Arch. histol. jap. Vol. 23, n. 5 (July 1963). P. 447-459.

Dept. of Anim. Husb., Fac. of Fish. and Anim. Husb., Hiroshima Univ., Fukuyama, Japan.

Histological and Histochemical Studies on the Oviduct of the

Domestic Fowl with Special Reference to the Region of

Uterovaginal Juncture.

鶏 の 卵 管, と く に 子 宮 と 腟 の 移 行 部 の 組 織 学 的 お よ び 組 織 化 学 的 研 究.

Shunsaku FUJII 藤 井 俊 策.

(Received May 30, 1963.)

The histological structure of the oviduct of the domestic fowl has almost com- pletely been investigated by many workers, including SURFACE (1912), GIERSBERG (1921, 1922), FROBOSE (1928), BRADLEY (1928), and RICHARDSON (1935). SURFACE studied mainly the histological structure of the oviduct itself. RICHARD- SON observed in detail the function and histological s structure of the gland of the ovi- duct. At present, the oviduct is generally divided into five portions: the infundi- bulum or funnel, the magnum or albumen secreting portion, the isthmus, the uterus or shell-gland region, and the vagina. Each portion has its particular structure and physiological function for egg production. In addition, some workers have identified another portion as the region of juncture, where one type of mucosa intermingles with another type. For instance, GIERSBERG (1922) distinguished the cranial half of the infundibulum as the 'Trichter'and the caudal half as the 'Tube'. RICHARDSON, (1935)also subdivided the infundibulum into 'funnel'without glandsand the 'chalazi- ferous region'with glands, and insertedthe 'isthmo-uterineregion' between the isthmus and the uterus. In spite of such large number of histological observations as these, little has been reported on the histochemistry of the oviduct. In the course of histological and histochemical studies of the fowl oviduct, the author found the existence of characteristic mucous zones both at the caudal end of the uterus and the cranial end of the vagina. Each zone had definite histological and histo- chemical characteristics which distinguished it from its adjacent portion. The present paper deals mainly with morphological findings of the region of uterovaginal juncture.

I. Materials and Methods. The oviducts collected from adult White Leghorn hens just after decapitation were used. The structure of the oviduct changes largely in accordance with the state of laying. Therefore, the oviducts used had been removed from nonlaying and laying hens in varying states of laying; that is, before ovulating, after laying, and stages where eggs were at different levels of the oviduct. They were classified according to the purpose of investigation and subjected to some suitable methods. For observation of general histological structure, they were fixed in BOUIN's and ZENKER's solution and made to paraffin sections 5-10μ thick, which were stained with hematoxylin

447 448 S. FUJII:

and eosin and by HEIDENHAIN's azan and iron-hematoxylin methods. For demonst- ration of polysaccharide and mucopolysaccharide, they were fixed in CARNOY's solu- tion and 95% alcohol and stained by the periodic acid-SHIFF (PAS), LISON's alcian blue, and BEST's mucicarmine and mucihematein methods. For demonstration of the activities of alkaline and acid phosphatases, material was immersed in acetone, sectioned, and treated by GOMORI's calcium phosphate method and lead phosphate method, respectively. Some material was fixed in BAKER's calcium formalin and

sectioned with a freezing microtome at a thickness of 15-20μ The sections were stained by the following techniques: for fat substances, BAKER's sudan black B and GIACCIO's sudan III stain, for phospholipids BAKER's acid hematein, MENSHIK's Nile blue and CIACCIO's sudan stain, for cholesterin and its ester SHULTZ's test, OKAMOTO's method and FEINGIN's digitonin method. In addition, the polarized- light method was employed for demonstration of cholesterin.

II. Results.

A. Macroscopical Observation. Macroscopically, the uterus is a somewhat flattened, elongated sac with trans- verse bands. The vagina is a narrow muscular tube, extending from the caudal end of the uterus to the cloaca. The boundary between the uterus and the vagina is indicated by the presence of a sphincter muscle. In more detail, the enlarged body of the uterus is constricted gradually in funnel shape as it approaches the narrow vaginal orifice, where the uterus ends abruptly. Caudal to the orifice, the vagina at first curves a little dorso-cranially, forming the first flexure. Then it ascends along the dorsal wall of the uterus for a short distance, about 1cm, enclosing the outer, longitudinal muscle of the uterus. It again turns suddenly backwards by forming the second flexure, after which it becomes smaller in caliber towards the cloaca, convoluting slightly in its course (Fig. 1). The inner surface of the uterus is thrown into a number of leaf-like folds of mucous membrane showing a faint rose pink color. On the other hand, that of the vagina is white in color and forms low, regular longitudinal folds. In the uterovaginal junc- ture, the transition of the mucous membrane is grad- ual, so that no clear demarcation is noticed, except a vague constriction around the vaginal orifice. Fig. 1. Outside appearance of the Careful observation of the terminal portion of the uterine and vaginal regions of the uterus indicates, however, that a narrow, ring- oviduct in a laying hen. Abbrevia- shaped zone, about 0.5-1cm wide, around the tion: Ub uterus proper, RU recessus vaginal orifice differs distinctly from the main por- uteri, Vg vaginal glanid region, Vp vagina proper. About 1/2. tion of the uterus in the color and shaps of the folds of mucous membrane. In this zone, the mucoss presents a characteristic grayish-white color, forming low, somewhat regularly ar- Histological and Histochemical Studies on the Oviduct etc. 449 ranged, longitudinal folds. These folds represent exactly an intermediate type between the uterine and the vaginal mucosal folds. This zone can be recognized by a naked eye, especially by the color of its mucosa, but the shade of its mucosa varies according to the activity of the oviduct. In general, this part of the uterus appears grayish- white in nonlaying hens, as well as in laying hens containing no egg in the uterus. Therefore, it is very characteristic of these hens. In hens which have just expelled eggs, this zone appears faint pink, with its regular color faded. Therefore, it is not so distinctly differentiated as before. The change in mucosal color suggests that some structural changes have occurred in the epithelium during the formation of egg-shell or expulsion of the egg. Accordingly, the caudal end of the uterus has not only these macroscopical features, but also such definite microscopical ones as mentioned below. So the author calls this portion as the recessus uteri, distinguishing it from the main portion of the uterus (hereinafter referred to as the uterus proper).

Fig. 2. Inside appearance of the region of uterovaginal juncture. For abbreviations, see Fig. 1. Fig. 3. The mucosa of the uterus proper in

a laying hen. Note luxuriant uterine glands.

Hematoxylin and eosin (HE) staining. ×190.

The beginning of the vagina, about 1cm long, between the first and the second flexure as mentioned above, is much larger in outside and inside diameter than the remainder of the vagina (hereinafter referred to as the vagina proper). The mucosal folds of the inner wall are lower and wider in the former than the latter. In addition, this part of the vagina is characterized histologically by the presence of many large tubular glands in the lamina propria which are to be mentioned below. So it is called the vaginal gland region, distinguishable from the vagina proper (Fig. 2).

B. Histological Observation.

As is generally known. the uterine mucosa is thrown into numerous folds with 450 S. PUJII: a few secondary ridges, which are lined by a pseudostratified epithelium composed of two kinds of cells, ciliated columnar and goblet cells. Situated in the lower position, goblet cells are extremely slender and scattered among tall ciliated cells located in the upper position. They are slightly positive to mucin stains in the PAS method, but are not stained with such dyes as alcian blue, mucicarmine, and mucihematein. The lamina propria is vascular and packed densely with highly branched tubular glands, known as the uterine glands. The glands are of large cuboidal cells with centrally located small, round nuclei (Fig. 3). Toward the caudal end of the uterus, the uterine glands decrease in number and gradually changes into small, simple tubular glands. Each gland has a narrow lumen

Fig. 4. The mucosa of the recessus uteri in a laying hen. Note

small tubular glands scattered in loosely arranged connective tissue. HE staining. ×190.

Fig. 6.

Fig. 6. The high-power magnification of Fig. 5. HE staining. ×400.

Fig. 5. The mucosa of the juncture of the recessus

uteri and the vaginal gland region. Note small glands

mingling with large ones. HE staining. ×190.

Fig. 5. Histological and Histochemical Studies on the Oviduct etc. 451 surrounded by a few low cuboidal cells. Although it seems to be different from the uterine gland, the cytoplasm of its glandular cells contains fine acidophilic granules characteristic of the uterine glands. In the recessus uteri continuous to the previous region, however, the surface of the fold is comparatively irregular, owing to an increase in secondary ridges. The lining epithelium has still essentially the same composition, although its goblet cells become smaller in number and larger in size than before and stainable with all the mucin stains employed before. It should be noted that the lamina propria of this region is composed of avascular loose connective tissue and has a few small glands scattered (Figs. 4 and 6). These glands are commonly of simple tubular type and occa- sionally of bifurcated type, opening into a shallow groove between the secondary ridges. They are narrow, about 3μ in diameter, and lined by a single layer of low cuboidal cells, which are about 7μ in hight and contain a round, somewhat large nucleus in the basal cytoplasm. These cells have not such acidophilic granules as cha- racteristic of the uterine gland in their cytoplasm. PAS-positive granules, which can- not be detected in the uterine gland, are found in small numbers in the cytoplasm of these glandular cells, but abundantly in that of the cells near the glandular opening. No material tested was affected by the saliva or stained with alcian blue and others. Neither alkaline nor acid phosphatase is present in the epithelium. Where the recessus uteri merges in the vagina, secondary ridges develop well on the surface of main folds. Here the above-mentioned tubular glands disappear and large tubular glands (hereinafter referred to as the vaginal glands) appear. Two types of glands, therefore, are intermingled in the same fold, as illustrated in Figs. 5 and 6. The vaginal glands become more and more numerous toward the vaginal gland region. In the beginning of the vagina, or the vaginal gland region, secondary ridges develop more from the mucoua than in the reccessus uteri and less than in the vagina proper. The covering epithelium of the vaginal gland region is composed of the same type of cells as mentioned above, but goblet cells have increased again in number and size, showing a tendency to gather in the depth of the groove. The content of the goblet cell exhibits a character of strongly acid mucopolysaccharide. The most strik- ing, distinguishable property of this region is the presence of the vaginal glands in the lamina propria of the mucous membrane. These glands are of simple tubular type. As shown in Figs. 7 and 8, they are located in abundance in a relatively dense con- nective tissue. The body of the gland extends from a shallow groove lying on the apical and lateral surface of a fold to the core of the fold, being straight or bending slightly. The gland consists of tail columnar cells, about 25μ in height, and its lumen is broad, about 14μ in diameter. The glandular cell has a round nucleus containing a clear nucleolus and located regularly close to the basement membrane. Its cytoplasm is finely vacuolated and has an unstained empty area, where lipids are deposited, in the supranuclear portion. Neither PAS positive granules, appear in the above-men- tioned gland, nor mucopolysaccharide is present any longer. The glandular cells are intensely positive to acid phosphatase, but do not react with alkaline phosphatase. Toward the vagina proper, the vaginal glands gradually become shallow and finally continue to grooves between secondary folds. 452 S. FUJII:

Fig. 8. High-power view of the vaginal gland.

The lumen is wide and is lined by a single layer of

tall columnar cells. Nuclei are arranged regularly

close to the basement membrane. The lumen con-

tains a large number of sperms. HE. staining.

×400.

Fig. 7. The mucosa of the vaginal gland

region in a laying hen. Note development

of secondary folds and presence of many

vaginal glands in relatively dense connec-

tive tissue. HE staining. ×190.

Fig. 9. The mucosa of the→ vagina. The fold is narrow and has secondary ridges ar- ranged parallel HE staing. ×190.

In the inactive oviduct, the vaginal glands are not so remarkably atrophied as the other glands of the oviduct; they are about 30μ in outside diameter and 12μ in depth from the surface of the epithelium. As illustrated in Figs. 13 and 14, atrophied vaginal glands are irregularly round in form at cross section. Hence, it may be said that no vaginal glands have been affected intensively by the functional change of the oviduct. Beyond this region, the vagina reveals its proper structure. Its mucosa is thrown into tall longitudinal folds with numerous secondary ridges, which are arranged paral- lel to the folds in a transverse direction. Here goblet cells are crowded in the bottom of the groove and exhibit a strongly positive reaction to all mucin stains, especially alcian blue (Fig. 9). Histological and Histoehemical Studies on the oviduct etc. 453

C. Observation of Lipids.

When frozen sections are fixed in BAKER's calcium formalin and stained with Sudan black B, variable amounts of sudan-positive granules are observed exclusively in ciliated cells covering the mucous membrane of the recessus uteri. These granules are not found in the cover- ing epithelium of the uterus proper nor in any portion of the oviduct (Fig. 10). The same result is obtained from Sudan III staining. It should be noted, however. that the granules of lipids vary extensive- ly in amount and location in the cytoplasm according to the functional activity of the oviduct. As is seen in Figs. 11 and 12, in

Fig. 10. The mucosa of the

uterus proper in a laying hen

with no egg in the oviduct.

Note the deposition of sudan-

positive granules. Sudan black B staining. ×190.

Fig. 11. Deposition of Sudan-positive granules

in the epithelium of the recessus uteri in a

nonlaying hen. Note a large amount of sudan

granules in the epithelium. Sudan black R staining. ×190.

Fig. 12. The high-power magni-

fication Fig. 11. Sudan-positive

granules in ciliated cells. They are deposited on either side of the nuc-

leas, forming concentrated masses.

Sudan black B staining. ×600. 454 S. FUJII:

laying hen with no egg in its oviduct, a large amount of lipids is deposited on either side of the nucleus of the ciliated cell, appearing as a conglutinated mass. Quite a similar finding was obtained from nonlaying hens. On the contrary, after the release of an egg, lipids are deposited a little and distributed throughout the cytoplasm as discrete droplets. From these findings, it is evident that lipids have been discharged in the uterine cavity before or by the time an egg is laid. Thus, a rich accumulation of lipids in the epithelium gives a histochemical feature to the reccessus uteri. The lipids contained in the ciliated cells, however, decreases progressively in quantity toward the vaginal epithelium. In the vaginal gland region, no Sudan-positive granules are found in the cover-

Fig. 14. Deposition of abundant sudan-positive

granules in the vaginal glands of a nonlaying hen. The granules form concentrated masses.

No deposition of sudan-positive granules is seen

in the epithelium of this region. Sudan black Fig. 13. Deposition of sudan-positive B staining. ×190. granules in the vaginal glands of a hen with an egg in the oviduct. Sudan black

B staining ×190.

Fig. 15. The high-power magnification of Fig. 14. Fig. 16. Deposition of Sudan-positive granules in

A large amount of sudan-positives is deposited in the vaginal glands of a laying hen with no egg in the supranuclear region. Vaginal glands are irregu- the oviduct. The picture closely resmbles Fig. 15.

larly round in form. ×600. Sudan black B staining. ×400. Histologicaland Histochemical Studies on the Oviduct etc. 455

ing epithelium, although a variable amount of these granules is deposited in the cells of the vaginal gland (Fig. 13). The lipids presented here are the same substance as recognized in the above-mentioned region, and also manifest varying phases according to the functional change of the oviduct. The deposition of lipids in the vaginal gland cells of a resting hen is shown in Figs. 14 and 15, and that in the same glands of a laying hen in Fig. 16. These photographs give quite a similar finding, in spite of the presence of great differences in the activity of the oviduct between the birds. As is clear in these photographs, lipids are concentrated in quantities in the supranuclear region, scarce in the infranuclear region, and entirely absent in the luminal cyto- plasm. This phase, therefore, is considered to he an accumulation stage of lipids. After an egg is expelled, lipids decrease markedly in amount and are deposited as droplets of varying sizes (Figs. 17 to 19). Their distribution in the cytoplasm also differs in individual glands; they are located mostly in the basal or the apical part

Fig. 17. Deposition of sudan positive granules in vaginal glands just after expulsion of an egg. A few lipid granules are deposited in various loca- Fig. 18. For explanation, see Fig. 17. tions and sizes. Sudan black B staining. ×400. ×006.

Fig. 20. Glandular lumina of vaginal glands filled

with Sudan-positive secretion. Sudan black B stain- Fig. 19. For explanation, see Fig. 17. Note ing. ×400. transition between the groove of the epi-

thelium and the vaginal gland. ×400. 456 S. FUJII: of the cytoplasm in some glands. but are hardly present in the whole cytoplasm in others. This phase, therefore, is regarded as an exhaustion or an early accumulation stage of lipids. From these findings, it is obvious that the lipids are disintegrated into fine droplets and excreted in the lumen when the egg is expelled. Indeed, it has frequently been observed that the glandular lumen is filled with secretions stained dark-blue with sudan black (Fig. 20). The sudan positive granules pre- sented here are neither phospholipids nor glycolipids, since they give all negative results in the staining with BAKER's acid hematein, MENSHIK's Nile blue, and CIACCIO's sudan III for phospholipids and in PAS reac- tion. They are, however, positive in SHULTZ's test for cholesterin. Fur- thermore, they present a character of ester-forming cholesterin rather than Fig. 21. Lipid granules showing clear double simple cholesterin in OKAMOTO's refraction by polarized light. The mucosa, of the recessus uteri. ×190. method for cholesterin staining. In the digitonin method of FEINGIN, no cholesterin crystals are presented. On the other hand, these granules show a clear double refraction in the polarized-light method, as illustrated in Fig. 21. From these results, the sudan-positve granules are identified as cholesterin ester.

III. Discussion.

As described above, a characteristic mucosal zone was recognized at the caudal end of the uterus. The structural features are summarized: Macroscopically, the mucous membrane is thrown into regular longitudinal folds distinctly grayish-white and somewhat low. Microscopically, a few small tubular glands are located in the stroma of loosely arranged connective tissue of the mucosal lamina propria. Histo- chemically, large quantities of cholesterin ester are deposited in the epithelium. In this connection, the mucous membrane of the main portion of the uterus is covered with faintly pinkish, leaf-like mucosal folds. The mucosal lamina propria is studded by the so-called uterine glands. Concerning this zone of the uterus, reports have been made by SURFACE (1912), BRADLEY (1928), and RICHARDSON (1935), all of whom observed the fowl ovi- duct in detail. These investigators so classified that this zone was included in the uterus, but others overlooked such zone. Some consideration should be given, however, to the difference between the uterine glands and such glands of the recessus uteri as pointed out by the author. The latter glands apparently resemble the former, espe- cially those in the terminal portion of the uterus. As mentioned above, however, the glands of the recessus uteri differ from the uterine glands in the size of glandular body and the presence or absence of PAS positive granules and acidophilic granules. They rather resemble, in some respects, the following vaginal glands. At any rate, Histological and Histochemical Studies on the Oviduct etc. 457

the most outstanding feature of this zone consists in the deposition of cholesterin ester in the mucosal covering epithelium. No cholesterin lipids have been detected from the whole oviduct, except the following vaginal gland cells. It is of interesting to note that the mucosal color of this zone is closely related to the amount of cholesterin ester deposited in the covering epithelium of the zone. As already stated, the grayish mucosa, observed in nonlaying and laying hens with no egg in the uterus, has abundant cholesterin in the epithelium. The poorly grayish mucosa, noticed just after the expulsion of the egg, is scanty in deposited cholesterin, which has been almost exhausted by oviposition. From these morphological findings, it is suggested that the caudal end region of the uterus should be discriminated from the main portion of the organ and be called the recessus uteri. The role of the uterus in egg formation, as is generally known, is to secrete egg albumen and form egg shell. According to WARREN et al. (1915), the egg gets its shell pigment while it is in the uterus. No detail of the mechanism has been fully understood as yet. In the present investigation, no definite conclusion has been reached on the significance of the glands of the recessus uteri in egg formation. A characteristic mucosal zone, called the vaginal gland region, is distinguished at the beginning of the vagina, as already stated. It has structural features which are summarized as follows: Macroscopically, it is greater in outside diameter and has lower and wider mucosal folds than the main portion of the vagina. Microscopically, it is characterized by the presence of many large tubular glands (or vaginal glands), which contain a large amount of cholesterin ester. As for the vaginal glands, some workers reported their structure briefly. GIERSBERG (1922) and RICHARDSON (1935) found tubular glands at the beginning of the vagina, but their description was incomplete and covered no function of the glands. On the other hand, BRADLEY (1928) stated that the vagina has no glands in the ordinary sence of the word. This difference in opinion may have been derived from the diversity of the portion examin- ed. In the present study, the author definitely observed the presence of tubular glands in the vagina, especially in abundance in the mucosa of its cranial end. These glands are the same as those described by the previous workers. They apparently resemble the glands of the recessus uteri, but differ from them in the size of glandular body and the presence of cholesterin lipid in glandular cells. For this reason, the author suggests that the beginning portion of the vagina should be distinguished from the main portion of the organ and be called the vaginal gland region. According to ROMANOFF (1959), the vagina is related to the formation of the outermost layer of egg shell, or the cuticle layer, which is mucous in character. When an egg passes through the oviduct, the cuticle layer is formed by the secetion of goblet cells. In fact, numerous goblet cells containing mucopolysaccharide are observed in the epithelium of the whole vagina. The vaginal glands, however, are lacking in such mucous substance. Accordingly, their function could not be clarified in the present investigation. Judging from their position in the oviduct and their functional changes, the vaginal glands may play no essential role in egg formation. Presumably, they may partly contribute to the formation of the cuticle layer of egg shell. The author found that large numbers of sperms were present in the lumina of the vaginal glands in mated hens for a long time, and that the glands seemed as if they were a storehouse 458 S. FUJII: of sperms (Fig. 8). This finding will be discussed in a report to come. The cholesterin ester deposited in the covering epithelia of the recessus uteri and the vaginal gland cells was identified by using various differential staining methods for lipid. Its significance has not been elucidated as yet. It seems, however, that this substance may be discharged in the glandular lumina before or by the time the egg is expelled and may serve for the formation of the cuticle layer of egg shell in coopera- tion with the secretion of the vaginal glands.

VI. Summary. The region connecting the uterus and the vagina of the fowl oviduct was studied histologically and histochemically. It was found that there were a special mucosal zone at the caudal end of the uterus and another at the beginning of the vagina. Each zone was characterized by the following structures. 1. The caudal end of the uterus forms a ring shaped zone, about 0.5-1cm wide, immediately before the vaginal orifice. It is covered with a grayish-white mucous membrane and has low, somewhat longitudinally arranged mucosal folds. These folds differ from those of the main portion of the uterus, which are leaf like and faintly pinkish in color. This zone is usually distinguished by the mucosal color, which is variable according to the functional activity of the oviduct. The histological feature of this zone is the presence of small tubular glands which are different from the uterine glands and which are scattered in the stroma of loose connective tissue of the mucosal lamina propria. The histochemical feature of the zone consists in the deposi- tion of cholesterin ester lipid in its covering epithelium. The deposited lipid varies in quantity according to the activity of the oviduct. Generally, it is abundant in a stage when there is no egg in the oviduct, but it is quite scanty immediately after the ex- pulsion of an egg. 2. The beginning of the vagina forms an area, about 1cm far from the vaginal orifice, which is greater in diameter and which has lower and wider mucosal folds than the other portions of the vagina, the most striking histological feature of this zone is the presence of large tubular glands, which are called the vaginal glands. Histochemically, the glandular cells of the vaginal gland is characterized by the pre- sence of a large amount of cholesterin ester lipid. The functional change in the amount of this substance in the vaginal gland cells is the same as in the preceding uterine covering epithelium. 3. The function of the glands at the caudal end of the uterus and at the begin- ning of the vagina could not be clarified. Judging from their position and functional activity, these glands seem to contribute to the formation of the cuticle layer of egg shell. 4. The deposition of cholesterin ester lipid in the two parts mentioned above is the most outstanding feature of the region of the uterovaginal juncture. This sub- stance seems to play some role in the formation of the cuticle layer, since it is dis- charged when the egg is laid, Histological and Histochemical Studies on the Oviduct etc. 459

内 容 自 抄.

鶏 の卵管の子宮 と腟の移行部を組織学的 と組織化学 的に調べ た. 子宮 の遠 位部 (子宮窩 と呼ばれ る) を 注 意 して見 ると, 腟 にな る直前 で 約0.5-1cm幅 に わた り粘膜 の色 が変わ ってい るのが分か り, 灰褐色の木葉状 ヒダの子宮 粘膜 は, ここ で は高 さの低 い, やや規 則正 しい縦走 ヒダに移行す る. 組織学的 には粘膜 被蓋上 皮 は子宮部 と同様 に繊 毛細胞 と杯細胞の2種 の細胞よ り成 るが, 杯細胞 は少 な く, 大型で ある. 粘膜固有層 は 血管に乏 し く, 結合組織は著 しく疎で ある. ここに子 宮腺 とは異 な る小 型の管状 腺が 散在 して認 め られ る. 組織化学 的には, 被蓋 上皮 の繊毛細胞 は特異 的に多量の コレステ リン様脂質を 含む. この脂質 は卵の放 出時 に著 しく減少 す る. 腟 の起始 部の 約1cmの 間 (腟腺部 といわれ る) は腟の他の 部 分よ り少 しく径 が太 く, 粘膜 は高 さの低 い, 幅 の厚い縦走 ヒダで被れてい る. 被蓋上皮 はや は り 繊毛細胞 と杯細胞 よ り成 るが, 杯細胞は更 に少な くな り, 繊 毛細胞 は増 す. ここ の繊毛細胞 は もはや コレステ リン脂質を含む ことがない. 粘膜 固有層 はやや密 な 結合 組織 と変わ り, 大型の管状腺 (腟腺) が多数認 め られ る. 腟腺 は この部 の特 徴的存在 であ る. この腟 腺は大型であ るばか りでな く, 腺細胞 は多量 の コレステ リン様脂質を含む のが注 目され る. ここの脂質 もまた前 と同 じよ うに消長す る.

References.

Bradley, D. C.: Notes on the histology of the oviduct of the domestic hen. J. Anat. 62 (1928). -Frobose, H.: Die mikroskopishe Anatomie des Legedarmes und Bemerkungen uber die Bildung der Kalkshale beim Huhn. Z. mikr. -anat. Forsch. 14 (1928). -Giersberg, H.: Eihullenbildung der Vogel, sowie Entstehung der Vogeleier. Biol. Zbl. 41 (1921). -Untersuch ungen uber Physiologie und Histologie des Eileiters der Reptilien und Vogel, nebst einem Beitrag zur Fasergenese. Z. wiss. Zool. 120 (1923). -Richardson, K. C.: The secretory phenomena in the oviduct of the fowl, including the process of shell formation examined by the microincineration technique. Phil. Trans. Roy. Soc. Lond., series B. 225 (1935). -Romanoff, A. L. and A. J.: The avian egg. John Wiley and Sons, Inc., New York, 1949. -Surface, F. M.: The histo- logy of the oviduct of the domestic hen. Ann. Rep. Maine Agric. Exp. Station. 206 (1912). - Warren, D. C. and R. M. Conrad: Time of pigment deposition in brown-shelled hen eggs and in turkey eggs. Poult. Sci. 21 (1942).