On the physiological action of light : abstract of three communications read before the Royal Society of Edinburgh / by James Dewar and John G. M'Kendrick.

  • Dewar, James, Sir, 1842-1923.
Date:
[1873?]
Catalogue details

Licence: Public Domain Mark

Credit: On the physiological action of light : abstract of three communications read before the Royal Society of Edinburgh / by James Dewar and John G. M'Kendrick. Source: Wellcome Collection.

Provider: This material has been provided by The University of Glasgow Library. The original may be consulted at The University of Glasgow Library.

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    sensitive to light; and c. When light was allowed to impinge on both eyes, while the one pole was in contact with either eye and the other with the left optic lobe, the result was nearly double that produced by the impact of light on one eye alone, either right or left. These effects may be explained by the decussation of the optic nerves in the optic commissure. 5. The eye of a snake1 was examined, and in its action resembled tha.t of the frog. 6. We are therefore now in a position to state, that the law of the variation in the electro-motive force of the retina and optic nerve, holds good in the following groups of the animal kingdom, Mammalia, Aves, Reptilia, Amphibia, Pisces, and Crustacea. 7. Many experiments have been made which prove that the psychophysical law of Fechner, alluded to in previous com- munications, is not dependent only on perception in the brain but in part on the structure of the eye itself. The effects which occur on, during, and after the action of light on the retina, also take place after the eye has been removed from all connection with the brain. Thus the law of Fechner, is not, as has been hitherto supposed, a function of the brain alone, but is really a function of the terminal organ, the retina. 8. We have also employed a new method of registering galvanometrical variations, which may be of service in many physical and physiological researches. This consists in placing at the proper distance from the galvanometer, instead of the ordinary graduated scale, the surface of a cylinder covered with paper, and moving on a horizontal axis by clock-work. The spot of light reflected from the galvanometer mirror is rendered more precise by having the shade of the galvan- ometer lamp blackened over the entire surface, with the excep- tion of a spot about three millimetres in breadth, in the centre of which a line or cross is made of soot. The image of this line 1 Kindly sent us by Mr Bartlett, of tbe Zoological Gardens, Regent’s Park. We have also to acknowledge the kindness of Mr Lloyd, Manager of the Crystal Palace Aquarium, who supplied us with three specimens of Eledone (a cuttle-fish, to represent Mollusca), but none arrived alive.
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