354 



THE HEART. 



internal mammary arteries, and by twigs of the inferior phrenic arteries. The veins run to 

 the azygos, internal mammary and phrenic trunks. Its lymphatics pass to the mediastinal 

 glands. Nervous filaments are furnished to it by the phrenics, vagi and sympathetic. The 

 visceral pericardium is supplied by the vessels and nerves of the heart. 



THE HEART. 



The heart is a hollow muscular organ, divided by a longitudinal septum into a 

 right and a left half, each of which is again subdivided by a transverse constriction 

 into two compartments, communicating with each other, and named auricle and 

 ventricle. Its general form is that of a blunt cone. Enclosed in the pericardium, 



it is placed behind the sternum and the costal car- 

 i , ,- tilages (fig. 318, p. 366), the broader end or base 



-I i if/ being directed upwards, backwards, and to the right, 



and placed opposite the sixth, seventh and eighth 



Fig. 306. THE HEART AND GREAT VESSELS FROM BEFORE. (R. Quain.) 



The pulmonary artery has been cut short close to its origin in order to show the first part of the 

 aorta. 1, right ventricle ; 2, left ventricle ; 3, root of pulmonary artery ; 4, 4', arch of aorta ; 4", 

 descending aorta ; 5, appendix and anterior part of right auricle ; 6, those of left auricle ; 7, 7', inno- 

 minate veins joining to form the superior vena cava ; 8, inferior vena cava below the diaphragm ; 9, one 

 of the hepatic veins ; + , right, + + , left coronary artery. 



Fig. 307. THE HEART AND GREAT VESSELS FROM BEHIND. (R. Quain.) | 



1, right ventricle; 2, left ventricle ; 3, right pulmonary artery ; 3', its branches in the root of the 

 right lung ; 3", the same of the left ; 4', arch of aorta ; 4", descending aorta ; 5, right auricle ; 6, is 

 placed on the division between the right and left auricles ; 7, superior vena cava ; 7', left innominate 

 vein ; 8, inferior vena cava ; 9, right hepatic vein ; 10, 11, 12, right pulmonary veins ; 13, 14, left 

 pulmonary veins ; + , + , branches of the right and left coronary arteries. 



dorsal vertebrae ; while the apex points downwards, forwards, and to the left. In the 

 living subject its stroke against the wall of the chest is felt in the space between 

 the cartilages of the fifth and sixth ribs, a little below and to the inner side of the 

 left nipple (3j inches from the middle line of the sternum and 1 J inch below the 

 nipple) : in the dead body the apex is a little higher than during life. The heart, 



