March io, 1910] 



NATURE 



ingenuity has been shown in devising methods by 

 which the vibrations of those sounds, as distinct from 

 the movements of the heart itself and the pulse in 

 vessels, can be recorded. The older methods were 

 subjective, and were consequently deficient in scientific 

 accuracy. Thus, if even a skilled observer listened to 

 the heart sounds and endeavoured to register their 

 sequence by closing a key which acted on a recording 

 lever, and if he endeavoured thus to register the 

 moment of the occurrence of the first or second 

 sound, or both, there was the inertia of the apparatus 

 and the possibility of personal error, which made the 

 observations of little value. It was desirable to have 

 objective methods by which the vibrations could be 

 actually recorded, and when one listens with the 

 stethoscope to the strangely muffled sounds, one 

 realises that to record the vibrations of such sounds 

 IS a remarkable achievement. At all events, the 

 beginning and the end of the sounds can now be 

 recorded. 



Hiirthle was the first to succeed in registering the 

 vibrations of the heart sounds. This he accomplished 

 in 1S92. His method was dependent on the use of a 

 microphone. A delicate microphone was placed on 

 the prongs of a wooden tuning fork, and the latter 

 was attached to the end of a large wooden stethoscope, 

 resting on the chest wall, over the apex of the heart. 

 The vibrations thus communicated to the microphone 

 altered a current flowing through an electro- 

 magnet, below which 

 was placed a Marey's 

 tambour (having a 

 thin iron disc fixed to 



the india-rubber), ^vva#-. 



and this, in its turn, '! 



transmitted its move- 

 ment to a second 

 very sensitive tam- 

 bour, which recorded 

 on a rapidly moving 

 surface. In this way, 

 vibrations of the 

 heart tone were re- 

 corded, and informa- 

 tion was obtained as to the exact moment when the 

 tone began. 



Soon afterwards, Einthoven investigated the subject 

 by means of a microphone and capillar\- electrometer, 

 and succeeded in registering with great accuracy the 

 two tones. Then he employed his remarkably \ 

 sensitive string galvanometer, and by means of this 

 instrument, and with the aid of photography, the 

 beginning, duration, and ending of the first and 

 second sounds were recorded. Even in records from the , 

 impulse of the apex, which shows numerous vibra- I 

 tions, those associated with the heart sounds are 

 readily identified. There can be little doubt that the 

 string-galvanometer method is most to be depended 

 on. 



Holowinski developed a method by the construction 

 of a kind of optical telephone. In the centre of a 

 telephone disc, a plate of glass, like the cover-glass 

 used in histolog\-, was brought against a plano- 

 convex lens, and in this way, when sounds caused 

 the telephone plate to vibrate, the interference rings 

 of Newton were produced. These varied with the 

 heart tones, and, by a photographic method, when the 

 picture of the variations w-as obtained, along with a 

 superposed cardiogramme (registration of movements 

 of apex impulse), Holowinski gave an interpretation 

 showing the position of the tones. The picture so. 

 produced, although beautiful and interesting physi- 

 callv, is rather confusing. 

 ,' Marbe devised a ver\' delicate Marey's tambour, or 



NO. 2ic6, VOL. 83] 



rather capsule, by which the vibrations of the heart- 

 tones regulated the flow of a current of acetylene gas. 

 This passed to a burner. The flame moved up and 

 down with each vibration, and it was allowed to 

 impinge on a moving band of paper. On this, with 

 each vibration, a ring of soot was formed, and a 

 picture of the heart tones was imprinted on the paper. 

 The method is easy, and the results are easily 

 interpreted. 



Another method has been devised by Gerhartz. He 

 caused a membrane (which received the sound waves) 

 to carry, vertically to its surface, a delicate glass rod, 

 which, at the other end, bore a small metallic mirror, 

 placed between the poles of an electro-magnet. The 

 arrangement is somewhat complicated, and it did not 

 give striking results. 



The last method we shall notice is that of Prof. 

 Otto Weiss. It is entirely mechanical, and is 

 independent of microphones and electrical appliances, 

 being a clever modification of the phonoscope, by 

 which, some years ago, many were amused by 

 watching the play of colours produced in a soap film 

 by the sounds of speech. Weiss's method consists in 

 the employment of a soap film, in the centre of which 

 there is attached the end of a silvered thread. The 

 other end of the thread is fixed to a lever connected 

 with a carrier. Vibrations are carried by a special 

 funnel-shaped tube from the heart to the phonoscope. 

 This is enclosed in a box having in its walls lenses 



miimmmmmMmmmmmmtmmmmmmmmmmmHmmmmmmm^^ 



Human Heart Souqds. The upper cur\-e 

 The middle cui »e shows the heart 

 tracing. (Weiss.) 



is a cardiogramme of the apex beat. The lower is that of i/ioo sec 

 sounds. Read firom right to left. The first sound is the larger 



SO adjusted that a photograph can be taken of the 

 silvered thread and of its movements. The photo- 

 graph, of course, is taken on a moving sensitive plate. 

 The inertia of the system is remarkably small, the 

 weight of the soap film and of the lever being about 

 0000054 grm. All the parts are extremely light. The 

 apparatus is so sensitive that the vibrations of a 

 whisper can be recorded ; the swing is aperiodic ; and 

 its moment of arrest is o'oi see. It is said to follow 

 very frequent vibrations. An example of a tracing 

 thus obtained is given in the figure. 



In his interesting monograph. Prof. Weiss gives 

 examples of tracings of cardiac sounds along with 

 the carotid pulse, of foetal heart sounds, of the modifi- 

 cations of the sound caused by mitral insufficiency, 

 mitral stenosis, aortic stenosis and insufficiency, and 

 of anaemic sounds. All this shows the possibility of 

 employing the method for clinical purposes. Finally, 

 bv an ingenious arrangement. Prof. Weiss has been 

 able to reproduce the sounds by means of a telephone. 

 A flame from a suitable lamp falls on a selenium cell 

 in the circuit of which is a telephone. Interposed in 

 the path of the beam of light, a disc is rotated having 

 the cur\-es of the heart sounds cut out on its margin. 

 As it is rotated, the effect of the intermittent light on 

 the selenium cell is such as to reproduce the heart 

 tones in the telephone. Such an arrangement may be 

 useful in teaching. 



John G. McKendrick. 



