208 CIRCULATION. 



These facts, to which, we may add the modifications of 

 the first sound in disease, so as to leave only the valvular ele- 

 ment, taken in connection with the fact that the first sound 

 occurs when the ventricles contract, and necessarily accom- 

 panies the closure of the auriculo-ventricular valves, show 

 pretty conclusively that these valves produce at least a cer- 

 tain element of the sound. In further support of this opinion, 

 we have the fact that the first sound is heard with its maxi- 

 mum of intensity over the site of the valves, and is propa- 

 gated downwards along the ventricles, to which the valves 

 are attached. 



Actual experiments are not wanting to confirm the above 

 view. Chauveau and Faivre 1 have succeeded in abolishing 

 the first sound by the introduction of a wire ring through a 

 little opening in the auricle into the auriculo-ventricular ori- 

 fice, so arranged as to prevent the closure of the valves. 

 When this is done, the first sound is lost ; but on taking it out 

 of the opening, the sound returns. These observers also 

 abolished the first sound by introducing a small curved 

 tenotomy-knife through the auriculo-ventricular orifice, and 

 dividing the chordae tendinese. In this experiment a loud rush- 

 ing murmur took the place of the sound. We have already 

 alluded to the experiment of introducing the finger through 

 an opening in the auricle ; if this be done, and the heart be 

 auscultated at the same time, the valves will be felt striking 

 against the finger in unison with the first sound. 



The above observations and experiments settle beyond 

 question the fact that the closure of the auriculo-ventricular 

 valves produces one element of the first sound. 



The other elements which enter into the composition of 

 the first sound are not as prominent as the one we have just 

 considered, though they serve to give it its prolonged and 

 " booming " character. These elements are, a sound like that 

 produced by any large muscle during its contraction, called 



1 Op. cit., pp. 30 and 31. 



