The ophthalmoscope : its varieties and its use / translated from the German of Dr. Adolf Zander by Robert Brudenell Carter ... with notes and additions by the translator.

Adolf Zander

Date:: 1864

Credit: The ophthalmoscope : its varieties and its use / translated from the German of Dr. Adolf Zander by Robert Brudenell Carter ... with notes and additions by the translator. Source: Wellcome Collection.

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

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$THE OPHTHALMOSCOPE. oo'cQ^Oo ■ INTEODUCTION. EVERY great discovery, that marks an epoch in the history of science, must be in preparation for a variable length of time, and in diflferent ways, prior to the advent of the genius who calls it into being; and who may have, as one of his chief functions, to estimate at their true value, and to unite into a coherent whole, scattered materials of much importance, but previously wasted because misunderstood. Thus also it befel with regard to the invention of the Ophthalmoscope. This instrument, after being foreshadowed in a twofold manner, at length received from Professor Heinrich Helmholtz a realization that has rendered it the greatest discovery of modern times in the domain of Ophthalmology; a discovery the fruits of which we are not yet in a position to estimate completely. Its origin may be traced to successive endeavours to solve two problems : the first being, why the eyes of men and animals some- times shine with a reddish lustre; and the second, why the interior of an eye more usually appears dark. From the most ancient times a glittering of the eyes had been observed in animals possessing a tapetum, especially in dogs and cats. It was ascribed to a spontaneous development of light from the eye, under the influence of the nervous system, and was supposed to become more vivid when the animal was excited; an opinion that had its adherents even until very recently. The first to controvert it were Prevost, Rudolphi, and Gruithuisen (1810), the first of whom discovered that no glitter could be seen in a completely darkened room, and that the appearance was therefore to be considered only as a reflection of incident rays. The last traced the effect to the operation of the tapetum, combined with a great refraction by the crystalline lens; and Rudolphi first observed that, in order to see the glitter, the spectator must look into the eye in a certain determinate direction. B$