12 THE FROG 



(b) The kidneys, or excretory organs, have been identified behind 

 the peritoneum of the dorsal wall of the ccelom. Carefully remove 

 the right oviduct and completely expose the kidneys. The ureter is 

 a slender, light-colored duct, arising from the outer edge of each 

 kidney near its posterior end and extending backward to the cloaca. 

 It conveys the urine from the kidney to the cloaca. Do not confuse 

 the ureter with the several large, white nerves on the body wall dorsal 

 to the ureters, or with the large, dark-colored blood vessel which 

 enters each kidney close to its ureter. Difficulty in locating and 

 tracing the ureter arises from the fact that it is attached to the 

 dorsal surface of the expanded portion of the oviduct. The ureter 

 is, however, entirely distinct from the oviduct; each oviduct and 

 each ureter opens separately on the dorsal wall of the cloaca. Be 

 prepared to demonstrate your dissection to the instructor and to 

 explain the dorso-ventral relationships of the parts. Make a draw- 

 ing (X 3 or 4) of the female urino-genital organs, including the 

 cloaca and the bladder, as seen from the ventral aspect. It may be 

 well to show only one of the oviducts. Indicate in this drawing the 

 size and position of one ovary by a dotted outline. Be very careful 

 to show accurately the relationship of ureters, oviducts, bladder, and 

 cloaca. Examine a dissection of the urino-genital system of a male 

 frog. Now take up the work of Exercise 13. 



Exercise 12. — The Male Urino-genital System. 



(c) The kidneys, or excretory organs, have been identified behind 

 the peritoneum of the dorsal wall of the ccelom. The testes, which are 

 the reproductive organs or gonads of the male, are a pair of small, 

 elongated, light-colored bodies suspended from the anterior end of the 

 kidneys. The mesentery that supports each testis is called a mesor- 

 chium. 



(d) Running along the outer margin of each kidney is a slender, 

 coiled structure, the rudimentary oviduct, which corresponds to the 

 oviduct of the female, but is not functional in the male. These rudi- 

 mentary oviducts expand at their posterior ends and connect with the 

 dorsal wall of the cloaca opposite the place of attachment of the 

 bladder, in the same manner as the functional oviducts of the female. 



(e) The ureter is a slender, light-colored duct, arising from the 

 outer edge of each kidney near its posterior end and extending back- 

 ward to the cloaca. It conveys the urine from the kidney to the 

 cloaca. Do not confuse the ureter with several large, white nerve 

 cords on the body wall dorsal to the ureters, or with a large, dark- 

 colored blood vessel which enters each kidney close to its ureter. 



