THE MECHANISM OF THE CIRCULATION. 



the moment when the intraventricular tension just rises above the 

 aortic. 1 



Although the impulse of the heart is not the principal cause of the 

 first sound, as was maintained by Magendie, yet it may be an auxiliary 

 and occasional cause. The first sound can be heard when the chest wall is 

 removed, and also when, by filling the pericardium with fluid, the heart 



is prevented from strik- 

 ing against the stetho- 

 scope. If, however, a 

 board be applied to the 

 exposed heart, the first 

 sound is increased in 

 loudness. In quietude 

 and the supine position 

 the impulse is probably 

 of no account, but under 

 the opposite circum- 

 stances the first sound 

 may very considerably 

 increase. According to 

 Chauveau and Faivre, 

 the vibrations causing 

 the sounds of the heart 

 can be felt by a finger 

 placed over the region 

 of the valves. Eecently 

 the sounds have been 

 successfully recorded by 

 means of the micro- 



FIG. 19. Diagram of Hiirthle's experiment. M, microphone; phone. Hurthle in- 

 E, battery ; In, induction coil ; S' , S", keys ; T, tele- serted the microphone 

 phone; g, frog gastrocnemius ; A', cardiograph; A", f i T , r imQ rv Hrpiiit 

 myograph ; T, T", tambours. 



of a du Bois Eeymond 



coil, and placed a frog muscle preparation in connection with the 

 secondary circuit. A lever attached to this muscle marked the moment 

 of excitation, when the sound of the heart reached the microphone, and 

 closed the primary circuit. 2 



By Einthoven and Geluk 3 a similar method was employed, but 

 they registered the effect produced by the sounds on the microphone 

 circuit by means of a capillary electrometer. The movements of the 

 electrometer are photographed on a moving sensitized plate. Holowinski 

 has photographed the sounds by means of the optical telephone invented 

 by Babinet and Fizeau. 4 



That the sounds are compounded of several tones, is shown by 

 the photographs of Einthoven and Geluk. Each sound gives rise to a 

 succession of vibrations of the mercury meniscus. The first sound 

 was found to show itself earlier when the microphone was applied 



1 R. Quain denies either the valvular or muscular origin of the first sound. He ascribes 

 the sound to the impact of the blood against the resistance in the aortic orifices (Lancet, 

 London, 1897, vol. i. p. 1672 ; Proc. Hoy. Soc. London, 1897, vol. Ixi. p. 331), but there 

 are many reasons for regarding this view as an impossible one. 



2 Arch.f. d. ges. PhysioL, Bonn, 1895, Bd. Ix. S. 263. 

 * Ibid., 1894, Bd. Ivii. S. 617. 



4 Holowinski, Arch, de physiol. norm, etpath., Paris, 1896, tome xxviii. p. 893. 



