THE UROGENITAL ORGANS. 



or larynx, is placed at the lower end of the pharynx, behind the root 

 of the tongue ; it is supported by the posterior horns of the hyoid 

 bone, possesses lower vocal cords, complicated pieces of cartilage 

 (cricoid, thyroid, and arytenoid cartilages) and muscles, and co:.-,f- 

 tutes a vocal organ. 



In the Cetacea alone is the larynx, which projects in the base of the 

 pharynx as far as the posterior nares, used exclusively for respira- 

 tion. A movable epiglottis (almost tubular in the Cetacea}, attached 

 to the upper edge of the thyroid cartilage, projects over the glottis. 

 When food is being swallowed it sinks, and closes the glottis. Acces- 

 sorv cavities, with membranous or cartilaginous walls, are sometimes 

 attached to the larynx. These sometimes function as air reservoirs, 

 e.g., the air-sacs of Balwna, sometimes as a resonating apparatus for 

 the strengthening of the voice, as in many Monkeys (Mycetes). 



The kidneys (fig. 677) still sometimes consist (Seals, Dolphins) of 

 numerous lobes united together at the pelvis of the kidney. As a 

 rule, however, they are compact bean-shaped glands, lying in the 

 lumbar region, outside the peritoneum. The ureters arise from the 

 so-called pelvis of the kidney, and always open into a urinary bladder, 

 placed in front of (ventral to) the intestine. The duct of the 

 bladder, or urethra, enters into a more or less close relation with the 

 ducts of the generative organs, and leads into a sinus or urogenitcd 

 1'iiii.al opening in front of the anus. Above the kidney there is a 

 glandular organ termed the suprarenal bo/If/. 



The male sexual organs (fig. 677) of most Mammalia are 

 characterised by the change in the position of the testes. In the 

 Monotremata and Cetacea alone do the testes remain in their original 

 position near the kidneys, in all other cases they descend in front of 

 the pelvis, and, pushing the peritoneum before them, enter the 

 inguinal canal (many Rodents), or, still more frequently, pass through 

 the inguinal canal into a double cutaneous fold, which is transformed 

 into the scrotum. Not unfrequently (Rodents, Bats, Insectivores) 

 they pass back through the open inguinal canal into the abdominal 

 cavity after the breeding season : this is effected by the cremaster, a 

 slip of muscle separated from the oblique abdominal muscle. The 

 scrotum, as a rule, lies behind the penis; but in the Marsupials 

 it is formed by an invagination of the integument directly at the 

 entrance of the inguinal canal in front of the male copulatory organ. 

 The coiled excretory ducts of the testes, which are derived from the 

 Wolffian body, constitute the epi<li'lt/ni(s, and lead into the two w/.w 

 erentia, which, after forming glandular dilatations (seminal vc>i- 



