UROGENITAL SYSTEM OF THE FROG 1 



1. Pin the specimen 2 — from which you have previously removed the 

 alimentary canal and associated organs — in a dissecting pan, ventral sur- 

 face up as before. Carefully cut through the bony pelvis in the median 

 line and thus completely expose the cloaca, into which the rectum and the 

 ducts from the urinary and genital organs empty, and, on the ventral sur- 

 face of which, the thin-walled, bilobed bladder opens. 



2. Female Frog. In the spring, the right and left ovaries become 

 greatly distended and fill a large portion of the body cavity. Separate the 

 ovaries and push them to either side so that the other organs may be seen 

 to advantage. Note : (a) a pair of reddish, flattened, oval-shaped kid- 

 neys, close to the dorsal body wall ; (b) a pair of elongated, orange-colored 

 adrenal bodies, one lying on the ventral surface of each kidney ; (c) a 

 pair of yellowish fat bodies with long finger-like processes ; (d) a pair of 

 long, coiled oviducts which open anteriorly into the body cavity near the 

 base of each lung. Posteriorly, before opening into the cloaca, each of the 

 oviducts enlarges to form (e) a thin-walled uterus. Examine the outer 

 margin of the kidneys and find on each (/) a ureter, which can be traced 

 posteriorly to its opening in the cloaca. Note also the blood vessels 

 which supply the kidneys. Make an enlarged drawing to show the struc- 

 tures observed. 



3. Male Frog. Locate and examine the following parts of the male 

 urogenital system : (a) a pair of reddish, flattened, oval-shaped kidneys, 

 close to the dorsal body wall ; (b) a pair of white testes attached to the 

 kidneys by a number of fine ducts (vasa efferentia) ; (c) a pair of elon- 

 gated, orange-colored adrenal bodies, one lying on the ventral surface of 

 each kidney; (d) a pair of yellowish fat bodies with long finger-like 

 processes; (e) in many specimens a pair of small, coiled rudimentary 

 oviducts are to be found situated laterally to the kidneys. Examine the 

 outer margin of the kidneys and find (f) the urogenital canals, each 

 of which can be traced posteriorly to its opening in the cloaca. Note also 

 the blood vessels attached to the kidneys. Make an enlarged drawing to 

 show the structures observed. 



1 B. pp. 204-206. 



2 Better results will be obtained by using a fresh specimen for this exercise 



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