THE HEART 



557 



overlapped by the left lung and pleura; it lies behind the fifth left intercostal 

 space, three and a quarter inches (8 cm.) from the mid-sternal line, or about 

 an inch and a half (4 cm.) below and three-quarters of an inch (2 cm.) to the 

 inner side of the left nipple in the male. The apex is wholly made up of the left 

 ventricle. 



The antero-superior surface (fades sternocostalis] (Fig. 416) is directed forward, 

 upward, and to the left. Its lower part is convex, formed chiefly by the right 

 ventricle, and is traversed near its left margin by the anterior interventricular 

 furrow. Its upper part is separated from the lower by the auriculoventricular 

 groove; it is formed by the auricles, and nreS pri*o ~ H* 

 occupied by the ascending ao,"uu , ^\uii&. 



jberculum Loweri. 

 usculi pectinati. 

 'sta terminalis. 



) returns the blood from the upper half of the 

 id back part of the auricle, the direction of its 

 rd. Its opening has no valves. 

 ), larger than the superior vena cava, returns 

 le body, and opens into the lowest part of the 

 'tion of its orifice being upward and inward, 

 Ive, the Eustachian valve. The blood which 

 rior vena cava is directed downward and for- 

 tricu-lar orifice, while that entering it through 

 upward and backward toward the auricular 

 on of the two currents in fetal life. 

 \us) opens into the auricle, between the inferior 

 ilar opening. It returns the blood from the 

 ;ted by an incomplete semicircular fold of the 

 xmmary valve, or valve of Thebesius. 

 venarum minimarum) are depressions in the 

 these are culs-de-sac, but about one third are 

 \nimae cordis), which return the blood directly 

 irt. 



o the lower fore part of the right auricle, 

 ng, or the tricuspid orifice (ostium venosum 



FIG. 416. Showing relations of opened heart to front of thorax. 



The postero-inferior surface (fades diaphragmatica) (Fig. 416), which looks 

 downward and slightly backward, is formed by the ventricles, and rests upon 

 the central tendon and a small part of the left muscular portion of the 

 Diaphragm. It is separated from the base by the posterior part of the auriculo- 

 ventricular furrow, and is traversed obliquely by the posterior interventricular 

 groove. 



The right margin of the heart is long, and is formed by the right auricle above 

 and the right ventricle below. The auricular portion is almost vertical, and is 

 situated behind the third, fourth, and fifth right costal cartilages about 3 cm. 

 from the middle line or half an inch from the margin of the sternum. The ven- 

 tricular portion, thin and sharp, is named the margo acutus; it is nearly horizontal, 



