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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    During my first attempts to test the truth of Boll's state- ments, I was under tlie impression, strengthened by what Boll had said, that the greatest haste was necessary in removing the eye, and taking out the retina; but I very soon convinced myself that a considerable time may be allowed for the ope- ration, since the visual purple, as I call the proper colour of the retina, may continue to exist for some time after the retina has ceased to be in a physiologically fresh condition, and even - after death is only destroyed by light. Under the light of a good gas-lamp the retina may be quite leisurely spread out, and is then seen to lose its colour very gradually, for what takes place under bright daylight in half a minute, lasts in this case from 20 to SO minutes, that is to say, much longer than Boll gives as the duration of tissue-life. And in the dark, or in the light of a sodium flame, the purple does not pass away at all, either in the frog or rabbit, at least not for 24 or even 48 hours, in spite of decomposition evidently set- ting in. By the discovery of these facts, the path of experimentation with the visual purple is freed from many difficulties. The necessary preparations can be conducted leisurely in a dark chamber lighted by a sodium flame, and the object then brought out for examination into diffuse daylight. A room such as is used by photographers, into which the light passes through yellow glass or paper, answers the same purpose, but less perfectly. As w^e do not exactly know how long the rods or their parts remain alive after death, I treated the retinas of frogs in the sodium chamber with the most various reagents, many of which were without doubt capable of producing great structural alterations, to see whether the colouring and sensibility to light were thereby affected. The colour was destroyed by heating to lOO*' C, by alcohol, by glacial acetic acid, by soda solution, both concentrated, and 10 per cent. It was not affected by a solu- tion of sodium chloride 05 per cent., by strong ammonia, by sodium carbonate solution, by saturated sodium chloride solu- tion, by alum, lead acetate, acetic acid 2 per cent,, or tannic acid 2 per cent., by lying in glycerine for 24 hours, by ether, or