THE HEART 



555 



left than into the right half of the thoracic cavity, so that about one-third of it is 

 situated on the right and about two-thirds on the left of the mesal plane. 



Size and Weight. The normal heart, in the adult, measures five inches in 

 length, three inches and a half in breadth at the broadest part, and two inches and 

 a half in thickness. The prevalent weight, in the male, varies from ten to twelve 

 ounces (average, eleven ounces); in the female, from eight to ten; its proportions 

 to the body being as 1 to 160 in males; 1 to 150 in females. The heart continues 

 to increase in weight and in size up to an advanced period of life; this increase is 

 more marked in men than in women. 



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FIG. 414. Position of the heart. The pericardium laid open. Adult male. (Poirier and Charpy.) 



Configuration. The heart is subdivided by a muscular septum into two 

 lateral halves, which are named, respectively, the right or pulmonary heart and the 

 left or systemic heart; and a transverse constriction subdivides each half of the organ 

 into two cavities, the dorsal cavity on each side being called the auricle; the ventral, 

 the ventricle. The heart, therefore, consists of four chambers viz., the right and 

 left auricles, and right and left ventricles. The course of the blood through the 

 heart cavities and bloodvessels has already been described ( page 549). 



The division of the heart into four cavities is indicated upon its surface by 

 grooves. The groove separating the auricles from the ventricles is called the 



