102 



THE HEART. 



blood, while its veins carry arterial blood nothing of the 

 kind being found in any other arteries or veins of the 

 adult body. In the foetus, however, the umbilical vein 

 carries red blood, and the internal iliac arteries black, but 

 these after birth become obliterated. 



The Heart is the centre of 

 the general and pulmonary 

 circulations. It is situated in 

 the middle mediastinum, be- 

 tween the lungs and behind 

 the sternum. Its form is that 

 of a cone, the apex being at the 

 junction of the fifth rib and 

 its cartilage on the left, the 

 base above and obliquely to 

 the right. It is a hollow mus- 

 cle, having four cavities, two 

 auricles, and two ventricles. 

 The auricles are above, and 

 form the base. The ventricles 

 are below, and compose the 

 body and apex. The heart, after birth, is duplicate, and 

 consists of two hearts, right and left. (Fig. 11.) 



The right heart, composed of the right auricle and ven- 

 tricle, contains venous blood; the left, consisting of the 

 left auricle and ventricle, has arterial. The right heart 

 receives the trunks of the venous tree. The left gives off 

 the trunk of the arterial tree. It is enclosed in a strong 

 fibrous capsule, which connects it below with the dia- 

 phragm, and above with the great blood vessels arising 

 from its superior portion. Its interior has valves to pre- 

 vent the blood from retrograding. There are two sets, one 

 to each heart. The right heart has, at the ostium veno- 



FIG. 10 represents an anterior view of the heart in a vertical position. 

 a Base. 6 Body and right ventricle, c Apex, d Pulmonary artery, e Right 

 auricle. / Superior cava. g Anterior coronary artery, h Left ventricle. 

 i Left auricle, j Aorta, k Arteria innominata. I Common carotid, nt 

 Left subclavian. 



