290 THE MECHANICS OF THE HEART 



The cardiac sounds have been recognized &t an early date. Harvey, 

 for example, states that the delivery of a quantity of blood into the 

 arteries produces a pulse which can be heard within the chest, but 

 Laennec^ was the first to describe the character of the sounds and to 

 make use of them for clinical purposes. Graphic records of them have 

 been obtained by Donders (185G), Martin (1888) and Hurthle (1892), 

 but the first really satisfactory method of registration has been devised 

 by Einthoven and Geluk.^ The sounds transmitted by a stethoscope 

 were caught upon a microphone. The currents were then led off to a 

 capillary electrometer, and photographed by projecting the move- 

 ments of the mercurial column of this instrument upon sensitive paper 

 moved with a certain velocity. In recent years, this means of regis- 

 tration has been displaced by the string galvanometer. Frank^. 

 has devised an instrument without a microphone, the sounds being 

 transferred directly from a stethoscope onto a membrane carrying a 

 reflecting mirror. It should be mentioned, however, that the records 

 so obtained are not always satisfactory, because they really represent 

 a combination of phonogram and cardiogram. Under ordinary con- 

 ditions, however, it is not difficult to differentiate between the rapid 

 oscillations caused by the cardiac sounds, and the slow deflections 

 produced by the contraction of the cardiac musculature. By means 

 of the method described previously, Einthoven* has succeeded in 

 registering a third heart sound which, however, cannot usually be 

 heard with the stethoscope. 



The first sound occurs during ventricular systole. It begins with 

 the "setting" of the ventricles and continues until the highest intra- 

 ventricular pressure has been produced. This point coincides with 

 the beginning of the plateau, when the semilunar valves are forced 

 open. It is loud at first, but becomes less intense toward the end 

 of the ventricular contraction. It lasts 0.07 to 0.10 sec. 



It may be concluded that the first sound of the heart is due very 

 largely to the friction noises emitted by the contracting ventricular 

 musculature,^ because: 



(a) It is also produced by the exposed and bloodless heart, and also by excised 

 portions of the ventricle and by apex preparations. 



(6) The sound begins before the closure of the auriculoventricular valves 

 and continues practically throughout ventricular systole until the muscle fibers 

 have attained their maximal degree of shortening. 



in the tissue situated between the heart and the chest wall, as well as by structural 

 alterations in the musculature of the organ itself (hypertrophy and dilatation). 

 Moreover, when one or several of the valves become incompetent, the resulting 

 murmurs seriously impair the normal character of these sounds. 



1 De r auscultation, Paris, 1819. 



2 Pfluger's Archiv, Ivii, 1894, 617. 



^Kongr. fur inn. Med., Wiesbaden, xxv, 1908; also see: Weiss, Das Phono- 

 scope, Med. nat. Arch., Berlin and Wien, i, 1908. 

 * Pfluger's Archiv, cxx, 1907, 31. 

 6 Q, j_ B. Williams, Rep. Brit. Assoc, for the Adv. of Science, London, 1836. 



