Okajimas Folia Anat. Jpn., 68(4): 225-230, October, 1991

Considerations on the Morphology and Terminology of the Organs

By

Hidekazu WAKURI

Department of Veterinary Anatomy, School of Veterinary Medicine and Animal Sciences, Kitasato University Towada- shi, Aomori 034, Japan

-Received for Publication, July 15, 1991-

Key Words: Organ system, Organ, Sub-organ, Organelle

Summary: In anatomy, the morphological features of organs are captured in a variety of ways, and this allows wide interpretations of the terminology for organs. However, the present terminology is considered to include terms that require re-evaluation for appropriate ranking of organs. Organs should be understood in a proper perspective of their anatomical hierarchy and architectural characteristics. I consider that organs should be classified morphologically by the terminology of "organelle" on the cytological level, "sub-organ" on tthe histological level, "organ" on the macroscopic anatomical level, and "organ system", which may also be expressed as "apparatus" or "organa", on the level of systematic anatomy. I strongly demand that N.A.V.-N.H. (1983) acknowledge this hierarchial order and adopt the general term "organum".

A structure of a animal body composed of several Anatomica Veterinaria (N.A. V. , 1968, 1973) but, for organ systems. Anatomy is a science which aims to some reason, not in the current Nomina Anatomina morphologically investigate the world of external Veterinaria — Nomina Histologica (N. A.V.-N.H. , shape (= form) and internal structures of the body. 1983). They are absent also in the Nomina Anatomica The shape and structures of the body are studied Veterinaria Japonica (N.A.V.J.). from various scientific viewpoints such as cytology, Some investigators may consider that issues over histology, embryology, macroscopic anatomy, and the morphology of organs or interpretation of the systematic anatomy. However, anatomy does not terms descriptive of them are unimportant or mar- appear to have been discussed systematically with ginal problems in anatomy. However, I believe that appropriate emphasis on organs although it would the treatment of organs contains very important be devoid of its fundamental framework without the problems unavoidable in understanding the "frame- concept of organum. It may be more accurate to say work of anatomy" and exploring the ways to "recon- that anatomists have hardly intended to study organs, struct the system of anatomy" (Wakuri, 1990, 1991). including researches of organ systems, and those According to Knese (1957), terms for organs have relativities in the perspective of the entire architec- been used only in the realm of regional anatomy, and ture of the body. We are primarily interested in the no great importance seems to have been attached to organ anatomy or organology of domestic animals organs themselves in the entire discipline of anatomy. (Wakuri, 1985; Wakuri Sc, Chung, 1986; Wakuri, Nevertheless, the term organ is not necessarily 1990, 1991), but I would like here to review how out of use today. P.N.A. was revised extensively organs have been treated in contemporary anatomy. in 1965, followed by the issue of the Nomina Em- The history of the appearance of the terms for bryologica (1984), Nomina Histologica (1985), and organs in the Nomina Anatomica may be outlined General Anatomical Nomenclature (1986). Terms as follows. Organ names were included as general of organs are included in the Termini Generates of terms at least in the Basel Nomina Anatomica of these books. As above mentioned, organs are incor- the early days (Suzuki, 1941; others). However, gen- porated as general terms also in N.A.J.. eral terms for organs were omitted from the Jena Apart from these developments of the anatom- Nomina Anatomica and the Paris Nomina Anatomica ical terminology, organs have been considerably (P.N.A., 1955) (Knese, 1957). General terms for recognized in education of anatomy as demonstrated organs are incorporated in the Nomina Anatomica by the appearance of organ names in standard text- Japonica (N.A.J.). They were also seen in the Nomina books of histology (Kroening & Grau, 196); Bloom

* See a note at the end of this paper .

225 226 H. Wakuri

& Fawcett, 1969; Ogawa et al., 1988), embryology Krahmer et al (1976) and Dellmann & Brown (1987) (Patten, 1948), and macroscopic and systematic anat- described "digital organ (= organum digitale)". This omy (Krahmer et al. , 1976; Dyce et al. , 1987). There- is considered to be larger structure that are ranked fore, the organ is considered to be, so to speak, a as category of organa. traditional term. However, it is undeniable that eva- Chauveau Arloing (1873), Evans & Christen- luation of the universal morphological characteristics sen (1979), N.A. (1989), N.A.V.-N.H., N.A.J., and significance of organs still lags markedly behind. N.A. V.J. and Dyce et al. (1987) treat structures such In this paper, I would like to promote under- as the locomotory apparatus, apparatus digestorius standing of the reality that organs have diverse mor- (= digestive apparatus), apparatus respiratorius (= phological features and that they are interpreted in respiratory apparatus), apparatus urogenitalis, and a variety of ways rather than to establish definitions apparatus lacrimalis in the category of the apparatus. of organs. I will attempt a few evaluations in order Structures such as the apparatus reticulatus internus, to provide clues to formation of reasonable concepts apparatus mitoticus, apparatus fusalis, apparatus as well as information for this purpose. hyoideus, and apparatus suspensorius mammarius are mentioned in N.A. V. -N. H. , N.A.J. and N.A.V.J.. Apparatus terms of apparatus Golgi, vasomotor Examples of the Use of Organ Terminology apparatus, and juxtaglomerular apparatus are also described in the medical dictionary (Dorland, 1980) In anatomy, there are described that various and textbook of Histology (Fujita & Fujita, 1984). kinds of tissues are arranged into structure known In macroscopic anatomy or systematic anat- as organs. That is, the organ is a part of the body omy, the locomotor system (skeleton, and skeletal that is composed of one to several tissues and has muscles), cardiovascular system (blood, blood ves- an independent and definite shape and function sels, and lymphatic vessels), nervous system (central (Leach, 1961; Yoshioka & Awaya, 1969; Dorland, nervous, peripheral nervous, and autonomic ner- 1980; Nakai et al. , 1984). In general, the organ is de- vous), and endocrine system (= System der endo- fined clearly only in the field of histology (Kroelling krinen Druesen, or endocrine glands) are understood & Grau, 1960; Leach, 1961; Ogawa et al., 1988). as systems with specific functions (Ellenberger & This definition provides expression to the funda- Baum, 1943; Nickel et al., 1986; Dyce et al., 1987). mental morphology of the organ, and is the basis The apparatus digestorius, apparatus respiratorius, for its perception and understanding. Understand- and apparatus urogenitalis are respectively described ing of the organ will naturally be confused if a term also as the systema digestorium, systema respir- that is assumed to have only one meaning is inter- atorium , and systema urogenitale in N.A.J. , which preted varyingly in relation to several morphological ranks the apparatus with the systema. or structural entities. Quite unexpectedly, the ter- To force a tentative summary from the above minology for the organ has been applied to a wide mentioned examples, large structures of a systematic spectrum from macroscopic to ultrastructural levels. dimension are refered to as systemae and structures The following are randomly selected examples of of a slightly lower rank as apparatus. Organa appears the terminology of the organ used to express the to rank lower than apparatus. The expression "organ morphology or structures of the body. system" (Patt & Patt, 1969; Bloom & Fawcett, 1969; Group of the organs are considered as forming Krahmer et al. , 1976; Nickel et al. , 1986) seems to systems. These organ systems form the organism, cover the ranks of the systema, apparatus, and organa or complete animal body. First, the term organ is collectively (Table 1). However, to which rank in used to refer to a larger structure of the body which the organ system individual major structures are is made up of associated organs and performs a classified varies widely among researchers (Bloom specific task. These larger structures are expressed & Fawcett, 1969; Krahmer et al., 1976; Dorland, as "organa" in macroscopic anatomy and systematic 1980; Nickel et al., 1986) despite their definitions anatomy. They are too called as complex organ sys- in glossaries. Zietzschmann et at. (1943) describe tems (Leach, 1961) or organ systems (Abramson & to same level as Organ apparatus or Organ system. Dobrina, 1984). For example, terms such as "organa I think that "organ system" is included into category urinaria", "organa genitalia feminina", "organa of "organa" (= complex organ system). genitalia masculina", "organa genitalia feminina", Secondly, the term organ is used for structures "organa sensuum (or organa sensoria)" , "organa that are in agreement with its definition (Stoehr oculi accessoria", "organa haemopoietica", "organa Moellendorff, 1922; Leach, 1961; Yoshioka & lymphopoietica", and "organa accessoria embryo- Awaya, 1969; Dorland, 1980; Nakai et al., 1984). nalia" are observed in the N.A. (1989), N.A.V.- In this case, organ refers to structures that occupy N.H., N.A.J. and N.A.V.J.. N.A.V. (1968, 1973), particular positions and are present independently in Morphology and Terminology of the Organs 227 the body, for example, the stomach, intestines, liver, vomeronasale in the nasal cavity (especially septum pancreas, heart, lungs, kidneys, spleen and others. nasale), and organum subfornicale, organum sub- Os ut organum (= Organknochen; Kroelling & Grau, commissurale, organum vasculosum laminae ter- 1960) and glandula ut organum (= Organdruesen; minalis, and organum vasculosum hvpothalami of Kroellingg Grau, 1960) belong to this category. the diencephalon (these collectively called as cir- N.A.V.-N.H. and N.A.V.J. does not include cumventricular organs; Fujita Fujita, 1984; Ogawa organum as a general term. However, this term et al. , 1988), organum orobasale in the oral cavity, is used widely in standard textbooks of histology, organum enameleum of the dens, and organum gustus embryology, macroscopic anatomy, and systematic (or gemma gustatoria) of the tongue are seen in anatomy (Stoehr & Moellendorff, 1922; Kroelling Evans & Christensen (1979), N.A.J. , N.A.V.-N.H. & Grau, 1960; Bargmann, 1967; Bloom & Fawcett, and N.A.V.J.. These organs are of smaller telar 1969; Patten, 1948; Krahmer et al., 1976; Dyce et al., dimensions as compared with the organs that they 1987). In developmental anatomy, the early differ- are part of. entiation of the organ systems is especially empha- These small telar structures are considered to be sized (Patten, 1948). ranked appropriately as sub-organs to distinguish Single organs are classified into the three types them from organelles of cytology (Table 1). of membranous organs, hollow organs, and par- Small telar structures that would be classified as enchymatous organs and eleven subtypes according sub-organs include the insulae pancreaticae of the to their appearance and telar architectural charac- pancreas, medulla ossium in the bone, fusus neuro- teristics to facillitate their understanding (Wakuri, tendineus and fusus neuromuscularis in the skeletal 1985; Wakuri & Chung, 1986; Wakuri, 1990, 1991). muscle. (See Table 1). In general, real organs are divided into two types Fourthly, the term organ may be used on the of the hollow organs in the alimentary tracts and cytological level. The nomenclature of organellae solid organs in the glands (Chauveau & Arloing, cytoplasmicae (= cell organelle) inclusive of the 1873; Ellenberger & Baum, 1908; Bloom & Fawcett, cytocentrum, mitochondrion, complexus golgiensis, 1969; Krahmer et al., 1976; Fujita & Fujita, 1984; reticulum endoplasmicum (or cytoplasmicum), ribo- Adams, 1986). Hollow organs have morphological soma, and lysosoma is already sufficiently estab- characteristics exemplified by the canalis alimen- lished (Bargmann, 1967; Otsuki, 1979; Dorland, tarius and include all tubular structures of the body. 1980; N.A.V.-N.H.; N.A.J. ; Gotoh et al. , 1987). Parenchymatous organs have structural features Organelle (= organ-elle) is a shortened form of the represented by glandular organs and include various organ terminology. Organelle is also called cell- solid organs of the body. And membranous organs organ (Kato, 1980), micro-organ (Thorpe, 1974), include all sheet-like organs not belonging to the or organoid (Gotoh et al. , 1987). Peroxysoma, plas- above two categories. malemma, nucleus, microfibrilla, neurofilaments, Krahmer et al. (1976), N.A.V.-N.H., N.A.J. , and and microtubulus are also cell organelles in a broad N.A.V.J. rank sensory organs such as the organum sense (Jenkins, 1972; Ogawa et al. , 1988). visus (or organum visuale), organum vestibulococh- Fifthly, systems of systematic anatomy may all be leare, organum olfactus (or organum olfactorium), regarded as "organs". They are a series of associated organum vomeronasale (= Jacobson's organ), and organs (Leach, 1961). Nusshag (1938) divided anato- organum gustus (or organum gustatorium) as orga- mical components of the body into cells, organo- num (Table 1). However, the organum vestibuloc- tissues, and organs (corresponding to systems in ochleare is considered to be more appropriately the conventional terminology; note by the present classified with organa from the composite nature of author). He ranked the skeletal system, skeleto- its architecture. The organum vomeronasale in the muscular system, circulatory system (including the septum nasale and organum gustus in the tongue are systema lymphaticum), respiratory system, urinary considered to belong to the rank of sub-organs, be- system, reproductive system, integumentary system , cause anatomically they are parts of organs (Table 1). sensory system, nervous system, and digestive system Thirdly, structures primarily of the organo-histo- all as organum. logical level, i.e., small tissues (= telar structures) Sixthly, the term "organ- is used for convenience. that interpose at particular places in the organs in For example, Krahmer et al. (1976), Reynolds (1982), category 2, may also be called organs. These small and Fujimoto (1990) show instances of "organ" being telar structures often show characteristic or peculiar used in primary lymphoid organs, secondary lym- process of developmental, morphological, or fun- phoid organs, antibody-forming organs, organs ctional difference from those of the organs that of immune response, and lymphonodi of various they are parts of. For example, the organum spirale lympho-centra. organ of Corti) in the internal ear, organum N.) t.) oo

77.

I Appendix: Considerations on the morphology and terminology of the organs]

Table 1. Review of the terminology for various organs

Developmental, Gross- and Systematic Anatomy/ —— — — Organ system — —— Organogenesis, Gross anatomy and [Organo-] Histology/ Cytology/

* Expressed also as Composed of tr A sub-organ is of different * Expressed also as system (NAJ). Organo-tissue. nature from the organ that cell-organ, or it belong to. micro-organ.

Morphology and Terminology of the Organs 229

Discussion organs are a violation of the anatomical principle of "one term for one structure" as well as is a major Six categories that represent different interpret- factor that promotes the fuzziness of the concept of ations of the term "organ" or its analogues were the organ. At any rate, this variability of the ter- described above. This is considered to illustrate how minology for organs must be acknowledged. the term "organ" is applied to various structures of The anatomical terminology is intended for com- different architectural levels of the body, thus its monness of perception, and its interpretation must interpretation in a broad sense. The term "organ" as have validity and universality. Dyce et al. (1987) used in anatomy represents auch diverse morpho- mentioned: The anatomical terminology must be loigcal features and a wide spectrum of concepts precise and not ambiguous. A given structure should or significance. be referred to by a single term, and glossaries are Theobjective of anatomy is, of course, to under- available to correct any inconsistency or confusion stand the general structural composition and fun- in the use of such terms. We may as well add that ctions of the animal body. Classification of structutes N.A.V.-N.H. gives organ names to a considerable of the body into organ systems by macroscopic anat- number of structures but fails to carry general terms omy or systematic anatomy and into systema, appar- of organs. If there is any defect in the current ter- atus, or organa provides important clues to overall minology of organs, it is the absence of the organum, understanding of the body. Table 1 summarizes which is the basis of the terminology for various the relationship of these ranks. The sensory organs organs. It must be quickly incorporation in the described in the first category include the visual, organ nomenclature. equilibrium and auditory, olfactory, vomeronasal, Note: I would like to extend my heartful wishes and gustatory organs, which exist and function in- on the occasion of the 110th anniversary of the birth dependently. In addition, visual and equilibrium- of the veterinary anatomist Dr. Takejiro Osawa auditory organs are consdiered to have a composite (1881-1969), Prof. emeritus of the School of Veter- nature that justify their classification as organa rather inary Medicine, Azabu University, Japan and dedi- than single organs. Therefore, sensory organs should cate this paper to him, who was my teacher, with be ranked as apparatus. my grateful reminiscence of his guidance and instru- The term "organ" generally reminds us of a ctions in the years past. structure consisting of one or several tissues (Stoehr Moellendorff, 1922; Leach, 1961; Kroelling Grau, 1960; Yoshioka Awaya, 1969; Bloom & References Fawcett, 1969; Nakai et al., 1984). Actually, how- ever, there is no homogeneous tissue, and no organs 1) Abramson,D.I. and P.B. Dobrina: Blood Vessels and have simple structures constituted of one or several Lymphaticsin OrganSystems. Academic Press, Inc. , Orland- San Diego-San Francisco-NewYork-London-Toronto- genuine tissues. Tissues that make up organs are Montreal-Sydney-Tokyo-SaoPaulo, p. xix, 1984. organo-tissues (Fujimoto, 1990) with a composite 2) Adams, D.R.: Canine Anatomy — A SystemicStudy. architecture suitable for the make-up of rather than p. 3-7, The IowaState UniversityPress, Ames,1986. homogeneous tissues. All organo-tissues differentiate 3) Bargmann,W.: Histologicund mikroskopischeAnatomie des Menschen.6. Auflage, p. 33-42. 220-232, Georg of necessity according to the organogenic process ThiemeVerlag, Stuttgart, 1967. and are important materials directly related to the 4) Bloom,W. and D.W. Fawcett:A Textbookof Histology. composition and function of the organ. In other 9th ed., p. 30, 37-60, W. B. SaundersCo., Philadelphia- words, no tissue can exist apart from individual London-Toronto,1969. organs. In organs of the first category, small sub- 5) Chauvea,A. and S. Arloing:The ComparativeAnatomy organs that are peculiar in function and structure of the DomesticatedAnimals. Translated and edited by G. Fleming, p. 1-5, London,1873. and show different embryologic characteristics may 6) Dellmann,H.-D. and E.M. Brown:Textbook of Veterinary be distinguished (Table 1). Anatomy.3rd ed., p. 1-14, 409-415, Lea & Febiger, Organ terms are, thus, present in broad relation- Philadelphia,1987. ships from macroscopic and systematic structural 7) Dorland: Dorland's IllustratedMedical Dictionary . 25th ed., W. B. SaundersCo., Philadelphia-London-Toronto levels to micro-structures of the embryological and , 1965. In: Japanese edition, p. 150, 1305-1307, 1813. cytological level. I have a concept that organology HirokawaPublishing Co. , 1980. consist of organs (include sub-organs or telar and 8) Dyce, K.M., W.O. Sack and C.J.G, Wensing:Textbook cellular structures) or organ systems. The body of VeterinaryAnatomy. p. IX—X1,1-3, W. B. Saunders cannot exist without organs or organ systems, and Co., Philadelphia, 1987. 9) Ellenberger,W. und H. Baum: Handbuch der verglei- there will be no scientific organization of anatomy chenden Anatomicder Haustiere. 12. Auflage, p . 1-5. without the concept of the organ. This morphological Berlin,1908.. multiplicity and terminological ambiguity concerning 10) Evans, H.E., and G.C. Christensen: Miller's Anatomy. of 230 H. Wakuri

the Dog. 2nd ed., p. 148, 411, 510-511, 758, 802-863, Inc., New York-Toronto-London, 1961. 967-968, 1030-1058, 1059-1073, 1103-1105, W. B. 26) Nakai, J., K. Ooe, T. Mori, E. Yamada, N. Kanemitsu Saunders Co. , Philadelphia-London-Toronto, 1979. and T. Yoro: Anatomical Dictionary. p. 88, Asakura-shoten 11) Fujimoto, T.: The Man as a Living being, its hidden Bio- Co. Ltd., Tokyo, 1984. (in Japanese) mechanism. p. 4-13, Ishiyaku-shuppan Co. Ltd., Tokyo, 27) Nickel, N., A. Schummer, E. Sciferle, J. Frcwein, H. 1990. (in Japanese) Wilkins, and K.-H. Wille: The Locomotor System of the 12) Fujita, H. and T. Fujita: Textbook of Histology. Part 2. Domestic Animals. Vol. 1, Translation by Walter, G.S. 2nd ed., p. 72-73, 199, Igaku-shoin Co. Ltd., Tokyo, 1984. & W.M. Stokoe, p. 3-5, Verlag Paul Parey, Berlin & (in Japanese) Hamburg, 1986. 13) Gotoh, S. et al.: Ishiyaku-Shuppan's Medical Dictionary. 28) Nusshag, W.: Lehrbuch der Anatomic und Physiologic p. 523, Ishiyaku Publishers Inc., 1987. der Haustiere. p. 9-12, 41-44, 343, S. Hirzel Verlag 14) International Anatomical Nomenclature Committee: Leipzig, 1968. Nomina Anatomica (N.A.). 6th ed., p. H7—H8, H35—H38, 29) Ogawa, K., A. Suzuki, M. Kiotera, T. Nagano, K. Hashi- Chirchill Livingstone, Edinburgh, 1989. moto, M. Hashimoto, E. Yamada, T. Yamamoto and 15) International Committee on Veterinary Anatomical Nomen- Y. Watanabe: The Human Histology. Vol. 1, p. 3-38, clature: Nomina Anatomica Veterinaria (N.A.V.). P. VII— Asakura-shoten Co. Ltd., Tokyo, 1988. (in Japanese) IX, 296, 142, World Association of Veterinary Anatomists. 30) Patt, D.I. and G.R. Patt: Comparative Vertebrate Histo- Vinna, 1968. logy. p. 19-20, Harper & Row, Publishers, New York- 16) International Committee on Veterinary Anatomical Nomen- Evanston-London, 1969. clature: Nomina Anatomica Veterinaria (N.A.V.). 2nd 31) Patten, WM.: Embryology of the Pig. p. 1-5, McGraw- ed., with Index, P. VII—X, 2-6, 146, World Association Hill Book Co., New York, 1948. of Veterinary Anatomists. Vinna, 1973. 32) Reynolds, G.J.: Lymphoid Tissue. A Histological Ap- 17) International Committee on Veterinary Gross Anatomical proach. p. 1-14, John Wright & Sons. Ltd., Bristol-London- Nomenclature: Nomina Anatomica Veterinaria. 3rd., Boston, 1982. together with Nomina Histologuca (N.A.V.-N.H.). P. 33) Smollich, A. und G. Michel: Mikroskopische Anatomic A1—A4, A10—Al2, H3—H5, H9, H15, World Association der Haustiere. p. 11-12, 156-158, VEB Gustav Fischer of Veterinary Anatomists, Ithaca, New York, 1983. Verlag, Jene, 1985. 18) Japanese Association of Anatomists: Nomina Anatomica 34) Stoehr, P. and W. Moellendorff: Lehrbuch der Histologie Japonica (N.A.J.). Revised 12th ed., P. 3, 11, 79, 93, und der Mikroskopischen Anatomie des Menschen mit 102-104, 148-196, 201-210, Maruzen Co. Ltd., 1987. einschluss der Mikroskopischen Technik. 19. Auflage, p. (in Japanese) 157-158, Verlag von Gustav Fischer, Jena, 1922. 19) Japanese Association of Veterinary Anatomists: Nomina 35) Suzuki, B.: Nomina Anatomica (N.A.). Revised 17th ed., Anatomica Veterinaria Japonica (N.A.V.J.). Revised p. 7, Maruzen Co. Ltd., Tokyo, 1932. (in Japanese) 3rd ed., P. 26, 44, 105-127, 138-148, 254-263, 280-291, 36) Thorpo, W.H.: Animal Nature and Human Nature. p. 17, 305, 356, Nippon-chuo-keibakai-kosaikai. Tokyo, 1987. Anchor Press, Doubleday, New York, 1974. (in Japanese) 37) Wakuri, H.: Organology of the domestic animals. Why 20) Jenkins, T.W.: Functional Mammalian Neuroanatomy. with research the organs. J. Vet. Med. (Tokyo). No. 769: 479— emphasis on dog and cat, including an atlas of dog central 482, 1985. (in Japanese) nervous system. P. 47-49, Lea & Febiger, Philadelphia, 1972. 38) Wakuri, H. and U.Y. Chung: The organology of the do- 21) Kato, K.: Kato's Integrated English-Japanese Medical mestic animals. J. Korean Vet. Med. Assoc., 22: 567-572, Dictionary. P. 1096-1097, Nanzando Co. Ltd., Tokyo, 1986. (in Korean) 1980. (in Japanese) 39) Wakuri, H.: New concepts and prospects for unity of anat- 22) Knese, K.-H.: Kopsch's Nomina Anatomica. Vergleichende omy. Kitasato Arch. of Exp. Med. , 63: 185-192, 1990. Uebersicht der Basler, Jenaer und Pariser Nomenclatur. 40) Wakuri, H.: The Comprehensive Anatomy of the Domestic 5. Auflage, p. VII—XI, 4, 82-83, 129, George Thieme Animals. Chikusan-shuppansha Co. Ltd., Tokyo, 1991. Verlag, Stuuttgart, 1957. (in Japanese) 23) Krahmer, R.. L. Schroeder und G. Michel: Anatomie der 41) Yoshioka, S. and K. Awaya: Anatomical Terms. Their Haustiere. p. 15-19, 140-142, 229, 269-277, S. Hirzel Origin, Construction and Pronunciation. p. 113, 137, 215, Verlag, Leipzig, 1976. Igaku-shoin Co. Ltd., Tokyo, 1969. (in Japanese) 24) Kroelling, 0. und H. Grau: Lehrbuch der Histologie und 42) Zietzschmann, 0., E. Ackerknecht und H. Grau: Ellen- vergleichenden Mikroskopischen Anatomie der Haustiere. berger-Baum's Handbuch der vergleichenden Anatomic der Hausticre, 18. Auflage, p. 1-3, Springer-Verlage p. 37, 67, 191, Paul Parey in Berlin und Hamburg, 1960. 25) Leach, J.: Functional Anatomy — Mammalian and Com- Berlin, 1943. parative. 3rd ed., p. 1-5, 20-38, McGraw-Hill Book Co.,