LESSON XV. HEART OF MAMMAL. 

 Dissection of the Sheep's Heart 1 . 



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 re- 

 moval. The front of the heart may be recognised by a 

 groove filled with fat, the interventricular soilcus, 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 back. 

 Holding the heart with the front toAvards 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. 



2. Tie a short glass tube into the superior vena cava 

 and connect with it a piece of india-rubber tubing. Liga- 

 ture the inferior vena cava and the left vena azygos 

 which opens close beside it. Tie a glass tube about two 

 feet in length into the pulmonary artery. Fill the india- 

 rubber tubing with water, and squeezing it press the 



1 The heart should be obtained from the butcher with the pericardium; 

 to secure this it is advisable to purchase the 'bag,' i.e. the heart with the 

 lungs still attached to it. 



