334 DISSECTION OF THE RABBIT 



The cavity of the right ventricle is crescentic in 

 section: its wall is thin, embracing and half-sur- 

 rounding the left ventricle. 



The left ventricle has very thick walls, and a 

 small irregular cavity. 



a. The right ventricle. 



Bemove the auricles, and cut short the aorta and pul- 

 monary artery. Bemove the outer wall of the right ventricle, 

 by longitudinal incisions through its dorsal and ventral walls, 

 and a transverse incision across its base a short distance 

 behind the anterior border. Avoid injury to the valve. 



i. The tricuspid valve guards the right auriculo- 

 ventricular aperture, and is formed by three 

 membranous flaps attached round its margin. 

 The free borders of the flaps project into 

 the ventricle, and are connected by tendinous 

 strings, the chordae tendinese, to muscular 

 processes of the wall of the ventricle, the 

 larger of which are known as musculi papil- 

 lares. 



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. 



