POSITION OF HEART. 



453 



the chest. 



a half in width, and two and a half in thickness. Its weight is 

 generally from ten to twelve ounces in the male, and from eight to 

 ten in the female. 



Position and direction. The heart lies behind the body of the Situation in 

 sternum, and projects on each side of that bone, but more to the 

 left than the right. Its axis is directed very obliquely, from 

 behind forwards and to the left, as well as somewhat downwards. 

 The base, or posterior surface, is towards the spine, being opposite Base ; 

 the sixth, seventh and eighth dorsal vertebrae, and looks backwards 

 and upwards. The apex strikes the wall of the chest during life in apex ; 

 the fifth intercostal space of the left side, opposite the junction of the 

 ribs with their cartilages. The anterior surface looks forwards and surfaces ; 



Duetus arteriosus. 



Branches of the pulmonary 

 artery. 



Pulmonary vein. 

 Pulmonary vein. _ 



Coronary .sinus. 



Left subclavian. 

 Left common carotid. 

 Innominate artery. 



Aorta. 



Superior vena cava. 

 Pulmonary vein. 



Pulmonary vein. 



Inferior vena caval 

 entrance to right 

 auricle. 



Right auriculo- 

 ventricular groove. 



Posterior inter-ventricular groove. 



FIG. 165. THE HEART SEEN FROM BEHIND AND BELOW. 

 (From a specimen in Charing Cross Hospital Museum). 



somewhat upwards ; while the inferior surface is nearly horizontal, 

 resting on the diaphragm. The right margin is turned to the borders; 

 front ; and the left is placed farther back. 



Inconsequence of the oblique position of the heart, the right rieht and 

 half and the apex are directed towards the thoracic wall, though 

 mostly with lung intervening ; while the left half is undermost 

 and deep in the cavity. 



Surface marling (fig. 166). The extent of the heart in relation Extent of 

 to the front of the chest may be indicated as follows : The upper 

 limit is marked by a line across the sternum from the lower edge 

 of the second costal cartilage of the left side to the upper edge of 

 the third cartilage of the right side ; and the lower limit by a line, 



