154 



UNCONSCIOUS NERVOUS OPERATIONS 



apex points downward ai}d forward a little to the left of 

 the sternum, or breastbone. The heart is divided longitu- 

 dinally irito two divisions wholly separate from each other. 

 Each of these is divided again into two chambers which 

 have free communication. The chambers at the base 



Left Pulmonary 

 Artery 



..Left Auricle 



Fig. 87. Front view of heart. 

 Coronary arteries and veins are injected, arteries red, veins blue. 



of the cone are called the right and left auricles, while 

 the other two are called right and left ventricles (Figs. 87 

 and 88). Lying upon the outside of the auricles are two 

 flat earlike structures which are called the right and left 

 appendi'ces. 



213. The Eight Auricle lies on the right side of the upper 

 part of the lieart. Its walls are thin, and are pierced by 

 openings for the two great veins, the superior vena cava. 



