EABBIT. 137 



as long as possible] except those connected with 

 the lungs. Take out heart and lungs and put 

 them into a dish of ivater. 



1. Identify again the vessels entering and leav- 



ing the heart. 



Cut aivay the outer walls of both auricles and wash 

 out the Hood. 



2. See the septum with the fossa ovalis, and the 



entering veins. 



Make with fine scissors a cut through the ventral 

 wall of the pulmonary artery and continue it 

 through the wall of the right ventricle. 



Note : 



3. The auriculo-ventricular (tricuspid) valve. 



4. The ventricular septum. 



5. The semilunar valves at the base of the 



pulmonary artery. 



6. Cut away the outer wall of the left ventricle 



and compare its thickness with that of the 

 right ventricle. 

 Note in the left ventricle : 



7. The auriculo-ventricular (mitral) valve. 



8. The chordae tendinese. 



9. The papillary muscles. 



10. Compare 7, 8, and 9 with the corresponding 



structures in the right ventricle. 

 Note : 



11. The semilunar valves at the beginning of the 



aortic arch. 



