THE HEART. 



205 



Area of Cardiac Dulness. The area of cardiac dulness corresponds to the 

 area uncovered by lung and in contact with the chest-wall. This is the area of abso- 

 lute dulness. It begins opposite the fourth costal cartilage and extends down the 

 sternum, between the median line and left edge, to the liver dulness below opposite 

 the sixth costal cartilage. Toward the left side it arches from the fourth left costo- 

 sternal junction to the apex beat. The area of so-called relative dulness caused by 

 overlapping of the lungs extends along the right edge of the sternum to opposite the 

 upper border of the third rib above, and to the left follows parallel to the left border of 

 the heart to the tip of its apex. Below it blends with the liver dulness (Fig. 221). 



The area of cardiac dulness may be increased not only by the enlargement of the 

 heart itself but by pericardial effusions and disease such as aneurism of the great vessels. 



In an early stage of pericardial effusion and also in aneurism there may be an 



FIG. 220. Relations of the heart, its valves, and the great blood-vessels to the surface of the chest. 



extension of the area of dulness upward. In a later stage of pericarditis the lateral 

 area of dulness becomes increased. 



Cardiohepatic Angle (Ebstein). This is the angle formed by the right 

 border of the heart as it meets the liver. It is a more or less resonant area in the 

 fifth right intercostal space. Below it is the liver dulness and above and towards 

 the median line is the heart. 



VALVES OF THE HEART. 



There are two types of valves in the heart: the bicuspid {mitral'} and tricuspid 

 between the atria (auricles) and ventricles, and the two sets of semilunar valves at 

 the entrance of the pulmonary artery and aorta. (See Fig. 220.) 



The bicuspid valve is the most important and is the deepest seated. It lies 

 at the edge of the left border of the sternum opposite the fourth costal cartilage. 

 It separates the left atrium and ventricle and lies nearly transversely. 



