RENAL AND BEPRODUCTIVE SYSTEMS 335 



ii. The colunmse carneae are muscular ridges pro- 

 jecting into the cavity of the ventricle, and 

 mainly longitudinal in direction. 



iii. The orifice of the aorta is at the base of the 

 ventricle, immediately to the right of the 

 mitral valve. It is guarded by three semilunar 

 valves, one of which is dorsal, and the other 

 two ventro-lateral in position. Immediately 

 beyond the two latter valves the coronary 

 arteries, which supply the heart, arise from 

 the aorta. 



VII. DISSECTION OF THE RENAL AND REPRODUCTIVE 

 SYSTEMS. 



In the rabbit, as in the dog-fish, certain parts of the primi- 

 tive kidneys and their ducts lose their excretory function, and 

 become converted into accessory genital organs and genital 

 ducts. Owing to the close connection of the two systems, they 

 may, in the adult, be conveniently considered together, though 

 it must be remembered that the connection is merely a 

 secondary one (c/. pp. 238-239). 



In the male rabbit, of the three divisions into which the 

 primitive kidney is divided, the pronephros and its duct are 

 absent or rudimentary ; the mesonephros acquires an intimate 

 connection with the testis, and becomes converted into the 

 epididymis, its duct becoming the vas deferens. 



In the female, the pronephros is absent, but its duct 

 becomes the oviduct ; the mesonephros and its duct are 

 absent, or rudimentary. 



In both sexes alike, the metanephros and its duct become 

 the kidney and ureter respectively. 



The bladder of the rabbit arises as a ventral diverticulum 

 of the rectum, and is at first entirely independent of the 

 kidney-ducts, which open into the dorsal wall of the rectum, 

 a condition retained throughout life in the frog. During 

 development the ducts shift round so as to open into the 

 bladder, which then separates from the rectum and acquires 



