Abstract
NEW Method of Experimenting.—One of the chief difficulties in arriving at the exact relation between the electrical variation and the luminous and colour intensity of light, was the continuaLy diminishing sensibility to the stimulus, owing to the abnormal conditions of the eye when removed from the head. When the experiment begins, the eye is remarkably sensitive to light, and a large variation of current is obtained; but the amount of this current is gradually falling, in consequence of the gradual change in the parts of the eye, owing to their loss of vitality and sensibility. In fact, the parts are dying—the blood is not circulating, and molecular and chemical changes are slowly occurring. In the case of the frog however, it is a fact that the retina retains its sensibility from three to four hours, and sometimes longer. After a lapse of two hours the frog's eye frequently remains in a tolerably stable condition, in which it d oes not lose sensibility rapidly. This condition may last for four or five hours. In order to get rid of the difficulty of gradual death of the parts, various methods were tried in earlier experiments in the attempt to remove the eye as quickly as possible, and to make the observations rapidly. In the case of the warm-blooded animals this did not lead to good results, because the sensibility to light disappeared in a very few minutes. On several occasions the posterior aspect of the eye was exposed in the living anæsthetised warm-blooded animal, and on bringing one electrode into contact with the severed optic nerve while the other touched the cornea, the observations were tolerably constant. This method was troublesome and difficult.
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The Physiological Action of Light 1 . Nature 15, 433–435 (1877). https://doi.org/10.1038/015433a0
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DOI: https://doi.org/10.1038/015433a0
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