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

  • Kuhne, W, 1851-1930.
Date:
1878
Catalogue details

Licence: Public Domain Mark

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

Provider: This material has been provided by UCL Library Services. The original may be consulted at UCL (University College London)

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    I been able to perceive even slight indications of red colouring in the rods of the bat, which are certainly very minute, and which, as is well known, do not surround any cones. I must therefore maintain that the rods in this species which I have examined are colourless, even if colouration should really be proved to exist in other species of this great order where the rods are longer. Without wishing to say that genuine rods which are not red are altogether useless for vision, it appears to me doubtful on account of their mere existence in the bat to infer a power of sight, at all events one at all comparable to our own sense ; since we know from Spallanzani's famous experiment, which Briicke in his Vorlesungen iiber Physiologie justly interprets from the stand-point of the knowledge of the , present day, that these animals shew no awkwardness in their ' movements after their eyes have been destroyed. With the same right that we conclude from the behaviour of blinded bats that they possess an astonishingly fine sense of touch and sensitiveness to rays of heat and the like, we may also conclude, that they are certainly not accustomed to sight in any manner of which we have experience, and indeed have no need of it. The difference between their vision and ours may be almost as great as that between the sense of smell in sporting dogs and in a human creature. But it is intelligible that in cases where other peculiarly finely developed senses render a more acute vision unnecessary, that there may yet exist a morphological visual apparatus which is fairly well constructed, but yet is deficient in one of the chemical con- stituents which are sensitive to light. It seems preferable to ascribe to the bat four senses only, rather than six, as our predecessors wished to do. Another animal that especially lives in the dark, namely the badger, whose eye in relation to the size of its head and body must be called small, exhibits a well-developed purple in the retina. I received the animal alive, placed it for three hours in the dark, and immediately prepared the eye in sodium light. The retina bleached quickly in light, passing 1 Wien, 1875.