MITEAL STENOSIS. 255 



murmur is accepted, every valve orifice, except the aortic, may 

 be the site of a murmur. 



The presystolic murmur of mitral stenosis is audible over a 

 curiously limited area internal to the cardiac impulse. Both 

 thrill and murmur are communicated from the solid structures 

 of the heart to the chest wall, and by firm pressure with the 

 stethoscope the murmur can be modified or even suppressed. 



A systolic tricuspid murmur is common in the later stages of 

 the disease. This murmur is heard over an area corresponding 

 to the tricuspid valve. The tricuspid orifice is comparatively 

 superficial, and lies obliquely across the vertical mid-line of the 

 sternum opposite the fourth and fifth costal cartilages and 

 the fourth intercostal spaces. The murmur is diffused over a 

 considerable area of the lower part of the sternum, and often 

 extends as far outwards as the cardiac impulse, which it is well 

 to bear in mind is often caused by the right instead of by the left 

 ventricle in these cases. The structure of the tricuspid fibrous 

 ring is similar to that of the mitral, and the valve yields even 

 more readily to pressure. Indeed the tricuspid valve may be 

 said to be normally incompetent under increased pressure, this 

 being a device to obviate over distension and even rupture of 

 the right ventricle under circumstances of sudden muscular 

 effort. 



The increased pressure in the pulmonary circuit may result in 

 atheromatous changes in the pulmonary artery and temporary 

 incompetence of the pulmonary valves. In such cases a diastolic 

 murmur appears a short distance to the left of the sternum 

 just outside the position of the aortic valves. The murmur is 

 transitory, disappearing when the circulation improves, and there 

 appears good reason for the belief that it is really produced at 

 the pulmonary orifice which is displaced in the same direction as 

 the conus arteriosus, to the position of "which reference will later 

 be made. 



The disappearance of the second sound at the impulse of the 

 heart, which is a common occurrence in mitral stenosis, is 

 probably due to interposition of the right ventricle in front of 



