COMPARATIVE ANATOMY OF THE UROGENITAL SYSTEM 287 



various sizes, situated at the anterior end of the left kidney. It is attached by 

 a, short mesovarium. Posterior to the ovary the coiled left oviduct proceeds to 

 the cloaca, being supported by the mesotubarium. ' The ostium is situated in 

 the mesotubarium near the ovary; it is a wide opening with winglike borders 

 fastened to the mesotubarium. A small remnant of the right oviduct is attached 

 to the right side of the cloaca. 



The kidneys are metanephroi. Each is a flattened, three-lobed organ situated 

 against the dorsal wall. The ureters or metanephric ducts are located just dorsal 

 to the renal portal veins which should be stripped from the face of the kidney. 

 The ureter begins on each side at the groove between the anterior and middle 

 lobes of the kidney and extends straight posteriorly to the cloaca. The left 

 ureter is concealed by the oviduct. 



The cloaca is an expanded chamber receiving the rectum on its median 

 ventral surface, the left oviduct to the left, the very small right oviduct to the 

 right, and the ureters dorsal to the oviducts. Cut into the cloaca to the right 

 of the rectum. Note that the cavity of the cloaca is subdivided. There 

 is a large ventral portion (coprodaeum) into which the rectum opens. Dor- 

 sal to this and separated from it by a fold is the urodaeum into which open 

 the oviducts and ureters. The opening of the left oviduct is readily found here; 

 the openings of the ureters are more medial and smaller. The most dorsal 

 compartment of the cloaca is the proctodaeum, a small chamber with a raised 

 rim, which opens to the anus. In the anterior wall of the proctodaeum dorsal 

 to the rim an opening may be noted; it leads into a small pouch which seems to 

 be functional in young birds but degenerates with maturity. It is called the 

 bursa of Fabricius. 



Draw urogenital system and cloaca. 



2. The male urogenital system. — The testes are a pair of oval organs at the 

 anterior ends of the kidneys; their size varies considerably with the season. 

 The kidneys are the same as in the female, and the description given under the 

 female should be read and the ureters identified. The male ducts, vasa deferentia 

 (Wolffian ducts), spring from the medial border near the posterior end of the 

 testes and pass posteriorly parallel to the ureters. They are slender convoluted 

 tubes. Trace both ureters and vasa deferentia to the cloaca. 



The cloaca is smaller than in the female and the lips of the anus more protrud- 

 ing. The rectum enters medially and ventrally, the urogenital ducts laterally. 

 Cut into the cloaca as directed under female and identify its chambers as there 

 described. They are the same in the two sexes, except that the urodaeum is 

 smaller and receives the two vasa deferentia instead of the oviduct. Ureters 

 and vasa deferentia open on small papillae in the lateral walls of the urodaeum. 

 There is no penis in most birds. 



Draw. 



