324 DISSECTION OF THE BABBIT 



b, The left ventricle, 



Remove the outer wall in the same manner as that of the 

 right ventricle. 



i. The mitral valve, guarding the left auriculo- 

 ventricular aperture, resembles the tricuspid 

 valve, except that there are only two flaps, 

 and the musculi papillares are much larger. 



ii. The columnse carnese 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 seinilunar 

 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 URINARY 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,m the adult, be conveniently considered together, though 

 it must be remembered that the connection is merely a 

 secondary one (cf. pp. 233-34). 



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. 



