The base of the triangle is toward the proctodeal fold. The sides of the triangle are formed by the grooves which separate the phallus and the lymph folds from the round body.

In the stimulated condition the round bodies become distended with fluid imparting to them a more rounded shape. This increase in size causes them to approach each other in the midline and also aids in pushing the phallus down and outward thereby forming the channels through which the semen will flow.

The round bodies can be distinguished visually from the phallus in the living bird by their red color which contrasts with the white of the phallus. They are a more flacid structure in the unstimulated live bird as compared to the more rigid phallus. The glistening, moist character of its surface is similar to that of the phallus.

On the dorsal surface of the round body of one bird examined, small grooves could be found running in a cranio-caudal direction. They were very small, being barely discernible to the unaided eye. 57

The round bodies do not lie on the same horizontal axis as the phallus but lie slightly cranial to it. The medial aspect of the round body is found to be more caudal than the lateral portion.

Lymph Folds

Lateral to the round bodies are the lymph folds. These are paired structures which together with the round bodies and phallus form a ridge of reproductive structures which lie on the ventral surface of

the proctodeum. They lie slightly cranio-lateral to the round body in close association with the lateral wall of the proctodeum. The proctodeal fold covers them caudally and the uroproctodeal fold lies cranial

to them separated by the proctodeal cavity (Fig. 3).

The lymph folds are more or less spindle-shaped structures with

their long axis running in a caudo-medial direction with the cranial

aspect of the fold toward the uroproctodeal opening.

They appear reddish in color similar to that of the round bodies.

The surface of the lymph fold is smooth and moist. The structures are

smaller than either the round bodies or the phallus, and project up

from the floor of the proctodeal cavity.

The round bodies are separated from the lymph folds by a groove which is deeper than the separation between the round bodies and the phallus. Between the lymph fold and the uroproctodeal wall is another groove which is their lateral boundary. The structure is relatively

firm in the quiescent stage. The dorsal surface of the lymph fold is rounded and thrown up into folds. 58

The vascular body, which is the most lateral of the reproductive structures, lies outside the proctodeal cavity. In order to understand its relationship to the reproductive structures of the proctodeum and to the cloaca as a whole, it is first necessary to describe landmarks for orientation before considering the vascular body itself. Thus, the musculature, vascular, and nervous distribution pertinent to the area will be discussed prior to the description of the vascular body.

Musculature

By removing the skin from the cloaca and surrounding area, several muscles are found which have a direct relationship to the re— productive structures of the proctodeum. They are of particular importance in locating the vascular body and even more important in the study of the microscopic characteristics of the reproductive structures.

Figures 6 and 7 are presented to illustrate the various muscles and their relationship to the cloaca and to the vascular body. In

Figure 6, the tail is elevated so that the very tip of it is in the same plane as the lips of the cloaca. The right side appears as one would see the cloacal musculature after the integument has been removed. Some of the fat has been dissected away to permit the observation of the musculature. Some connective tissue has also been removed to reveal the muscles as separate entities; no further dissection was done.

In order to reveal the underlying structures, the left side has been dissected with some muscle displacement. An incision was made at the base of the ventral lip and a thread was attached to the p, sphincter cloacae at the junction of the dorsal and ventral lips and then pulled 59 dorsally. A piece of muscle was removed from the p. transversus cloacae.

Connective tissue and fat in this area were removed and the muscles separated from one another.

The musculature will be discussed beginning with the muscles of the lips and then moving cranially and laterally.

3p sphincter cloacae -- The E: sphincter cloacae is the major

muscle of the dorsal and ventral lips of the cloaca. From its name, it is apparent that it is part of the closing mechanism of the cloacal opening. It is also involved in the support and shape of the lips.

The p, sphincter cloacae is a circular muscle with its fibers for

the most part circularly arranged. It is very large in the dorsal lip.

As the muscle leaves the dorsal midline it tapers rapidly in its cranio- caudal dimension and by the time it reaches its most lateral extent it has become reduced to 5 mm. At this point, it turns and continues medio- ventral. At the ventral midline it reaches its smallest dimension of

3 mm. The thickness of this muscle remains relatively constant on both dorsal and ventral lips, which is about 3 mm. The muscle extends laterally approximately 10 mm. on each side of the midline, having a total width of 20 mm. This will vary with the width of the cloaca.

At the margin of the lip where the proctodeal fold merges into the lip, the muscle becomes greatly reduced imparting a roundness to the margin. However, some of the fibers do continue into the proctodeal fold. Because of the close association here between the integument and the musculature, it becomes virtually impossible to separate the two.

Therefore, it will be considered in more detail in the histological sections concerning the proctodeal fold. 60

pp contractor cloacae —- The p, contractor cloacae originates

from the ends of the pubic bones and a portion of the median raphe. It has a horseshoe-like shape with the open end lying between the pubic bones and the closed end lying cranial to the.pp sphincter cloacae. The

pp sphincter cloacae covers the caudal portion of the M. contractor

cloacae. The muscle appears to be more flared at its origin but as it passes dorsally it becomes more compact.

In Figure 7, the p, contractor cloacae can be seen projecting

out from abdominal wall along with the pp sphincter cloacae. Thus, the

major components of the dorsal lip are formed from these two muscles; whereas, the ventral lip is smaller as it is composed of only the pp sphincter cloacae.

ventrally the p, contractor cloacae assists in the support of the

abdominal wall after leaving its association with the p, sphincter cloacae.

pp transversus cloacae —- The p, transversus cloacae originates

from the dorso—caudal third of the p, semitendinosus. From its origin

it passes in a medic-caudal direction. As it passes lateral to the pp sphincter cloacae a small portion of the muscle leaves its association

with the main bundle and intermingles with the fibers of the p, sphincter cloacae. Care must be exercised when trying to dissect out this portion of the muscle because this small group of fibers is easily missed. The major portion of the muscle continues ventro-medially, crosses thegp. contractor cloacae and inserts on the median raphe and the caudal end

of the pubic bone. Its insertion is caudal to the origin of the p,

contractor cloacae and ventral to the lower lip of the cloaca. 61

pp levator cloacae -- The p, levator cloacae is a narrow muscle which originates on the ventral surface of the tail, beneath the most lateral rectrix, either the seventh or eighth (in the chicken the number of rectrices varies, usually 7 or 8). It lies medial to the p. depressor caudae and inserts in the midline at the base of the phallus. The muscle becomes flatter as it progresses ventrally.

The p, levator cloacae leaving its origin at the base of the rectrix courses ventrally and medially in close association to thegp.

depressor caudae until it crosses the p, depressor coccygis. At this point it leaves its association with the p, depressor caudae and con— tinues to course medio—ventrally. It passes deep to the p, constractor cloacae.

The p, contractor cloacae acts as a pulley for the p, levator cloacae. When the p, levator cloacae encounters the p, contractor cloacae it is forced to pass deep to this muscle coming to lie between the p, contractor cloacae and the cloaca itself. At this point the cloaca is projecting out from the abdominal wall and carries with it the pp levator cloacae. Originally, the p, levator cloacae was oriented in a latero-medial direction. After dipping below the p, contractor cloacae, its course becomes more cranio-caudal oriented. Leaving its association with the p, contractor cloacae, the p. levator cloacae continues beneath the p, sphincter cloacae and inserts at the base of the phallus close to its homologue from the opposite side.

The p, levator cloacae is one of the most important muscles for use in orienting tissue sections. It is always found ventral to the phallus and the other reproductive structures of the proctodeum. It 62 lies dorsal to the vascular body. It should be re—emphasized here that the muscles just described are observed with the tail in a raised position. The bend of this muscle is more pronounced when the tail is de— pressed.

M. depressor caudae -- The _r_n_. depressor caudae, after it leaves

its association with the p, levator cloacae, passes deep to thegp.

transversus cloacae and inserts on the pubic bone posterior to the pp

contractor cloacae. At its origin the muscle is relatively small but

as it passes ventrally, it increases its width becoming almost fan- shaped by the time it reaches the pubic bone.

pp dialator cloacae -- Another muscle of importance is thegp.

dialator cloacae. This muscle is considerably smaller in size and is

located deep to the p, levator cloacae. It originates from the caudal

margin of the pp_ischii and inserts on the lateral side of thegp. sphincter cloacae. It lies deep to p. contractor cloacae and the _Ip.

levator cloacae. It crosses the p, levator cloacae at right angles

when the tail is depressed. The muscle courses around the p. sphincter cloacae where it makes a right angle turn and proceeds down the lateral side of the pp pphincter cloacae. It can easily be differentiated from

the M. levator cloacae by its lighter brown to tan color. However, this

makes it more difficult to separate it from the surrounding connective tissue. Because of its color, size and location, care must be used to isolate this muscle.

pp depressor coccygis -- The largest muscle to be considered is

the p, depressor coccygis which originates on the medial border of the 63 pubic bones and inserts on the ventral surface of the tail. It originates deep to the E: depressor caudae and proceeds deep to the p. levator

cloacae. The right and left muscle bundles join just dorsal to the cloaca, leavinga triangular space. The cloaca forms the base of the triangle and the muscle bundles form the sides. Fat is located in this triangle and deep to the fat is located dense connective tissue.

Ventral to the cloaca and lying between the pubic bones is a dense fibrous connective tissue which usually is overlaid with fat.

This serves as an attachment for the p, transverse cloacae, p, sphincter

cloacae and.pp contractor cloacae and acts as support for the abdominal wall.

Arteries

The aorta of the White Leghorn fowl arises from the left ventricle and continues cranially forming an arch, and then continues caudal as the aorta descendens.

The aorta abdominalis terminates after giving off the two large

_p. ischiadica to the hind extremeties (Fig. 8). The_p. sacralis media

continues in the midline caudally beneath the tail. The vessel is much reduced in size as compared to the larger aorta or_p, ischiadica. The

p, sacralis media gives of paired_p, sacralis lateralis which are branches

which supply the sacral vertebrae and the dorsal musculature.

A short distance from its origin the p, sacralis media gives off

the large unpaired p, mesenterica caudalis. This vessel divides shortly

after its origin into two branches, one passes cranially to supply the ceca and large intestine and the other branch goes caudally to supply 64

the rectum and the cranial portion of the cloaca. The cranial portion

forms an anastomosis with the p, pudenda interna.

The p, pudenda communis are paired vessels which branch from the

_p. sacralis media just caudal to the origin of the p, mesenterica

caudalis. This pair of vessels in two specimens arose at the level of

the p, mesenterica caudalis. On another specimen, one originated cranial

to the other. Generally, both arise caudal to the p, mesenterica

caudalis but close to it.

The_p. sacralis media after giving off the_p. pudenda communis

continues caudally as the_p, coccygea media. Its branches are dis-

tributed to over-lying vertebrae and dorsal musculature.

The pair of_p. pudenda communis arise from the p, sacralis media

in the shape of an inverted Y. The pp, pudenda communis form the two

legs and the p, sacralis media the stem. The origin of the p, pudenda

communis is at the level of the terminal portion of the caudal lobe of

the kidney. From this point, they continue caudo—laterally and slightly

ventrally on each side of the abdomen. As they course laterally they

encounter several structures which run in a cranio—caudal direction.

These are the ductus deferens, ureter, p, pudenda and y, hypogastrica.

The p, pudenda communis parallels these structures for a short

distance and then divides into the p,_ppdenda interns and externa. The 33 pudenda externa leaves the association of the four struc-

tures previously described and continues on the side of the abdominal

wall. It supplies the dorsal lip of the cloaca and the muscles of the

tail.

The p,_ppdenda interna is the vessel which is of primary concern

as it supplies the reproductive structures in the cock. After arising 65 from the p,_pudenda communis, it continues directly caudad with the ureter, ductus deferens, p, pudenda and p, pudenda.

These structures lie in a bundle surrounded by connective tissue.

In Figure 8, the structures have been separated to illustrate them as separate entities.

The p, pudenda interna lies medio—ventral to other structures

through most of its length. However, just anterior to the cloaca there is a shift in relationship. The 33 ppdenda interna continues past the level of the urodeum while the ureter and ductus deferens terminate there. The p,_pudenda interna passes dorsal and lateral to the ureter and to the ductus deferens at the level of the coprodeum and then con— tinues its course caudad. The vessel follows the curvature of the caudal end of the abdominal cavity which courses medially. The artery lies in the connective tissue which is found between the cloaca and the abdominal wall.

Just before crossing the ureter and ductus deferens it gives off two branches which supply the rectum and coprodeum. After emerging from beneath the ductus deferens and the ureter the vessel crosses medial to the p, levator cloacae. After crossing this muscle, it en-

counters the vascular body. Here it bifurcates almost immediately sending one branch across the dorso-medial surface of the vascular body and the other across the ventral medial surface. The dorso-medial branch continues across the vascular body giving off branches to the vascular body. After it has coursed the longitudinal axis of the vascular body it is much reduced and continues on to supply the phallus and other reproductive structures of the proctodeum. The ventro-medial 66 branch also becomes greatly reduced after coursing across the vascular body. It continues on to supply the abdominal wall just below the cloaca.

Veins

The venous system closely follows the course of the_p. pudenda communis and its branches (Fig. 8). The y, pudenda interna drains the

tissue of the reproductive structures and the ventral portion of the proctodeum. As it courses cranially, it parallels the_p, pudenda interna,

crossing the vascular body from which it receives two or three branches.

As it courses toward the cranial end of the vascular body it crosses the ventral branch of p, pudenda interna coming to lie on the medial side

of this vessel. At the cranial border of the vascular body, it joins the muscular branch of the y, pudenda interna. It then crosses dorsal

to the ductus deferens and the ureter coursing cranially with the p: pudenda interna until it is joined by the y, pudenda externa. At this

point, they form the y, pudenda communis which empties into the y,

hypogastrica. This vessel passes into the kidney. The vessel emerges from the kidney at the medial lobe and proceeds dorsally until it joins the y, cruralis. At this junction, the large y, iliacus communis is

formed which joins with the opposite side in the midline to form the y, cava_posterior.

vascular Body

The vascular bodies are paired reproductive structures which lie outside the confines of the proctodeal cavity (Fig. 6). They are structures closely related to the proctodeum being connected by way of 67

channels to the other reproductive structures of the proctodeum. They appear as bean-shaped structures, having a distinctive red quality which

is imparted to them by the many capillaries found within the organ.

The vascular bodies can be located on the surface of the body by drawing a perpendicular line from the ends of the pubic bones up to the base of the vental lip (this line should pass close to the junction of dorsal and ventral lips). A perpendicular line drawn about 2 mm. from

the midline is the most medial boundary of the vascular body. A line

following the course of the cloacal circlet on the ventral lip between

these two lines will provide an approximate guide for finding the vascu-

lar body. Because of the projection of the dorsal lip, the vascular body does not lie on a horizontal course, but rather in a cranio-caudal direction. Therefore, its horizontal axis will not parallel the course of cloacal circlet exactly.

The caudal portion of the cloaca fuses with the abdominal wall.

In this area, between the cloacal wall and the abdominal wall is con— nective tissue which binds the two walls together and contains the vascular body. Figures 6, 9 and 10 reveal this relationship. It is

this connective tissue area between the walls of the cloacal chambers

and the abdominal wall which becomes of major importance in the study of

the reproductive structures. The reproductive structures are found to be intimately associated with this connective tissue. The phallus, round body and lymph fold appear as dorsal projections of this con— nective tissue into the lumen of the proctodeum.

The lateral aspect of the vascular body lies between the coprodeal wall and the abdominal wall (Fig. 8). Moving medially, the vascular body lies ventral to the urodeum and proctodeum. Since the proctodeal 68 wall projects out from the abdominal wall, the vascular body is also found to lie out from the wall. The long axis is oblique with the caudal portion being more medial than the cranial portion.

In Figure 9, the vascular body is found to lie deep to the p, transversus cloacae and the p, sphincter cloacae. The p, transversus

cloacae overlies a greater portion of the vascular body. Thegp. sphincter cloacae overlies the more medial aspect of the body and the

larger channels which are coursing to the reproductive structures. As can be observed in the parasagittal section (Fig. 9), the p, transversus cloacae undercuts the p, sphincter cloacae to cover the vascular body.

This section is taken from the extreme left side of the cloacae so that only a very small portion of the proctodeum is observed. Because of the ballooning nature of the coprodeum, its lumen can be observed. The urodeum is not seen due to its small size.

The pp. levator cloacae crosses the dorsal surface of the vascular

body. The p. dilator cloacae forms an "x" with the p, levator cloacae

and coincides with the cranial boundary for the vascular body. The medial boundaries of the vascular body is formed by the various chambers of the cloaca.

In order to locate the vascular body, it is necessary to first remove the skin covering the area, except where the skin becomes closely affixed to the margin of the cloaca. In some birds, particularly older, well-fed males, a large amount of fat will be found beneath the skin.

Particularly abundant fat areas are located just dorsal to the cloaca between the p, lateralis coccygeus and overlying the sheath of the p,

rectus abdominus. Removal of the fat will reveal the muscles shown in

Figures 6 and 7. After removal of the fat, the.pp transversus cloacae 69 has to be separated and bisected. The ventral portion of thegp. contractor cloacae is found below the p, transversus cloacae and has

to be incised horizontally just above its origin. The muscle is then dissected from the underlying tissue.

Elevation of the p, transversus cloacae exposes the vascular

body in a bed of connective tissue. It is easily differentiated from the surrounding tissue by its bright red color. The vascular body is found to extend to within 2 mm. of the midline. About 4 mm. therefore separate the right and left vascular bodies.

The lateral aspect of the vascular body lies directly ventral to the ductus deferens. The ductus deferens, in turn, lies directly below the ureter (Fig. 8). The ductus deferens and the ureter empty into the urodeum at this level and the vascular body comes to lie ventral to the urodeum. At this level it leaves its association with

the p, transversus cloacae and is found lying cranial to the connective

tissue raphe. From this point on, channels leave the vascular body and course to the reproductive structures in the proctodeum. The channels are covered caudally by the p, sphincter cloacae and cannot be observed

by the unaided eye (Fig. 14). HISTOLOGY

Dorsal Lip

The dorsal lip of the cloaca is covered on its external surface

by tissue characteristic of the general body surface; whereas, the

lining on the internal surface or proctodeal surface is characteristic

of the lower digestive tract. The epidermis of the dorsal lip is com-

posed of two layers, an outer stratum corneum and a deeper stratum

‘germinativum. The stratum corneum is a layer derived from living cells

which have died forming this layer. It varies in thickness depending

on the degree of cornification and the amount of sloughing which has

occurred.

Beneath the stratum corneum lies the stratum germinativum which

can be divided into three subgroups (Lucas, personal communication), a

stratum basale, stratum intermedium and stratum transitionale. The

stratum basale is located on a basement membrane and is composed of a

single layer of cells which contain large circular to egg-shaped nuclei.

Above the stratum basale lies the stratum intermedium which is composed

of a layer of cells whose nuclei appear more rounded than those of the

stratum basale. These cells have more cytoplasm surrounding their

nuclei than the cells of the more packed stratum basale. The stratum

intermedium is composed of l - 3 layers of cells on the dorsal lip.

Above the stratum intermedium lies the stratum transitionale which is

7O 71

composed of l - 3 layers of flattened cells with corresponding flattened nuclei. Usually present in these cells are many vacuoles. Above the

stratum transitionale lies the stratum corneum.

The basement membrane which separates the epidermis from the

dermis is not easily detected unless stained with special stains.

The dermis is subdivided into three layers, a stratum super-

ficiale, a stratum_profundum and a stratum lamina elastica (Lucas, per—

sonal communication). The stratum superficiale lies immediately below

the basement membrane of the epidermis composing about one—third of the

total dermal layer. The connective tissue is loosely arranged and

contains elastic fibers which are scattered throughout the layer. These

elastic fibers remain as individual fibers rather than combining to

form bundles of elastic tissue. The most prominent feature of this

particular layer is the presence of many blood capillaries which are

found throughout the tissue. At the bottom of this layer are larger vessels supplying these capillaries.

Below the stratum superficiale is the stratum profundum. This

layer composes about two-thirds of the dermis and can be divided into

two substrate, stratum compactum and the stratum laxum. This division

is based upon the arrangement of connective tissue elements present.

The stratum compactum lies above the stratum laxum and is com-

posed of a dense fibrous type of connective tissue which is irregularly

arranged. It composes two-thirds of the stratum profundum. The stratum

laxum is composed of loosely arranged connective tissue containing

rather large blood vessels and nerves.

In some areas, lymphoid tissue is found in the stratum compactum

and occupies a space between the stratum superficiale and the stratum

laxum. 72

The smooth dermal muscles of the abdominal feather tract and the

cloacal circlet are found in the dermis. There is normally present an

elastic layer below the level of the dermal muscles which is called the

stratum lamina elastica. This elastic membrane was not apparent to en-

able a clear differentiation between the dermis and the subcutis. The

reason the membrane could not be conclusively determined was due to the

presence of many elastic elements in this area which are normally present

in addition to the stratum lamina elastica. However, the stratum lamina

elastica is usually considered to lie at a level just below the dermal

muscles and this is the principle used here to separate the dermis from

the subcutis.

The subcutis is composed generally of loose connective tissue.

0n the dorsal lip, however, it is composed first of a dense type of

connective tissue and occupies a space between the dermis and the muscu-

lature. This connective tissue then becomes loosely arranged as it

nears the muscle bundles. Close to the muscle bundles the subcutis

contains blood vessels and nervous elements. Elastic fibers are present

in considerable quantity in the subcutis and they extend up into the

dermis. Many aggregations of elastic fibers are found in both layers.

Below the subcutis lies the epimycium of the muscle bundles com-

posing the p, sphincter cloacae. These muscle bundles are arranged into

an outer circular and inner longitudinal layer. Grossly, however, they

cannot be separated. The muscle bundles are divided by connective

tissue of the perimycium which contains many elastic fibers. Arteries,

veins and nerves are also found in the perimycium. The connective

'tissue forms the epimysium on the proctodeal side of the muscle bundles

which has the same characteristics as the epimycium on the side next to 73

the external body surface. The p, sphincter cloaca is the dividing

structure between the integument and structures of the digestive tract.

Therefore, deep to the M. sphincter cloacae, the dorsal lip assumes the characteristics of the digestive tract, having a mucosa and submucosa.

The submucosa lies deep to the epimycium.of the p. sphincter cloacae.

It contains large blood vessels and nerves, dense connective tissue and considerable quantities of elastic tissue nets which seem to increase

as they approach the lamina ppopria of the mucosa. The lamina propria

and the lamina epithelialis comprise the mucosa. The lamina_propria

is between the lamina epithelialis and the submucosa and contains

eosinophils, plasma cells, lymphocytes, some glands and aggregations of lymph tissue. The glands present are simple branched acinous type

and are very numerous. Elastic tissue of the submucosa is found lying

around the base of many of these glands.

The glands are composed of simple columnar epithelium with goblet

cells. Ducts leading to the proctodeal surface are also lined with

columnar epithelium and contain goblet cells.

Ventral Lip

The ventral lip of the cloaca appears similar in structure to

the dorsal lip. It has a stratum corneum and germinativum similar in

size and structure to that of the dorsal lip. The dermis is also very

similar to that of the dorsal lip. Deep to the dermis lies the subcutis

followed by the M. _sphincter cloacae. It is deep to the p. sphincter

cloacae that a major change in tissue structure is found. Many intervening structures are present between the p, sphincter cloacae and the

submucosa of the proctodeum which are not found in the dorsal lip. 74

In order to complete the external characteristics of the cloaca,

the proctodeal fold will be discussed before considering the constituents deep to the E- sphincter cloacae of the ventral lip.

Proctodeal Fold

The proctodeal fold being a continuation of the dorsal and ventral

lips over the opening of the proctodeum is found to possess most of the histological features of the lips. The major difference in size is due

to the decrease in the tissue components found in each layer.

The epidermis of the external surface of the proctodeal fold may be a thin or entirely absent stratum corneum. There appears to be a

steady decregse in the amount of cornified tissue from the margin of the

lips to the free edge of the fold. In contrast, the stratum germinativum

increases in thickness markedly. The stratum basale is composed of 3 -

4 cell layers, the stratum intermedium is found to be 4 - 5 cells thick

and the stratum transitionale contains 5 - 7 cell layers. This is in

contrast to the epidermis of the lips which contains 1 - 2 cell layers

in the stratum basale, l - 3 cell layers in the stratum intermedium and

l - 3 cell layers in the stratum transitionale.

Below the stratum basale the basement membrane was not observable

due to the numerous elastic fibers found in the dermis. The dermis in

the proctodeal fold is difficult to separate from the subcutis which, in

turn, is difficult to separate from epimycium of the p, sphincter cloacae.

The dermis is markedly reduced in comparison to the dermis of the lips.

The stratum compactum is present but reduced. A stratum superficiale

is found next to the stratum basale containing, generally, few small vessels. The stratum laxum is a thin layer. The stratum lamina elastica

75 was not visibly present but as was discussed in the description of the

lips of the cloaca the elastic tissue of the subcutis obliterates its

identification. Aggregations of lymphocytes can be found in the dermis.

The p, sphincter cloacae continues into the proctodeal fold but

is greatly reduced in thickness. Near the free edge of the fold most of

the muscle fibers are longitudinally arranged; whereas, the circular musculature tends to gain prominence as it approaches the attachment of

the fold to the margin of the lips. Parasagittal sections made lateral

to the proctodeal opening reveals that the p, sphincter cloacae runs up

into the proctodeal fold uniting the musculature of the dorsal lip with

that of the ventral lip. Elastic tissue fibers are found in the epimysium

and perimysium and they extend into the subcutical and dermal layers. The pa. _sphincter cloacae lies in close association with the epidermis of the

external surface, being separated by the relatively small dermal sub-

cutical and perimycial layers. The width of these three layers is

approximately equal to the width of the overlying epidermis.

The internal surface of the proctodeal fold differs in character

from the external surface of the fold with the-change becoming apparent

at the free edge of the fold. This change becomes more apparent towards

the margin of the lips. At the free edge, the p, sphincter cloacae is

found to lie deep to a larger dermis than is found between the p,

sphincter cloacae and the epidermis on the internal surface. The size

of the dermis steadily increases on the external surface from the free

edge of the fold to its attachment at the margin. The dermal area at

the free edge is found to contain numerous vater-Pacini corpuscles which

are easily distinguished by their laminated capsule and central axon. 76

Leading away from the free edge to the margin of the dorsal lip,

there is a change in the epithelial character. The change is from a stratified squamous to a simple columnar type eithelium which contains goblet cells. This transformation is well defined and occurs near the attachment of the fold to the lips.

The ventral portion of the proctodeal fold lying caudal to the phallus and round bodies does not undergo this change. The stratified squamous epithelium continues from the free edge to its attachment at

the margin of the ventral lip.

The dermis on the internal surface of the proctodeal fold is

thicker than the dermis on the external surface of the fold. The various strata are readily definable and composed of the same layers as described for the margin of the lips of the cloaca. On the internal surface of

the proctodeal fold, the dermal layers have the greatest increase in size in the stratum superficiale which lies deep to the epidermis. The

connective tissue of this layer is loosely arranged and contains numerous blood capillaries. The larger vessels which supply them can be found at

the base of this layer in the stratum profundum. The stratum profundum

which also increases is composed of more loosely arranged connective tissue fibers than the stratum superficiale. The line between a stratum

compactum and stratum laxum of this layer is not readily apparent. The

stratum elastica and the subcutis is also difficult to differentiate

from the stratum profundum.

The dermis of the proctodeal fold attaching to the dorsal lip contains many more elastic tissue elements than found in that portion of the fold attaching to the ventral lip. The dermis also does not appear to be as thick. As the dermis approaches the margin of the dorsal 77

lip, it assumes the characteristics on the inner surface of the dorsal

lip, being composed of a muscosa and submucosa, the latter contains many

submucosal glands.

ArteriesL_Veinsp Nerves and Muscles Related to the vascular Body

The p, interna_pudenda, y: interna pudenda and the p: pudenda

form a triad and approach the vascular body as a unit (Fig. 8). This neuro-vascular triad lies ventral to the ductus deferens in sections

taken lateral to the vascular body. At this level, the p. levator cloacae lies caudal to these structures. Sometimes all four of these

structures lie in the connective tissue between the abdominal and coprodeal walls. The_p, pudenda lies ventral to the ductus deferens,

the p, pudenda interna lies ventral to the p, pudenda and cranial to

the vein. The y, pudenda interna lies caudal to the artery and cranial

to the p, levator cloacae. The artery is readily differentiated from

the vein because of its location, its very thick wall and its smaller

lumen. The vein in contrast has a very thin wall, and a large lumen generally containing many blood cells.

The_p, pudenda courses to the cloacal ganglion which lies dorsal

to the other structures of the triad. The cloacal ganglion is seen to

contain many unipolar cells which are large and readily identifiable with hemotoxylin and eosin stain. The cells contain large nuclei and

throughout the cytoplasm Nissel bodies are found.

Progressing medially, there is a shift in position of the triad

in relation to the p, levator cloacae. The muscle occupies a more dorsal

position as it approaches the vascular body and at the level of the 78 vascular body, the pp. levator cloacae is located directly dorsal to the

vascular body. The vascular body lies caudal to the triad, thus assuming the former relationship of the p, levator cloacae to the triad, with the muscle now occupying a dorsal and caudal position in relation to the triad.

The p, pudenda interna lies on the medial side of the vascular body (Fig. 8). As it courses across the body, it gives off several large branches into the parenchyma of the tissue. The p, pudenda interna following a similar course to that of the artery is found draining the vascular body. As the p, pudenda interna courses towards

the midline, it is found to lie outside of the tissue of the vascular body. Some of its branches, however, become completely surrounded by the vascular tissue but they ultimately leave the vascular body and supply the abdominal wall. (As was stated in the gross study, the pp and y, interna_pudenda also supply and drain the reproductive structures

in the proctodeum). The p, pudenda interna branches into the vascular

body before the y,_pudenda interna receives its first branch from the

vascular body. The artery passes ventral to the vein to reach the vascular body.

The p, pudenda courses caudo-medially with the other two structures of the neuro-vascular triad. A small ganglion is found just be— fore the vascular body is reached. The larger p, pudenda continues caudally occupying the dorsal portion of the triad. Another ganglion occurs at a level near the medial aspect of the vascular body. The largest size obtained by the ganglion is at a level just before the lymph fold is encountered dorsally in the proctodeum. Medial to this, the nerves leave the ganglion to supply the various structures of the cloaca. 79

No nervous elements were seen passing into the vascular body.

Some were associated with the larger vessels, however. No end organs were found in the parenchyma of the vascular body. vascular Body

With hematoxylin and eosin, the vascular body appears to be come posed of compact bundles of blue staining tissue. The tissue is separated by collecting ducts which are found coursing through the tissue (Figs. 9, 11). At first glance, under low power, it may be thought that this is a lymphoid tissue. Upon closer examination, however, the vascular body is found to contain few lymphocytes. What imparts the blue staining quality to the tissue is the endothelial cells of the capillary walls and the reticular cells. Another characteristic of this tissue is the large number of blood cells found throughout the tissue. These cells are not found in the lymph sinuses but are con— tained within capillary walls.

The tissue, therefore, can be considered as a bundle of capil— laries supplied by the p,_pudenda interns and drained by the y, pudenda

interna. As the branches of the p,_ppdenda interna penetrate into the dense tissue of the vascular body, they are found to subdivide almost immediately into capillaries (Fig. 11). The capillaries have a very tortuous course. The blood passes through the tissue, coming close to the channels. The channels drain away from the capillaries to a large collecting channel. The origin of these channels is very difficult to observe unless very thin sections are made.

The stroma of the tissue is composed of reticular cells and fibers (Fig. 12). The reticular cells contain large nuclei and are 80

usually stellate-shaped, depending on the angle of cut. Employing

Gridley's reticular stain (1960), the many reticular fibers are readily

stained appearing black in color. These compose the supportive tissue

of the vascular body. Margolena and Dolnick's (1951) connective tissue

stain reveals that there are some elastic tissue elements in the tissue

but these are generally associated with the larger blood vessels. Mucin

stain was employed to see if any of the cells secreted mucin. The re—

sults were negative.

The channels which drain the vascular body are lined with endo-

thelial cells. Between the channels lie reticular cells and fibers.

The capillaries are found generally passing next to the reticular cells.

These capillaries with their endothelial cell linings contain red blood

cells which provide a means of differentiating the blood capillaries

from the lymph channels.

_pymph Channels

It is possible to follow the lymph channels from the vascular

body to the reproductive organs cranial to the proctodeal fold by means

of injecting a carbon suspension into the vascular body. Combining

sections of the ink injected specimens with sections made in the transverse, frontal and sagittal planes, a three dimensional view of the dis-

tribution of the vascular channels is obtained. Figure 14 is a composite

of these planes which illustrates the course of the channels to the

reproductive structures in the proctodeum.

In the transverse plane, the terminal end of the vascular body

is revealed lying lateral to the muscularis mucosa of the proctodeum.

Ventral to the vascular body lies the proctodeum. The importantpp. 81 levator cloacae lies dorsal to the vascular body which is used, as was

pointed out in the gross description of the muscle, as the landmark for orientation of histological sections in this area. It will lie dorsal to the vascular body in sagittal and transverse sections.

The channels course dorsally, coursing medial to the p, levator cloacae (Fig. 14). The p, levator cloacae lies between the channels and the external body surface. The muscle can be observed in a frontal section to insert in the midline to a connective tissue raphe just ventral to the base of the phallus. In this same plane, the fibers are observed to be running horizontal with the plane of cut.

In mammals the diluting fluids are added directly to the pelvic urethra. The channels in their course dorsally were not found to connect with the ejaculatory papilla or the ductus deferens. The diluting fluid must be added after the sperm has left the ejaculatory duct.

Figure 9 reveals the close proximity of the vascular body and the ejaculatory duct with connective tissue forming a separation between them.

Figure 10 is a frontal section through the proctodeum which cuts through the reproductive structures of the proctodeum just dorsal to the p, levator cloacae. It illustrates the course of the channels

through the base of the reproductive structures of the proctodeum just dorsal to the p, levator cloacae. The three dimensional drawing,

Fig. 14, is a more ventral section than Figure 10. The channels are found to lie in the more cranial aspect of the reproductive structures at this level when in the unstimulated condition. The more caudal aspect is seen to be composed mainly of connective tissue elements with many blood vessels interspersed within the tissue. 82

The channels, therefore are found leaving the vascular body, passing dorsally and cranial into the base of the reproductive structures of the proctodeum (Fig. 14). As they pass dorsal to the reproductive structures, they come to occupy a more central position. Figure

13, a sagittal section of the phallus, reveals the more central loca— tion of the channels.

The channels arising from the vascular bodies encounter no

.-WTHI

" observable barriers throughout their course. They are found coursing dorsal into the reproductive structures of the proctodeum. The large channels of the right and left sides are confluent with one another and are located at the base of these reproductive structures sending smaller channels dorsally into the phallus, round body and lymph fold. Thus,

the vascular body is found to be connected with the reproductive struc-

ture of the proctodeum by way of the lymph channels.

Now that the continuity of these structures has been established, a more detailed description of the individual reproductive structures in the proctodeum will be discussed.

Phallus

The phallus, being located in the midline, appears as a dome— shaped structure when cut sagittally (Fig. 13). The proctodeal fold attaches at the base of the phallus to the ventral lip below. There- fore, in a mid—sagittal section, no vestibule is found between the proctodeal fold and the phallus. Usually, however, there is a slight depression between the phallus and the attachment of the proctodeal fold which indicates the ventral limit of the phallus. 83

Parasagittal sections of the phallus pass through the free edge

of the proctodeal fold. The proctodeal fold increases in size as the

sections are taken more laterally. In studying parasagittal sections,

the larger the size of the fold, the more lateral the section. There-

fore, the fold is absent in a mud-sagittal section through the phallus,

a portion of the fold is present when cutting through the round body,

and an even larger portion of the fold is found when sections are taken

through the lymph fold.

The phallus, because of its close proximity to the external

surface, histologically is covered with stratified squamous epithelium which is just a dorsal continuation of the stratified squamous epithe-

lium of the attached portion of the proctodeal fold.

The phallus is generally the easiest structure to observe when

considering the reproductive structures of the proctodeum. It is easily located in sections by the absence of both the proctodeal fold and the p, levator cloacae. A mid-sagittal section, therefore, will

cut through the phallus and this raphe to which the p, levator cloacae

attaches. However, this area is relatively small and a parasagittal cut will generally cut through the phallus and part of the terminal end of the p. levator cloacae. A frontal section through this area reveals

the extent of the;p, levator cloacae and its relation to the base of

the phallus. Under low magnification (10 X) three distinct areas of the phallus can be distinguished, an epidermis, dermis and a large core of connective tissue.

The epidermis consists of a very thin to absent stratum corneum

and a stratum germinativum which lies on both the cranial and caudal

surface. The stratum germinativum on the caudal surface of the phallus

84 has three subdivisions. The outermost layer, the stratum transitionale

consists of 2 — 3 layers of flattened cells with corresponding flattened nuclei. The stratum intermedium is composed of 2 - 3 cell layers with

rounded nuclei. The stratum basale consists of 2 - 3 cell layers closely

packed with round to egg-shaped nuclei. From the caudal base of the phallus to the apex, the epidermis follows a course which is relatively smooth and approximately the same in thickness. 0n the cranial surface of the phallus, the epidermis begins to thicken and has a tendency to be thrown up into the papillary folds. This thickening and papillary fold formation increases progressively from the apex to the base of the phallus. The greatest increase in cell number is found in the stratum intermedium. At the base of the phallus, the stratum intermedium.is

composed of 5 or 6 layers of cells. The stratum basale also increases

in the number of layers of cells having 3 or 4 cell layers. In some sections a corresponding increase of l - 2 cell layers in the stratum transitionale can be found.

In a mid-sagittal section, the epithelium of the phallus changes on its cranial surface from a stratified squamous epithelium to a columnar epithelium which contains goblet cells characteristic of the proctodeal cavity. However, a parasagittal cut will not reveal this transition as the round bodies lie cranial to the phallus and the stratified squamous epithelium continues from the phallus over the round bodies (Figs. 5 and 14).

The dermis of the phallus is composed of a dense irregularly arranged fibrous type of connective tissue. The dermis is thickest on the caudal surface of the phallus getting thinner towards the apex and continues to diminish as it progresses down the cranial surface. In 85 the dermis, small blood vessels can be observed. Deep to the dermis lies a connective tissue core which contains corpuscles of vater-Pacinni.

They are laminated, usually elliptical shaped structures, which are generally quite large. Their central axon surrounded by an inner bulb is readily seen. Outside the inner bulb is an outer bulb of connective tissue. These nerve end organs have been found in deep connective tissue of the penis, clitoris and urethra of mammals and their position and fonm suggest the possibility that they are stimulated by deep or heavy pressure (Baily, p. 1953). Their presence in the phallus could indicate that they have a similar function in the chicken. Most of the corpuscles of vater—Pacini are found caudal to the base of the phallus with few being found near the apex. In some instances they are found extending to the dermis.

ventral and caudal to the phallus lies the;p, sphincter cloacae;

the muscularis mucosa of the proctodeum lies cranially. Between the

phallus and this musculature lies an area which corresponds to the level of the margin of the ventral lip on the external surface. In this area lie large channels, considerable nervous tissue and rather large blood vessels. There is more dense connective tissue in this area, with little of the looser type characteristic of the phallus. However, some adipose tissue has also been found in this area.

The phallus, when cut in a frontal plane at its base, reveals that a connective tissue core lies in the caudal aspect of the organ.

The p, levator cloacae can be seen approaching this connective tissue

core and is inserted into it as previously mentioned. The connective tissue extends cranially into the phallus while the channels are found lying cranial to the p, levator caudae, forming a semicircle around the

86 core of the connective tissue. These channels lie to the right, left and cranial to this connective tissue core at the base of the phallus.

The connective tissue core located at the base is found to contain many elastic tissue elements which, like the channels, have a semi-circular arrangement. These lie in the core of connective tissue in close proximity to the channels. Elastic tissue elements are also present within the core and within the dermis but they appear to be individual fibers rather than the aggregates found in the outer edge of the connective tissue core. Cutting the phallus parasagitally or transversely does not adequately reveal the relationship of these fibers but only indicates that they are present.

At this level, (Fig. 10) the core is found to be composed mainly of dense connective tissue elements with numerous blood vessels, some nerves and vater-Pacini corpuscles.

The central part of the phallus appears to be composed of a looser type of connective tissue as compared to that of the dermis.

When stained with hematoxylin and eosin, the connective tissue had a lighter color in the core-than it did in the dermis (Fig. 13). The connective tissue elements near the blood vessels within the core appeared to stain darker. Thus the connective tissue present below the dermis appears to be composed mainly of loose areolar connective tissue with elastic tissue elements. There does not appear to be any fat in the structure itself, but some was found at its base.

The channels appear as large endothelial lined spaces which are very prominent throughout the tissue. They seem to pass dorsal to the pp levator cloacae as they enter the phallus. They occupy a more central

87 position within the projecting portion of the structure rather than maintaining the semi-circular pattern described for the base of the phallus.

Round Body

The round bodies are first encountered when sectioning the proctodeum in a sagittal plane at the cranial base of the phallus. As was stated in the gross aspect of this study, the round bodies pass cranial and medial to the phallus. Therefore, the medial portion of the round bodies are cut in lateral sections of the phallus.

The round bodies were observed to originate slightly lateral to the midline appearing as a small projection on the ventro-cranial surface of the phallus. They are covered with stratified squamous epithelium which is a continuation of the stratified squamous epithelium of the phallus. The separation between the phallus and the round bodies at first is just a slight depression which is lined with the stratified squamous epithelium. The stratified squamous epithelium changes to a columnar type epithelium on the cranial surface of the round bodies.

This columnar epithelium continues ventrally to the floor of the proctodeum and then turns dorsally and lines the uroproctodeal fold. At the level or slightly ventral to this level where the stratified squamous epithelium changes to columnar epithelium, the muscularis mucosa is

found. This smooth muscle is composed of inner longitudinal and outer circular muscle bundles. The muscularis mucosa was not found pene-

trating into the round body or phallus.

The stratified squamous epithelium of the round body was found to have a more uneven course than the phallus on its inner layers, 88 forming with the dermis papillary folds. The outer surface of the epithelium is smooth appearing; similar to the smooth surface of the phallus. The columnar epithelium close to the midline appears to occupy most of the entire cranial surface of the round bodies but pro— gressing more laterally the columnar epithelium appears to occupy a more ventral position on this surface.

The dermis of the round body is similar to that of the phallus.

It is difficult to differentiate the area of the dermis from the con— nective tissue which is found within the round body as both appear to be composed of dense connective tissue. The looser connective tissue of the phallus is not apparent in the round body.

The channels, in sections taken through the round body just lateral to the midline, appear to have a few branches passing into the round body but the majority pass into the phallus. The more lateral the section, the more channels pass into the round body. At one point the channels were observed to pass into the phallus and round body in equal portions. The appearance in a sagittal section of the channel system is that the large channels lie at the base of the reproductive structures and smaller channels pass dorsally into the phallus, round bodies and lymph fold. This was apparent in several sections having large sinus-like spaces with smaller channels leading off from them.

The channels are endothelial lines. The sinuSelike spaces also appear to be lined with endothelial cells.

_pymph Folds

The medial portion of the lymph folds originate cranial to the round bodies in parasagittal sections. The lymph folds increase in 89 their dorsoventral dimension as parasagittal sections are taken more lateral to the midline. The round bodies correspondingly decrease in size.

Sections of the lymph folds taken from the medial aspect of the structure appear as a small cranial elevation of the round body being separated by only a small indentation between the two structures. Moving laterally the groove deepens with smaller secondary grooves lying on the surface of the lymph folds. These secondary grooves descend into the tissues to varying degrees. None of the secondary grooves, however, are as deep as the groove which separates the lymph folds from the round bodies. Due to these secondary grooves the surface of the lymph folds does not have as smooth and rounded a surface as the round body or phallus and appears to have a rippled surface.

The lymph folds are separated from the uroproctodeal fold by the presence of another deep groove which histologically is readily observable between the two structures.

The lymph folds like the other reproductive structures, are found to have a core of connective tissue containing the channels which originate from the vascular body. The most noticeable difference between the lymph folds and the other reproductive structures is the epithelium which is columnar epithelium. This feature readily distin— guishes the lymph folds from the round bodies, phallus and proctodeal fold but in turn makes it difficult to differentiate it from the uro— proctodeal fold of the cloaca. Other landmarks are present to enable differentiation between the lymph folds and the uroproctodeal fold.

At the level of the lymph folds the proctodeal fold is quite large. The p, levator cloacae is perhaps the most important landmark

as it is generally located directly ventral to the lymph folds. The p,

levator cloacae does not lie beneath the uroproctodeal fold. The uro-

proctodeal fold contains the muscularis mucosa which terminates prior

to reaching the lymph folds. Most of the more lateral of the parasagit—

tal sections of the lymph folds usually cut through the more medial

aspect of the vascular body. The vascular body appears ventral to the pp levator cloacae and just slightly cranial in the more lateral sections

of the lymph fold.

As previously stated the lymph folds are found to be covered with

columnar epithelium. The transition from the stratified squamous occurs

on the structures which lie caudal to the lymph folds and this change

is rather abrupt. For example, this change is observed to occur about

2/3 of the way down the cranial surface of the proctodeal fold in the

more lateral sections which pass through the lymph folds and the procto-

deal fold. The columnar epithelium continues down the remaining portion

of the proctodeal fold and then up the caudal surface of the lymph fold.

More medially the ventro-cranial surface of the round body similarly

changes from stratified squamous to columnar epithelium continuing down

the remaining cranial surface of the round body.and then up the caudal

surface of the lymph fold.

The columnar epithelium is found to have ovoid to round nuclei

present within the cells, and is generally located towards the base of

the cell. The epithelium follows the various depression and ridges of

the lymph fold.

Deep to the columnar epithelium lies the lamina_propria. This

layer contains numerous lymphocytes and many small blood vessels. The

supporting framework of this area appears to be composed of a fine 91 network of reticular fibers in the area just below the epithelium.

Deep to this area is a central core composed of collagenous fibers.

The only major characteristic difference between the lymph fold and the other reproductive structure of the proctodeum.is the presence of the columnar epithelium and the lymphocytes present just deep to the epithelium. The core of connective tissue contains the channels and the same types of connective tissue as the other reproductive structures. DISCUSSION

During copulation the male White Leghorn fowl ejaculates semen

which is composed of a portion from the ejaculatory papillae and a por-

tion from the lymph folds. In order to accomplish the copulatory act

many structures come into play in the deliverance of semen to the female.

The erection and eversion of the phallus presents the most obvious

change during copulation. This is brought about by stimuli through the

_p. pudendus. A.neuro-vascular mechanism.which involves the p, pudendus

in some way stimulates the vascular body to filter the blood passing

through its capillaries. The p, pudenda interna supplies the vascular

body. The arterial branches take a tortuous course after entering the

vascular body. Draining the vascular body by way of the y, pudenda

interna which in its course parallels closely the pudendal artery.

The capillaries within the vascular body,lie close to lymph

-channels which collect the filtrate from the blood and hence conducts

it to lymph channels of larger size. These channels, in turn, trans-

port the filtrate to the phallus, round body and lymph fold. These

latter three structures become distended with lymph fluid; the round

body becomes the largest structure. The round bodies due to their in-

creased size push the phallus, which forces it ventrally through the

cleft in the proctodeal fold and the round bodies move medially to

occupy the space previously held by the phallus, therefore, the round

bodies lie in close proximity to their homologue of the opposite side.

92 93

The movements coordinate with the lymph fold to establish a groove just caudal to urodeum.and the ejaculatory ducts. The end result is a groove overlying the ventral lip of the cloaca.

A thin, transparent fluid is added to the semen in varying amounts at the time of ejaculation. A.more rapid ejaculation when abdominal massage is used for semen collection, causes the bird to produce semen which consists mainly of the material from the ejaculatory papillae and relatively little from the lymph fold. Manipulation that produces de- layed ejaculation is mingled with a more copious quantity of seminal fluid. Nishiyama (1955) reported that the seminal fluid was discharged between the cells of the columnar epithelium of the lymph fold and sup- ported his evidence with gelatin injections. He did not find gelatin passing through the epidermis of the phallus or round body, both organs of which are covered with a stratified squamous epithelium. Thus, the type of epidermis found covering the reproductive structure appears to influence the point of discharge. The channels in the connective tissues of the phallus and round bodies probably are not involved in discharging fluid but here they may function to establish turgidity of these organs as discussed in the next paragraph.

The p. levator cloacae plays an important role in the eversion

process and the release of the lymph fluid from the lymph folds. The pair of muscles appear to suspend the cloaca from the tail. They are found lateral to the lymph channels of the phallus and round bodies and lie between these and the vascular body. When the muscles contract, they pull on the ventral part of the cloaca which compresses the lymph channels located between the vascular body and the phallus-round body— lymph fold group. This contraction probably forces fluid into the 94

channels of the lymph fold, round body, and phallus. Since the phallus

and round bodies apparently do not exude any seminal fluid, the lymph

fold becomes the only exit by which the fluid pressure can be relieved.

This is added to the semen flowing forward to the exterior. The reverse

process is accomplished by relaxation of the muscles and the channels

can again fill with seminal fluid.

In the male, the tail is moved up and down during copulation.

The p, levator cloacae is attached to the lateral rectrix, therefore,

the levator muscle will be raised or lowered by the movement of the

powerful elevators and depressors of the tail. These larger muscles

can indirectly act on the phallus by changing the position of the tail

and thereby change the position of the p, levator cloacae and its direc—

tion of pull. The p. depressor coccygeus is one of the depressors of

the tail. When the depressor coccygeus muscle contracts, the p. levator

cloacae will be taut because it makes a sharp bend at the cranial border

of the p, contractor cloacae. If the p, levator cloacae itself con-

tracts while in this position, it will increase the pressure on the

Achannels. Contraction of the p, levator coccygeus elevates the tail

(Fig. 6). This also in the depressed condition exerts a pull on the

.p, levator cloacae. The latter muscle continues, therefore, to exert

pressure on the seminal channels. Either extreme position augments the

discharge of fluid. The cock does not normally carry his tail in either

of these extreme positions.

Since the lymph fold is the exit organ for seminal fluid, when

the pressure is relieved, its channels will refill upon relaxation of

the p, levator cloacae. Thus, as the tail rhythmically moves up and

down, there are alternating contractions of the p, levator cloacae with

95 a subsequent discharge and restitution of fluid. Both processes occur during an ejaculation. The ejaculation is a few seconds in duration

(Burrows and Quinn, 1937) which is a sufficiently long period of time to allow for several discharges and restitution cycles.

The production of pressure that produces a discharge of fluid from the lymph fold, produces only turgidity in the phallus and round bodies because there is no place for the fluid in the channel to go.

The p, sphincter cloacae may also have an effect on copulation.

When it contracts, it pushes inward pressing on the entire proctodeum.

This pressure by undercutting the proctodeal fold may aid in the eversion of the phallus and preventing return flow of channel fluid, thereby holding the phallus in an erected state. This muscle may also put pressure on the vascular body. Such compression could act in increasing the filtration rate of the fluid from the capillaries into the lymph channels.

When the reproductive structures of the proctodeum are everted the lymph folds are moved to a position just caudal to the ejaculatory papillae, and therefore, come in close proximity to the emerging semen.

The shifting of the lymph folds brings them together in such a way that their surfaces form a funnel, draining toward the phallus and round bodies. Semen mixed with seminal fluid leaves the cloaca by way of the everted groove formed by the round bodies and phallus.

The fluid which remains in the tissue drains into lymphatic ducts that parallel the pudendal artery and veins and presumably reach the thoracic duct. Once again the birds copulatory organs are in a quiescent state. This is permitted by the relaxation of the p, levator cloacae and the p, sphincter cloacae.

SUMMARY

The gross and microscopic anatomy of the structures involved in

the production of seminal fluid in the chicken are discussed. The

phallus, round bodies,lymph folds and vascular bodies were found to be

the structures directly involved in seminal fluid production. Sur-

rounding structures were discussed for orientation and illustrations

were presented to complement the discussion.

The cloaca is composed of three chambers; proctodeum, urodeum,

and coprodeum. Externally it appears as two lips, a larger dorsal lip

and a smaller ventral lip. Its surface is covered with epithelium

characteristic of the general body surface.

The proctodeal fold arises from the margin of the lips and forms

the cloacal opening by its incomplete central fusion.

The proctodeal cavity is the most caudal of the cloacal chambers.

The phallus, round bodies and lymph folds lie in this chamber. The opening to the cloacal bursa is found in the dorsal aspect of this chamber.

The uroproctodeal fold forms the cranial boundary of the proctodeum and the caudal boundary of the urodeum. The urodeum is the middle chamber of the cloaca. The ejaculatory papillae and ureters empty into

this chamber.

The uroproctodeal fold forms the cranial boundary of the urodeum and the caudal boundary of the coprodeum. The coprodeum is the most

96 97

cranial of the three chambers of the cloaca and the rectum empties into

this chamber.

The p,_§phincter cloacae, p, contractor cloacae, p, transversus

cloacae, p, levator cloacae and p, dialator cloacae are muscles directly

associated with the cloaca. Other muscles of the caudal area indirectly

act on the cloaca.

The pp_ppdenda interna supplies the vascular bodies and the re-

productive structures of the proctodeum. The y, pudenda interna drains

the structures and closely parallels the course of the p, pudenda interna.

The p, pudenda is closely associated with these vessels. The cloacal

ganglion was found to be close to the vascular body.

The vascular bodies lie ventral to the cloaca and are composed

of a network of capillaries. Endothelial lined channels were found

originating next to the capillaries and draining to larger channels

which in turn left the vascular body and entered the phallus, round

bodies and lymph folds.

The phallus was found to lie in the ventral midline of the

proctodeum. Stratified squamous epithelium composes its epithelium.

The dermis lies deep to the epidermis with a core of connective tissue

lying deep to the dermis. The channels which originate in the vascular

body extend into the-connective tissue core and the dermis.

The round bodies are paired structures which lie on either side of the phallus. Their epidermis is composed of stratified squamous

epithelium. Deep to the epidermis is connective tissue which contains

the channels. These channels connect with the channels entering the phallus. 98

the lymph channels. These were found to connect with the phallus and round bodies. In addition numerous lymphocytes were found in the lymph

fold. The lymph fold has many of the features of the lower digestive

tract but lacks a muscularis mucosa.

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103

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FIGURE p_—- Caudal view of the external surface of the cloaca

illustrating the position of the dorsal and ventral lips

and the feather tracts and apteria directly associated

with them. The numerals l, 2 and 3 indicate the position

that the forceps attach in Figure 2. Cloaca] apterium

Dorsal lip

‘. I., " ’5‘? rm 35!, i- “'1, ' 3gp}: \;,| ”'é , if '1'": , , l ‘t> 7" ‘ 3 ~ u”:- :-;.’.’ . .'v‘ I; 0 ’.4-- I I “up. * ‘ “’k‘ipzpp '\’ ‘»"‘.-~"5‘ . ». . I i. I. .97“. - I‘ a ‘ "‘1‘ _-'.h ,~ ~‘ -,;:;;:;7‘ .. Cloaca] cnrclct a. ‘ .1 ~ ‘ °‘ ‘. ‘ ' 512W; pi. “Wk “we ‘~ War ,;,;,ws.' ,._ " r .42". A: ,._ Mmp‘mlﬁﬁfl’w W g; 1) ventral up a e " w. heapi/yh

7-: ;,. x I. - f 0.1 ‘ \ 4: "' 57-121 1'“ J" ‘k‘ ,‘I. \ I“ r 2 (\- .{q_ “ w 0.. ﬂu.“ A ,, 15, ﬂ . 1, Medal abdominal tract 'n H .. .. "« ~

1.0 cm. J-

106

FIGURE_g —- Caudal view of the cloaca with the dorsal lip elevated.

Forceps are placed at points 1, 2 and 3 as indicated in Figure l

and pulled dorsally. The formation of the cloacal opening

formed by the incomplete central fusion of the proctodeal fold

is shown. Cranial to the cloacal opening is the proctodeal

cavity. Points A, B, C, D and E indicate the position where

the forceps attach in Figure 3. 2 Margin of dorsal lip Attachment of proctodeal fold to margin of dorsal lip 3

Triangular swelling of dorsal lip Free edge of procrodeal fold

Opening to portion cloacal bursa Proctodeal fold - free

Uroproctodeal Junction of dorsal fold and ventral lips

Base of phallus , , ., / .. z . Median “Pl" \..,\;\ ‘_ 3;," r':,.,,i .’ 4P ,,., Proctodeal fold - attached portion \.‘ \\{£,W " /' Margin of ventral lip \ '\\. \ \, ~/ ..‘-l ’ ’ ’~ / '1' I Abdominal - wall

108

FIGURE 2_-- Caudal view of the proctodeal cavity and its contents.

Forceps are attached at points A, B, C, D and E as indicated

in Figure 2 and pulled outward. The opening to the cloacal

bursa, the location of the reproductive structures of the

proctodeum and the uroproctodeal opening are illustrated. Margin of dorsal lip Opening to cloacal bursa Triangular swelling of dorsal lip Proctodeal fold

Uroprocmdeal fold

Uroproctodeal opening

Lymph fold Attachment of proctodeal fold to lip Round body Ventral lip

Phallus ”.8 é—W/Mﬁ’

1.0 cm.

110

FIGURE §_-- Caudal view of the proctodeal and urodeal cavities.

The proctodeal fold has been displaced. The ventral forcep is

attached to the phallus and then pulled ventrally. The uro-

proctodeal fold has not been disturbed on the right side and

reveals a slight protrusion of the ejaculatory papilla into

the proctodeum. The uroproctodeal fold on the left side is

displaced to illustrate the lateral extent of the ejaculatory

papilla and its relationship to the opening of the ureter. Margin of dorsal lip Forceps pulling uroprocrodeal fold Triangular swelling of dorsal lip away from urodeum \ Proctodeal fold - dorsal lip

Opening to cloacal bursa Opening of ureter Lateral wall of procrodcum Urocoprodeal fold .\ . ,

Free edge of uroproctodeal fold '

Eiaculator y P a P illa - ri g ht side Ejaculatory papilla - left side Proctodeal fold - ventral lip Opening to coprodeum '1 ‘l’ \‘d‘ ,\.\ 1;). ;/ Margin of ventral lip

REFIJMP Cephalic base of phallus L0 cm. Forceps holding phallus

112

FIGURE g -- A sterogram of the cloaca which illustrates the various

cavities. The coprodeum is most cranial followed by the

urodeum and proctodeum. The relative size and shape of the

chambers is illustrated along with the position of the

ejaculatory papilla and ureter of the urodeum and the phallus

and round body of the proctodeum. The duct of the cloacal

bursa is also illustrated. M. sphincter cloacae Muscular-is mucosa Dorsal lip Cloaca] bursal duct Phallus COPRODEUM Proctodeal fold Ureteric opening Round body-right side Round body-left side Urocoprodeal fold M. levator cloacae Ejaculatory papilla PROCTODEUM Uroproctodeal fold Muscularis mucosa

URODEUM Ventral lip M. spbim‘ter cloacae 114

FIGURE §_-- Caudal view of the musculature related to the cloaca.

This illustration presents the muscles of the area and their

relation to the cloaca and the vascular body. The tip of the

tail lies in the same vertical plane as the 2° sphincter

cloacae. The right side has had the connective tissue and

fat dissected away to reveal the muscles as separate structures.

The right side, in addition, has a section excised from the

39 transversus cloacae. The E: sphincter cloacae has been cut

and pulled dorsally to reveal the vascular body. M. adductor rectricum

M. levator cloacae M. depressor coccygis M- depressor Mild“ M. lateralis cocqgis

M. contractor cloacae M. dialalor cloacae M. spbitu'ter cloacae M. transversus cloacae

.\ . ,’ M\\ .\

Vascular body ' ’ . ///, “'1‘: \ . = .. _. \ Terminal end \\\ of pubic bone

#ﬁE‘WTA/& ‘

Pubic bone

Abdominal fascia [.0 cm.

116

FIGURE Z_-- Lateral view of the muscles related to the cloaca.

In this illustration the tail lies in a more horizontal

plane than is found in Figure 6. The muscle components

surrounding the cloaca and composing its dorsal and

ventral lips are illustrated. M. lateralis caudae

M. levator caudae M. levator coccygis

M. adductor rectricum M. W accygis "J ll": 1". ti/l/ / M. [cum cloacae

M. contra!" cloacae M. spbiscter cloacae

Cloacal opening _J

M. depressor caudae

Pubic bone

1.0 cm.

n..'.. I ”Elm” :

118 __—-““

FIGURE §_-- Ventral view of the arterial and venous supply to the

vascular body and the relationship of the vessels to the

ureter and ductus deferens. Aorta descendens

A. ischiadica Ductus deferens

A. sacralis media Ureter A. sacralis lateralis Caudal lobe of the kidney A. mesenterica caudalis V. coccygo-inesenterica

V. hypogastrica

A. pudenda communis V. pudenda conununis

V. coccygis A. coccygeus media A. pudenda externa Ranus muscularis caudae

A. pudenda interna V. pudenda externa

Ramus muscularis caudae V. pudenda interna

Cloaca Vascular body

ROFWM/6—’ Pubic bone 120

FIGURE_2 -- Parasagittal section taken to the left of the cloaca

as indicated in the line drawing of the cloaca. The rela-

tionship of the vascular body to the ductus deferens, ureter

and m, levator cloacae is illustrated.

Smoorh muscle of feather follicle Ureter: Epithelium Cut shafts of feathers Mucosal layer Muscularis mucosa

Blood vessels

Connective tissue Dorsal lip: Duetus deferens Fold of ptOCtodeal w,“ 5". . m '3 i‘ﬁ" ‘ M. dialator cloacae Proctodeal cavity - 5 ' ..\' M. levator cloacae Proctodeal wall: . "s

Mucosa Submucosa Nerve cavity Skin: Coprodeal Epidermis Coprodeal wall:

Dermis Mucosa Subcutaneous layer Submucosa M. sphincter cloacalis Muscularis mucosa: Inner longitudinal muscle

Wrinkles of skin Outer circular muscle

Ventral lip: Vascular body M. sphincter cloacalis Channels of vascular body M. transversus cloacalis

Apterial muscle

Abdominal wall

122

FIGURE lQ_-- Frontal section taken through the cloaca at an oblique

angle as represented by the line drawing of the cloaca. In

orienting this section, Figures 1 and 5 are helpful. The

urodeum is not found in this illustration as the section

has been taken dorsal to it. Cloacal opening Dorsal lip M. spbincter cloacae Proctodeum Submucosal glands Procrodeal fold-dorsal lip Procrodeum External surface of Reproductive struCtures procmdeal fold L YmP h C h anne l 5 _ Proctodeal fold- ventral lip Proctodeum M. levator cloacae M. depressor caudae M. dialator cloacae M. contractor cloacae Vascular body Muscularis mucosa M .contractor cloacae Duetus deferens Duetus deferens Ureter M usculart's mucosa CoPrOdeum ___7‘ ‘ ”M”

1 mm.

124

FIGURE ll_-- Low power 10X drawing of the tissue of the vascular

body showing the lymph channels and the numerous capillaries.

The section is taken at the edge of the vascular body so as

to include a portion of the connective tissue which surrounds

it. Red blood cells

Lymph channels

Capillaries Supporting tissue

‘ a . ‘.gz“; Connective tissue ‘-“.'""__':.'”./.._ 43-» 1;:- ““/’cd::... .ﬁ,‘ 3473’ . "in. "'2"; ' , , , ~2— i'CWir-"fli 2‘5; " ,f 1‘ '.‘d: _ .9 Artery 32:94 f, .. ﬁ*.'.~'-,"-'-'eh‘ ‘, 5; #13,," ‘£95: ' . . . a).2m 1,..- r.- I‘FWNO- I‘m 126

FIGURE_lg'—— Section (93X) of the tissue of the vascular body

illustrating the relationship of the lymph channels to

the capillaries. Capillary Red blood cell

Lymph channels

Fibroblast

Endothelial cell l—l 0.01 mm. 128

FIGURE l§_-— Mid—saggital section taken through the phallus as

illustrated in the line drawing of the reproductive

structures of the proctodeum. The location of the lymph

channels within the phallus are shown.

DORSAL

M .5 c

EP r m

Arteries

Dermis

Red blood cells

. ._.

.3: CRANIAI. \b“ a m m tve tissue

Lymph channals

29.5 Fer/”$- Nerve trunk

VENTRAL

0.1 mm. 130

FIGURE 14 -- A sterogram which illustrates the course of the lymph

channels from the vascular body to the reproductive structures

of the proctodeum. In orienting this illustration Figure 5

is helpful. Lymph fold Round body Duetus deferens - left side Con necrive tissue M uscularis mucosa

Phallus Round body PROCTODEUM - right side

M. levator cloacae URODEUM Eiaculatory papilla

Lymph channels I i .' Urocoprodeal fold rigid; ‘l Uroprocrodcal fold l .i Vascular body

PROCTODEUM

Muscularis mucosa Folds of caudal wall of proctodeum