324 



NATURE 



[May 12, 1910 



increased in strength to the extent of something like twenty 

 times. If still greater magnifications are required than can 

 be obtained with one relay, the simplest method would 



Fig. 6. — Telephone Relay in brass case with upper arm raised i^x cleaning th» contents 



seem to be to employ two' relays working in tandem. 



Therr combined power would then be 400 times. In the 



majority of cases it is 



not necessary to add to 



the natural electrical 



damping of the reed, 



but if a piece of soft 



rubber be made to touch 



it, the voice can be 



transmitted with greater 



clearness even than if 



the conversation were 



tiaking place ordinarily 



in a room. This may 



be due to the complete 



absence of echoes. 



By means of the local 

 regulating winding (see 

 Fig. 2) the metal con- 

 tact M, O is transformed 

 into the most exquisitely 

 delicate microphone, 

 more sensitive, there is 

 ever}' reason to believe, 

 than could be formed by 

 light pressure between 

 carbons. Such a micro- 

 phone has rendered 

 possible the construction 

 of an electric stetho- 

 scope, an instrument by 

 the use of which the 

 sound of the heart or 

 other internal organs 



may be greatly magnified. This, I have been informed, 

 may render it possible to detect in the earlier stages heart 

 disease, aneurism, and gall-stones. 



NO. 2 IIS, VOL. 83] 



Fig, 4 is a diagrammatic illustration of the stethoscope: 

 .\ is the front part, and consists of a shallow brass cell 

 faced by a thin ebonite diaphragm. A is placed upon the 

 part of the body to be examined, say the hear' • 

 the beating of the heart is communicated 

 the ebonite diaphragm, then to the air insii 

 the tube B, and thus the metal diaphragm I> 

 is set in vibration. M, O, as before, are tlie 

 osmium-iridium contact-pieces. M is mounti-d 

 on the diaphragm, and O on the steel reed P. 

 The magnet N, S and the reed are carried ' "■ 

 a brass frame E, which is pivoted or hin^ 

 at the lower support Y. The conduction spa 

 is formed between the contacts M, O by turn- 

 ing the fine adjusting screw W, and by the 

 automatic action of the local current from, the 

 cell C flowing through the winding K and 

 round the magnet. T is a special telephone 

 trahsformer of equal windings of, say, 20 ohms 

 resistance in the primary and in the secondary. 

 The electric stethoscope in its present form 

 causes the sound of the heart to be three times 

 as loud as in the ordinary stethoscope. This 

 is scarcely sufficient for practical purposes ; liut 

 if a telephone relay, such as I have previously 

 described, be attached to the wires x of the 

 transformer, the two instruments combined 

 raise the intensity of the sound some twenty 

 times and more, and this is ample for all 

 ordinary purposes. The sound to be' examined 

 is picked up by the end of the tube A, and is 

 heard in the telephones of a head-piece attached 

 to the relay. 



At the invitation of two physicians I took 

 the complete instrument, stethoscope and relay, 

 to the London Hospital, where it was tested 

 upon a number of diseased heart cases. N0I 

 being a doctor myself, I cannot discuss the 

 merits of the instrument with regard to its 

 medical value, except to say that it seemed tc 

 render diagnosis particularly easy and revealec 

 some phenomena only' previously suspected 

 From a. sound-magnifying point of view , thi 

 general, results were as follows. When th( 

 instrument was applied directly to the heart thi 

 sound of the beats given out in the telephonei 

 was uncomfortably loud, and easily heard by thi 

 patient . and all those that stood round, and this even i 



the telephones were in position on the head of the opera* 

 The stethoscope as used increased the heart-beats to tlF 

 almost complete exclusion of the shriller or breathiij 



