Title: Elements of comparative anatomy
Identifier: elementsofcompar00gege (find matches)
Year: 1878 (1870s)
Authors: Gegenbaur, C. (Carl), 1826-1903; Bell, F. J. (Francis Jeffrey), 1855-1924; Lankester, E. Ray (Edwin Ray), Sir, 1847-1929
Subjects: Anatomy, Comparative
Publisher: London, Macmillan and Co.
Contributing Library: MBLWHOI Library
Digitizing Sponsor: MBLWHOI Library

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G18 COMPARATIVE ANATOMY. The apparatus thus formed is variously modified in different parts. The testes do not retain their primitive position anteriorly to the kidneys in any Mammals except the Monotremata. In the Cetacea, Hyrax, Elephas, and various Edentata, they are placed a little to the side of, or below the kidneys. In others they are found in the inguinal region of the ab- dominal wall, which they pass through (many Rodents, the Camelida3, and various Car- nivora (Lutra, Viverra)). In others, finally, they travel still further by means of the ingui- nal canal, descending through the wall of the abdomen iuto a diverticulum, the scrotum, which is formed from the in- tegument. The space which is formed (canalis vaginalis) when the testis passes into the scro- tum, by the peritoneum which grows out with the descending testis, is permanently open in most Mammals, so that the cavity around the testis is in communication with the ab- dominal cavity. As the testes pass down the inguinal canal the abdominal wall is driven in front of them. When the vaginal canal remains open the testes may return again to the abdominal cavity; this ordinarily happens in many Mammals during the breeding season (e.g. Marsupialia, Ro- dentia, Chiroptera, Insectivora, etc.). The scrotum of the Marsupialia is remarkable for its position in front of the genital orifice. It is a special structure, while in the Mono- delphia the scrotum is de- veloped from the boundary of the primitive urogenital orifice. The lower end of the vas deferens is always simple in the Monotremata and Marsupialia, Carnivora and Cetacea. In the rest it gives rise to glandular structures, which are known as "vesiculas seminales," as the sperm may be collected in them (yl). These organs are greatly develoj^ed in the Insectivora and many Rodents;
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Fig. 353. I Urinary and generative organs of Cricetus vulgaris. B Kidneys. u Ureter, v Urinary bladder. T Testes. Sp Vasa spermatica. il Vas deferens, gl Vesicular seminales. gV gl" Prostatic glands. m Muscular portion of the urogenital sinus. ic Corpus cavernosum penis, be Corp. cav. urethras. c Cowper's glands. t Tyson's glands, p Prepuce, g Glans penis. II Neck of the bladder, and commencement of the urogenital sinus, opened in front. * Opening of the ductus ejaculatorii. Ill Glans penis seen from in front.

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