THE HEART AND ITS DISSECTION 



123 



The student, having provided himself with a sharp knife with a pointed 

 blade, a few wood skewers, and a jug of water, may now proceed with the 

 examination and dissection of the heart as follows : 



Place the point of the knife just underneath the surface of the heart, so as 

 to raise a portion of the very thin membrane or skin which closely invests it. 

 This membrane is the inner layer of the pericardium, the outer layer of which, 

 it will be remembered, surrounds the heart loosely, and is cut or torn away in 

 removing the organ from the chest. A few remaining portions of this outer 



Fig. 114. The Sheep's Heart, 

 viewed from before. 



i, right ventricle ; 2, left ventricle ; 

 3,' right auricle ; 4, left auricle ; 

 5, the aorta ; 6, a cut branch of the 

 aorta ; 7, pulmonary artery. To open 

 the right ventricle, cut as shown by 

 the thick unbroken line. To orjen 

 the left ventricle, cut along the thick 



fine's! feJSSUJfflSS, Fig. i i 5 .-The Human Heart and its 



vessel, marking the position of the Vessels, viewed from before. 



septum which separates the ventri- ^ righ( . vmtMe . a> , eft ventricle . 3| * of 



the pulmonary artery cut short ; 4, 4', and 

 4", the aorta ; 5, right auricle ; 6, left auri- 

 cle ; 7, veins which unite to form the vena 

 cava superior ; 8, inferior vena cava ; 9, he- 

 patic vein ; + , coronary arteries. 



layer may still be seen attached to the great blood-vessels at the base of the 

 heart, for it is here that the inner adherent layer is reflected back to form the 

 outer and loose layer. 



Now notice the two thin fleshy flaps which lie over the base of the heart 

 like ears, one on each side. These are the auricles (Lat. auricula, a little 

 ear). They are hollow, and, of course, when distended with blood, do not 

 lie so flat. Notice also the general conical shaoe of the heart. 



