THE HEART. 



243 



the serous layer of the pericardium is here reflected from the one to the 

 other. In the remainder of its extent the organ is entirely free within 

 the sac of the pericardium. The convex anterior surftice looks somewhat 

 upwards as well as forwards towards the sternum and costal cartilages : 

 from these it is partly separated by the plenne. The lungs "also 

 advance over it to some extent, and encroach still farther dining 



Fig. 165. — View of the Heart, and Fig. 105. 



Great Vessels FROM before (R. Quaiu). 

 One-tuird the Natural Size. 



The piihnonaTy 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 the pulmonary 

 artery ; 4, 4', arch of the aorta ; 4", the 

 descending thoracic aorta ; 5, the ajipen- 

 dix and anterior part of the right auricle ; 

 6, those of the left anricle ; 7, 7', inno- 

 minate veins joining to form the vena cava 

 superior ; 8, inferior vena cava below the 

 diaphragm ; 9, one of the large hepatic 

 veins ; + , placed in the right auriculo- 

 ventricular groove, jjoints to the right or 

 posterior coronary artery ; + , + , placed 

 in the anterior interventricular groove, 

 indicate the left or anterior coronary 

 artery. 



inspiration, so as in that condi- 

 tion to leave only a triangular 

 part, not more than two square 

 inches in extent, uncovered.* The 

 posterior or under surface is 

 flattened, and rests on the dia- 

 phragm. Of the two borders or 

 margins formed by the meeting 

 of the anterior and posterior sur- 

 faces, the right or lower border, 

 called margo acvtus, is compara- 

 tively thin, and is longer than the upper or left border, which is 

 more rounded and is named margo ohtirsus. 



A deep transverse groove, the auricido-vcniricular furrow, inter- 

 rupted in front by the root of the pulmonary artery, divides the 

 heart into the auricular and the ventricular portions ; and on the ven- 

 tricular portion two longitudinal furroivs, situated one on the anterior, 

 the other on the posterior surface, mark its division into a right 

 and left chamber. They extend from the base of the ventricular 

 portion, and are continuous one with the other a little to the right 

 of the apex, which thus appears to be formed entirely by the wall of the 

 left ventricle. The anterior longitudinal furrow (fig. 165 -t- + ) is nearer 

 to the left border, whilst the posterior furrow approaches nearer to the 

 right border of the heart, the right ventricle forming more of the 

 anterior, and the left more of the posterior surface of the organ. 

 In the transverse and longitudinal furrows run the coronary or cardiac 



* This uncovered part may be marked off on the surface of the chest by two lines 

 drawn from the apex-point to the middle line of the sternum, one horizontal, the other 

 extending obliquely upwards to between the fourth cartilages. 



K 2 



