EXTERIOR OF THE HEART 



509 



The long axis of the heart is therefore slightly more horizontal than vertical, and slightly 

 more antero-posterior than transverse. The atria are posterior to rather than above the ven- 

 tricles. To arrive approximately at the longitudinal axis, it is necessary to select the central 

 point of the base. By cutting the vessels short in several hearts, hardened by formalin before 

 removal, a point immediately to the left of the left lower pulmonary vein was selected in deter- 

 mining the data above given. A steel pin was passed through this point to the apex cordis, and 

 the angles controlled by frontal and transverse sections of the thorax. Mention of angular 

 measurements of the axis of the heart could be found only in the tex-t-books of Testut and 

 Luschka; the former gives 40° to the horizontal plane, the latter 60° to the mid-sagittal. 

 Luschka's angle appear to be too large; but further investigation in this direction is desirable. 



Fig. 423. — Sterno-costal Surface of the Heart. 



Right common 

 carotid artery 



Right innominate 



Right int. mam- 

 mary vein 



Ascending aorta 

 Vena cava superior 



Coronary sulcus — -- 



Right ventricle 



/ 



Left subclavian artery 

 Left inferior thyreoid vein 



Left innominate vein 



Left superior intercostal vein 

 Vestige of left common cardinal 

 Left pulmonary artery 



Left auricle 



^-— — Conus arteriosus 



. Margo obtusus 



Left ventricle 



Anterior longitu- 

 dinal sulcus 



Margo acutus 



Incisura apicis tordi 



Size and weight. — In the adult the heart measures about 12.5 cm. (5 in.) from base to apex, 

 8.7 cm. m in.) across where it is broadest, and 6.2 cm. (2 J in.) at its thickest portion. In the 

 male its weight averages about 312 gm. (eleven ounces), and in the female about 255 gm. 

 (nine ounces) . It increases both in size and weight up to advanced life, the increase being most 

 marked up to the age of twenty-nine years. The proportion of heart-weight to body-weight 

 is about 1:205 in the adult. 



EXTERIOR OF THE HEART 



In hearts which have been hardened by injection before removal from the 

 body, the regularity of the heart-cone is disturbed by a well-marked triangular 

 facet, imparted b}-- contact with the diaphragm. This facet is the diaphragmatic 

 surface [facies diaphragmatica], which is directed downward and shghtly back- 

 ward (fig. 424). It ends abruptly along a sharp margin extending from the apex 



