10 GUIDES FOR VERTEBRATE DISSECTION 



therefore must serve for ureter as well as for vas deferens; in 

 other words it is urogenital in function. 



Cut through the pelvis and trace the posterior end of the 

 alimentary canal and urogenital ducts. That part into which 

 the ducts empty is the cloaca. On its ventral side is a thin- 

 walled urinary bladder. Inflate through the vent and notice its 

 shape. Beginning at the vent split the cloaca a little to one 

 side of the mid-ventral line; lay open and find the opening of 

 the urinary bladder, and in the sides the openings of Leydig's 

 ducts. 



In the female the much lobulated ovary occupies a position 

 comparable to that of the testis in the male. It is attached to 

 the peritoneal wall by a membrane, the mesovarium. Notice 

 through the ovarian walls the eggs of various sizes. Make a 

 slight incision in the wall of the ovary and inflate, noting that 

 the organ is saccular. What relations do the ova bear to its wall? 

 Also note the ovarian arteries going from the dorsal aorta to the 

 ovary. 



Dorsal to the ovary is a long convoluted tube, the oviduct 

 (Mullerian duct); trace it forward and back. Cut into it near 

 its anterior end. Note that it opens directly into the body 

 cavity in front (ostium tubae). Trace it also into the cloaca, 

 inflating and cutting if necessary. In the posterior part of the 

 coelom between the oviduct and the middle line is the meso- 

 nephros. Do you find vasa efferentia similar to those in the 

 male? Notice on the lateral margin of the mesonephros a 

 delicate tube, the ureter (Wolffian duct). Trace it backwards: 

 does it unite with the oviduct or does it open separately into the 

 cloaca? 



What is the most marked difference between the urogenital 

 ducts in the two sexes? 



Draw the urogenital system of both sexes, bringing out the 

 points discovered. 



Posterior Circulation. Follow the postcava backward from 

 the point of its connection with the postcardinals, sketching this 

 part us well as the renal and genital veins which it receives. 



Cut through the pelvis and BOO, "ii cither side of the hinder 

 part of the coelom, an iliac artery which soon divides, one branch 

 (femoral artery) passing into the hind limb, the other passing to the 

 ventral side of the body, where it forms a hypogastric artery, 



