DISEASES OP THE HEART. 93 



When there is a double murmur, both systolic a.nd diastolic ; these 

 also may arise from disease of the aortic orifice alone; the former 

 being a murmur caused by the flow of blood from the heart ; the 

 latter by its regurgitation. 



Again, when there is a sirtgle systolic murmur, it may be caused 

 by disease of the mitral valve, permitting the blood to regurgitate 

 into the left auricle from the ventricle, when the latter contracts. 



The spot where all endocardial murmurs are heard most distinctly, 

 is immediately over the valve which originates them. And the space 

 under which the cardiac valves lie, may be said to be comprised 

 beticeen the lower margin of the 'Srd left costal cartilage, and the 

 lower margin of the Uh; extending inwards to the middle of the 

 sternum. Here it is that almost all murmurs are heard most clearly. 



The method of distinguishing them from each other is based on 

 the fact that the murmur will be conveyed along the direction of the 

 column of fluid whose vibration causes it. 



Thus if a murmur be seated at the aortic valve, it will be heard 

 most clearly over the left half of the sternum, between the Srd and 

 Ath costal cartilages. But the sound will also be conveyed with 

 tolerable clearness in the course of the aorta and its branches ; that 

 is to say, upwards and between the second and third ribs of the right 

 side — perhaps it will also be heard in the carotids. 



If the disease (which is very rare) were seated in the 'pulmonic 

 valves, the murmur would follow the course o^ the pulmonary artery, 

 upwards between the 2nd and 3rd ribs of the left side. 



If it were seated in the mitral valve, the murmur would be lost if 

 the stethoscope were moved upwards ; but would still be heard dis- 

 tinctly if it were moved downwards towards the apex of the heart. 



If the murmur is heard plainly in both directions, then both aortic 

 and mitral valves are probably diseased. 



There are some few circumstances which must be taken into 

 account in estimating the value of endocardial murmurs as signs of 

 valvular disease. 



For first, they are sometimes absent altogether when the patient is 

 in repose ; although they may be excited by causing the patient to 

 move about, so that the heart may beat more forcibly. 



Secondly, the loudness of the sound is by no means a measure of 

 the extent of the disease ; for in long standing cases, where a 

 diseased orifice has become very contracted, the sound often becomes 

 very feeble indeed. 



Thirdly, very violent action of the heart alone, without valvular 

 disease, may occasion a murmur ; this often happens to children ; 

 seldom to adults. 



Fourthly, if the heart is embarrassed by deformity of the chest, 

 or if it is too much pressed upon by the stethoscope, murmurs may 

 be created. 



