LESSON XIII, 

 STRUCTUEE AND ACTION OF THE HEART. 



A. Heaet of Sheep*. 



1. Observe the attachment of the parietal pericar- 

 dium to the roots of the great vessels. 

 Remember that the parts of the heart which are 

 right and left in the body are called right and 

 left after removal. The front of the heart may 

 be recognized by a groove filled with fat, the 

 interventricular sulcus, which runs from about 

 the middle of the base of the ventricles to rather 

 below the middle of the right margin of the 

 heart. The front is also more convex than the 

 bacL Holding the heart with the front towards 

 you, note that the right ventricle, which will be 

 on your left hand, is much more yielding than 

 the left ventricle, which will be on your right 

 hand. Note also the pulmonary artery arising 

 nearly in the middle line of the heart at the 

 upper part of the ventricles, and immediately 

 behind this the aorta. 



' The heart should be obtained from the butcher with the 

 perlcaidium ; to secure this it is advisable to purchase the ' bag,' 

 i.e. the heart with the lungs still attached to it. 



