340 Sir R. Quain. On the Mechanism by which 



explanation was first suggested to my mind many years ago by the 

 occurrence of a case of disease in which the aortic valves, being 

 completely broken down by disease, became inadequate to their 

 function. A murmur of such intensity was produced that it was 

 audible at 2 or 3 inches from the wall of the chest without any 

 intermediate communicating body. With a view to determine how 

 far this murmur might be conducted along the course of the cir- 

 culation, I examined the femoral artery. There I found that 

 the murmur was not conveyed to the ear, but a sound precisely 

 resembling the first sound was heard, a sound caused by the pressure 

 of the stethoscope resisting the motion of the blood in the artery, 

 which, the valves being destroyed, thus received the full force of the 

 ventricular contraction. My attention was thereby directed to the 

 obstruction offered by the aortic valves in health to the blood in 

 leaving the ventricle. I felt the case to be so interesting that I sub- 

 mitted it to a meeting of the Harveian Society ; and my observation 

 is recorded in the Minutes of the meeting April, 1852. 



From that time to the present I have taken every opportunity of 

 investigating the subject. Observations have been made on the 

 course of the circulation in the femoral artery under like circum- 

 stances by Durozioz, Moulie, von Bamberger, and others. These 

 observations, however, have had reference more especially to the 

 diagnosis of disease of the aortic valves, and I mention them here 

 only as indicative of interesting investigations having been made on 

 the femoral artery in cases of diseased aortic valves. The observers 

 named make no special reference to the first sound of the heart in 

 health. 



Objections may be offered to the explanation of the first sound of 

 the heart here brought forward, founded on the fact that this sound 

 is heard more distinctly at the apex of the organ, a point removed 

 from the seat of the valves. The observation is perfectly correct, but 

 the explanation is simple. The muscular walls of the heart are con- 

 nected, as above described, with the fibroid ring which is intimately 

 associated with the semi-lunar valves. The sound produced at these 

 valves is communicated to the apex of the heart through the fibroid 

 ring and the muscular walls, which at the moment of systole are 

 tense and firm. The sound thus conducted reaches that portion of 

 the heart which is uncovered, and which is in contact with the walls 

 of the chest. But, on the other hand, when opportunity offers it has 

 been found that the sound in question is heard over the aortic valves 

 more distinctly than in any other situation. A remarkable case of 

 this kind has been related by M. Cruveilhier, who was invited to see an 

 infant just born presenting a complete case of ectopia of the heart. 

 He says, " On examining the heart thus exposed, both sounds were 



