On the photochemistry of the retina and on visual purple / translated from the German of Dr. W. Kühne ... Ed., with notes, by Michael Foster.

  • Kühne, W. (Willy), 1837-1900.
Date:
1878
Catalogue details

Licence: Public Domain Mark

Credit: On the photochemistry of the retina and on visual purple / translated from the German of Dr. W. Kühne ... Ed., with notes, by Michael Foster. Source: Wellcome Collection.

Provider: This material has been provided by the Augustus C. Long Health Sciences Library at Columbia University and Columbia University Libraries/Information Services, through the Medical Heritage Library. The original may be consulted at the the Augustus C. Long Health Sciences Library at Columbia University and Columbia University.

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    the isolated retina becoming fluoi-escent (see note B, p. 97) as it bleaches, loses its fluorescence as it becomes once more pui'ple : that is to say, the return of the visual pui'jile is accompanied by the dis- ajipearance of the visual white ; (2) that the retina bleached in siho during life is found when removed to be incapable of auto-regene- ration, and is at the same time devoid of fluorescence,—that is to say, when the i-etina is bleached in sita the visual white appears to be removed from the rods as it is formed. It is no great stretch to suppose that it is taken up by the retinal epithelium, and there, in the epithelium cells, reconverted into visual purple. And this further view is again supported by the facts that a solution of the retinal epithelium in bile-salt solution, free from ether, is rose-coloured in the dark, becomes colourless when exposed to light, and rose-coloured once more when returned to the dark. The best results, however, are obtained when a solution of the epithelium and the rods mixed together is employed. These facts would seem to indicate the existence of a continual intercourse between the epithelium and the rods, the former absorbing fi'om the latter the visual white arising from the action of the light on the visual purple, and by the action of a ferment body (to which the provisional name of Rhodophyllin might be given), reconverting it into visual purple, and returning it to the rods; in the isolated retina, liowever, one must suppose the Rhodophyllin to be present in the rods themselves. Further, one might readily imagine that such a secretory activity of the retinal epithelium would be placed under nervous guidance. But the whole of this part of the subject needs to be elucidated by further researches. Note E. p. 80. Vision without Visual Purple. The facts that visual purple is never present in the cones, that it Ls aV>sent from the macula lutea and fovea centralis, and that some animals (and these not all nocturnal, ex. gr. the pigeon and the fowl) possess no visual purple at all, prove very conclusively that the pre- sence of tills substance is not essential to even the most accurate vision. It is impossible, however, to sujjposc that the changes of the visual purj)lo have no relation wliatevcr to vision; and tlie interesting fjuestion anses, what diflerences in respect to vision can be detected in animals when their visual purple lias been completely bleached as