vii MECHANICS OF THE HEART 197 



venous auriculo-ventricular valves, the second on the vibration of 

 the arterial or sernihmar. The) 7 also succeeded in producing an 

 artificial sound in an excised aorta, by throwing the valves into 

 sudden tension. 



Williams and the Dublin Committee of the British Association 

 (1835) undertook to test this theory, and confirmed by ingenious 

 experiments the part which referred to the second sound. They 

 noted that the second sound was abolished when the play of the 

 semilunar valves was impeded, as when the apex was cut, and the 

 blood prevented from issuing by the arteries. They, however, 

 found the valvular theory to be incorrect as regards the first 

 sound, observing that it persisted even when the heart was void of 

 blood and excised from the animal. Accordingly they postulated 

 a purely muscular origin for the first sound a theory that was 

 taken up later on by Ludwig and Dogiel (1868), -and confirmed by 

 numerous experiments. 



Wollaston had already shown in 1810 that the contraction of 

 a muscle can produce a bruit. Ludwig further showed that 

 the muscles of the ventricle, which are interwoven in various 

 intricate ways, and form two cavities with trabeculated inner 

 surface, must be better able than skeletal muscles to generate a 

 bruit when suddenly thrown into tension. 



The demonstration of the muscular theory does not, however, 

 exclude there being some truth in the valvular theory of the first 

 sound. Wintrich (1875), by means of Helmholtz' resonators, 

 succeeded in analysing the first sound, and recognised it to be the 

 result of two components : a deep sound (or rumble) of a muscular 

 character, and one or more sharp tones, depending not merely 

 upon the vibrations of the auriculo-ventricular, but also upon 

 those of the semilunar valves, demonstrated, as above, by 

 Ceradini. 



Even with these additions, however, the theory of the sounds 

 of the heart was incomplete. Talma (1880) examined the valvular 

 theory from the standpoint of the laws of acoustic vibrations, and 

 objected that since the valves are immersed in a fluid of lower 

 specific gravity than themselves, the sounds that are generated when 

 they are thrown into sudden tension must essentially depend upon 

 the vibrations of the blood, rather than on those of the valves. 



Webster (1882), however, showed that Talma had overlooked 

 one fact, namely, that both the first and second sounds can be 

 resolved into several components, by the help of a resonator. He 

 attempted to prove that the effects of the vibrations of the semi- 

 lunars and also of the walls of the bulbi arteriosi, can be dis- 

 tinguished from the effects of the vibrations of the blood in the 

 second sound. To this we would add that the valvular vibrations 

 that contribute to the formation of the second sound, coincide, not 

 with the closiny of the valves, as is stated in every text-book, but 



