On the differential stethoscope and its value in the diagnosis of diseases of the lungs and heart / by George L. Carrick.

  • Carrick, George L., 1840-1908.
Date:
[1873]
Catalogue details

Licence: Public Domain Mark

Credit: On the differential stethoscope and its value in the diagnosis of diseases of the lungs and heart / by George L. Carrick. Source: Wellcome Collection.

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    wooden cylinder, resembling a dumpy little uniaural stethoscope (a). One end of the cylinder expands into a cup (b), which is applied to the chest for collecting sound, while to its other extremity are attached two tubes (c, c). These tubes communicate with the hollow cylinder, are about 10 inches in length, and con¬ sist of 3 inches of flexible (d), and about 7 inches of metallic tubing (e). The former is joined to the wooden cylinder, while to the free ends of the latter the small ivory knobs (f) are attached. The two metallic tubes are connected by a jointed bar (G). lhe joint allows of the partial separation and approach of the tubes necessary for adjustment in respect of the ears. A band of elastic material (h) connects the two tubes at a point between the bar and the ear extremities.” The auscultator can thus, while keeping Ins head fixed, move the instrument right or left, upwards or down¬ wards. The mechanism of Dr Cammann’s stethoscope served as the model upon which Dr Scott Alison’s differential stethoscope was made, although the two instruments are constructed upon entirely different acoustic principles. Before passing on to a description of the differential stethoscope, it may be well to state in what respects Cammann’s differs from the ordinary stethoscope; and this is all the more necessary, as we shall presently have to institute comparisons between Alison’s and Cammann s instiument. Dr Cammann’s binaural stethoscope possesses many advantages over the ordinary one. Firstly, By allowing both ears to listen to the same sound at the same time, the acoustic impression is cleatei, louder, and fuller. The rule, that a more vivid effect is produced by the use of two organs than by the use of one, is as applicable to acoustics as to optics. Secondly, Many fine sounds which cannot be well made out by the ordinary stethoscope are clearly heard, by the binaural one. To such belong the fine arrowroot, buzzing, moaning, and indeterminate sounds so often heard in the first stage of phthisis. Crepitation also, whether moist or dry, is better heaid with Cammann’s instrument. Thirdly, The chest ^can be moie quickly and conveniently examined with Cammann s stethoscope, because of the instrument’s flexibility. It is worthy of note, however, that all binaural stethoscopes, from Leared’s to Cammann’s, are constructed upon the same principle as the ordinary uniaural instrument. They differ from the latter in two points only ; firstly, in conducting sound to both ears instead of to one ear; and, secondly, in air being the conductor instead of the material (whether wood, gutta-percha, ivory, or metal) of which the stethoscope is constructed.1 They all consist of a single collector 1 Of the distance to which sound can travel through a tube containing air, an interesting case is cited by Professor Tyndall, from “the celebrated French philosopher Biot, who observed the transmission of sound through the empty water-pipes of Paris, and found that he could hold a conversation in a low voice through an iron tube 3120 feet in length.”—Sound, by John Tyndall, - F.R.S., p. 13.