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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    striking was its appearance after it had lain twenty-four hours in alum. The posterior surface of the retina of the eye which had been exposed during death exhibited the most complete image of the window, with two rows of square panes sur- mounted by a semilunar space, all white on a red ground, with sharp red crosses. The image began at the red line of par- tition of the retina, and shewed in its lower part strong per- spective foreshortening, especially of the upper row of panes and of the arch. Since the head had been laid in a natural position, resting on the lower jaw, the upper part of the window would of course be reflected into the lower part of the eye, just as it appeared in the image. The strong foreshort- ening in the figure is intelligible when the distances of the lower and upper window-edge from the eye are borne in mind, and an albino eye, which for the sake of comparison was placed in the same position in reference to the window, exhibited an image of exactly the same character, and so afforded a corrobo- ration of the correctness of the optogram. The experiment shewed at the same time in a very striking manner what excellent optograms may be present in the layer of the rods without their being visible when the retina is looked at from the front. For in this albino eye, when the retina was simply everted, though the most beautiful purple colour could be seen on it, no difference of tint could be re- cognized which would enable one to infer the existence of an image, certainly at least not of so sharp and large an image as really existed there. In the case of the first eye, which had been exposed to light during life, the posterior surface of the retina shewed in the experiment no regular optogram, but only a hardly per- ceptible spotty bleaching, leaving it a matter of doubt whether it corresponded in size and arrangement to the image which had been formed po.st mortem in the other eye. The intensity of the light of the dull sky remained the same as far as the eye could judge in both experiments. The weather indeed wa.s as bad as possible, therefore all the more suitable for Bhewing the ditferencc between an intra vitam and post mortem action of light. The reason why the optograpliy was unsuc-