THE VALVULAK OEIFICES. 251 



requires heavy percussion, and cannot be determined with 

 anything like the same accuracy owing to the intervention of 

 resonant pulmonary tissue and the vibrant qualities of the 

 sternum. 



The valvular orifices of the cavities of the heart lie so closely 

 together that it is unsafe to assign a murmur to a definite orifice 

 because it happens to be loudly heard at a surface area corre- 

 sponding to the orifice in question. The valves which guard the 

 orifices of the right side of the heart lie more or less in front of 

 those belonging to the left cavities. This is especially the case 

 with the valves of the pulmonary artery and the aorta. In 

 diseased conditions the relations may become altered. The 

 aorta may displace the pulmonary artery considerably to the 

 left, and the tricuspid orifice may come more and more in front 

 of the mitral. Nevertheless, as a general rule, pulmonary, aortic 

 and tricuspid murmurs are best heard at spots corresponding to 

 the positions of the respective valves as projected on the surface 

 of the chest. The mitral valve is an exception, the murmurs 

 belonging to this valve are best heard where the left ventricle 

 impinges on the surface of the chest i.e., at or near the cardiac 

 impulse. 



The fibrous cusps of the valves are devoid of vessels. The 

 vegetations of early endocarditis are not actually on the free 

 edges of the valves, but lie in positions corresponding to the 

 points of maximum contact of the cusps involved. As the result 

 of inflammation the thinnest portions of the valves become con- 

 tracted, and then the vegetations may appear to lie on the free 

 edges. They appear on the side of the valve which is remote 

 from the blood pressure i.e., on the ventricular aspects of the 

 aortic and pulmonary valves, and on the auricular aspects of the 

 mitral and tricuspid segments. 



Aortic Disease. The aortic valve lies under cover of the left 

 edge of the sternum close to the lower border of the third left 

 costal cartilage. It is in this position the aortic diastolic 

 murmurs are earliest detected and best heard. The "aortic 

 cartilage " is the second right costal cartilage, and corresponds 



