130 



STUDIES IN PHYSIOLOGY 



P.K 



downward toward the left side, the fist will represent ap- 

 proximately the size, shape, and position of the heart. To 

 be more exact, one may describe the heart of an adult as 



a conical organ, 

 IX*. five inches in 

 length. It lies 

 diagonally be- 

 hind the breast- 

 bone, near the 

 middle of the 

 chest cavity, 

 with its pointed 

 end or apex ex- 

 tending toward 

 the left side be- 

 tween the fifth 

 and sixth ribs. 

 Since the beat 

 of the heart is 

 felt most plainly 

 near the apex, 

 it is commonly 

 but erroneously 

 believed that 

 the heart lies 

 on the left side 

 of the body. 

 Let one imagine 

 the front wall 

 of the chest cav- 

 ity to be re- 

 moved; one 



FIG. 47. Ventral View of Heart, Large Blood Ves- 

 sels and lungs. 



Ao = aorta curving toward left. 

 B = bronchi to lungs. 

 (7= carotid arteries. 

 L.A. = left auricle. 

 L.J.V. = left jugular vein. 

 L.L = left lung. 

 L. V= left ventricle. 



P. A = pulmonary artery dividing into two. 

 P. V= pulmonary veins. 

 R.A = right auricle. 

 R.J.V= right jugular vein. 

 R.L = right lung. 

 R. V right ventricle. 

 S.C. = arteries and veins supplying shoulders and 



arms. 



T trachea or windpipe. 

 V.l = inferior vena cava. 

 V.S = superior vena cava. 



would then see 

 the soft, pink lungs on either side, nearly filling the chest 

 cavity, and between them the heart (see Figs. 4 and 47). 

 The Pericardium. The heart is not only surrounded by the 



