740 THE VASCULAR SYSTEM. 4 
is reflected, the lines of reflection corresponding with the orifices of the great 
vessels.! 
The apex (apex cordis), bluntly rounded, is formed entirely by the left ventricle. 
It is directed downwards, forwards, and to the left, and is situated, under cover 
of the anterior border of the left lung and pleura, behind the fifth left intercostal 
space, three and a-quarter inches from the anterior mesial line. 
The inferior surface (facies iaphragmatica) is formed by the ventricular part 
of the heart. It rests upon the diaphragm, chiefly on the central tendon, but, upon 
the left side, on a small portion of the muscular substance also, and it is divided 
into two areas—a smaller to the right side and a larger to the left side—by an 
oblique antero-posterior groove, the inferior interventricular sulcus. It is separated 
from the base by the posterior or inferior portion of the auriculo-ventricular sulcus. 
The antero - superior surface (facies sterno -costalis) is directed upwards, for- 
Aorta 
Left auricle 
Pulmonary artery 
Superior vena 
cava —— 
Left auricular appendix 
Right coronary 
artery 
Transverse branch of left 
Right auricular coronary artery 
appendix 
Interventricular branch of left 
coronary artery 
Right coronary 
artery 
Left ventricle 
Left marginal 
artery 
Right marginal — 
artery 
Right ventricle 
Fic. 546.—THE ANTERO-SUPERIOR SURFACE OF THE HEART. 
wards, and to the left. It lies behind the body of the sternum and the inner 
extremities of the cartilages of the third, fourth, fifth, and sixth ribs on the right 
side, and a greater extent of the corresponding cartilages on the left side. 
This surface is separated into upper and lower sections by the anterior portion 
of the auriculo- ventricular groove, which runs obliquely from above down- 
wards, and from left to right, from the level of the third left to that of the sixth 
right costal cartilage. The upper section of the surface, which is concave, is formed 
by the auricles; it is separated from the sternum by the roots of the aorta and the 
pulmonary artery, and is continuous laterally with the auricular appendices which, 
projecting forwards, embrace these great vessels. The lower section of the antero- 
superior surface is convex ; it is formed by the ventricular part of the heart, and is 
divided by an anterior interventricular sulcus into a smaller left and a larger right 
1 In the foetus and young child the auricular portion of the heart forms not only the base, but also the 
posterior part of the inferior or diaphragmatic surface. 
