352 DISSECTION OF THE RABBIT. 



ii. The orifice of the pulmonary artery is at the 



left anterior angle of the ventricle, and is 

 guarded by three pocket-like semilunar valves, 

 the free edges of which are directed away 

 from the ventricle. 



Note the position of the valves from above; sUt up the 

 pulmonary artery between two of them, and examine them. 



b. The left ventricle. 



Bemove 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 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. 



The heart of a sheep may be dissected with advantage, 

 and it differs so little from that of the rabbit, that the fore- 

 going description appUes, with very httle modification, to it. 

 The chief differences are the union of the two anterior vense 

 cavsB before entering the auricle, and the presence of a muscu- 

 lar ' moderator ' band crossing the cavity of the right ventricle 

 obUquely. 



VI. DISSECTION OP 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 



