The aphemetric compass : an instrument for measuring the degree of discriminative power, as regards contactile impressions, enjoyed by the skin and mucous membranes in certain affections of the nervous system / by John W. Ogle, M.D.

  • Ogle, John W. (John William), 1824-1905.
Date:
[1859]
Catalogue details

Licence: Public Domain Mark

Credit: The aphemetric compass : an instrument for measuring the degree of discriminative power, as regards contactile impressions, enjoyed by the skin and mucous membranes in certain affections of the nervous system / by John W. Ogle, M.D. Source: Wellcome Collection.

Provider: This material has been provided by The University of Glasgow Library. The original may be consulted at The University of Glasgow Library.

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    him entitled Recherches sur un moyen de mesurer I'Anaes- tliesie et THyperaesth^sie/' wherein he relates the particulars of eteven clinical cases in which by means of a pair of ordinary mathematical two-legged compasses, a deficiency, or an exaltation of contactile discriminative power in the fore-arm and legs was carefully ascertained and measured. In one case, although the two points in contact with the skin were 10, 15 and 20 centi- metres apart, yet the sensation perceived was that of a single point only. In one case of paraplegia the two points applied simultaneously to the feet were distinctly appreciated when only separated to the extent of 5 millimetres (the limit of distinction being here from 20 to 25 millimetres). In this case sensibility to pain was also exaggerated. Again at page 280 of the 41st number (January 1858) of the British and Foreign Medico.- Chirurgical Review is the description of an ingenious instrument called the sesthesiometer, and contrived by Dr. Sieveking for measuring the nearest distance at which two points made to impinge upon the skin in certain cases of paralysis, give a two- fold impression. This is accompanied by one or two cases showing the utility of the instrument,* and by a drawing from which it appears that it is not very dissimilar to the instrument the Stangenzirkle used in his physiological researches on the tactile sensations by Weber in the first instance, as aUuded to above (page 323). Similar also in principle to this one of Dr. Sieveking's is another instrument for the same purpose used by Dr. Brown- Sequard, and described and figured \>y that physiologist at page 346 of the first volume of his Journal de Physiologie, 1858. Tins latter instrument differs from that of Dr. Sieveking in having a longer handle, so that, as Brown-Sequard thinks, greater facility for application and for the simultaneous contact of the two points, so absolutely necessary, with the cutaneous siu'face is permitted. It occurred to me that several advantages would arise if an instrument could be constructed combining the principle of the beam-compass with that of the so-called mathematical one; and accordingly I had one fabricated which has appeared to me to answer the desired purpose.f * At page 504 of No. 45 of the same journal Dr. Sieveking gives a striking additional case, exemplifying the use of the instrument; showing the difference in the power of the skin, between the discrimination of painful impressions and that of merely contactile ones. + It was made for me by the well known fii-m of Messre. Elliott and Co., instrument makers. Charing Cross, London, whose foreman Mr. Becker, after learn- ing the principle on which I desired the instniment to be constructed, supplied all the calculations, &c., involved in the delicate graduation of the dial-plate, &c.