. A Reference handbook of the medical sciences : embracing the entire range of scientific and practical medicine and allied science. ent. The chart is attached to the shelf (E),and can be pressed at will against the pencil-point whenpassing over a scotoma. The method of examination is as follows : The patientis seated before the instrument, with his chin in the restand his eye fixed on the central object. The eccentricobject is started from the periphery by the crank, and,following the wire, moves in ever-decreasing circlesuntil it reaches the centre. If the object is perceivedthroughout its e
. A Reference handbook of the medical sciences : embracing the entire range of scientific and practical medicine and allied science. ent. The chart is attached to the shelf (E),and can be pressed at will against the pencil-point whenpassing over a scotoma. The method of examination is as follows : The patientis seated before the instrument, with his chin in the restand his eye fixed on the central object. The eccentricobject is started from the periphery by the crank, and,following the wire, moves in ever-decreasing circlesuntil it reaches the centre. If the object is perceivedthroughout its entire course, any limitation of the field,central or eccentric, may be excluded. The object slidesin a groove on the traveller, so that it will meet the half-distance between any two wires. In this way any andevery point of the field can be tested. The meridian isindicated by the arm on the circle, graduated to 360°,which forms the outer edge of the perimeter. Both ob-jectives are held by a small bulb-pointed pin which isclasped by springs. They are made of card-board andcan be of any size or color desired. A card, 5 centime-. Fig. 4599.—Priestley Smiths Perimeter. tres square, with parallel lines fixed to the traveller maybe used to show the meridian in astigmatism. Thisperimeter gives the means of making a quantitative testof the sensitiveness of the retina. In many cases wherethe retina is non-sensitive to the common test of a smallwhite object, it may be excited by a bright light, such 662 REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. as the electric light. The brass spiral wire serves as oneconductor, and a strip on the arm as the other. The
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectmedicine, bookyear188
