On the limitation of physical methods in the investigation of the physiological and psychical phenomena of sight / by F.W. Edridge-Green.

  • Edridge-Green, F. W. (Frederick William), 1863-1953.
Date:
[1900]
Catalogue details

Licence: In copyright

Credit: On the limitation of physical methods in the investigation of the physiological and psychical phenomena of sight / by F.W. Edridge-Green. 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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    &c—are conveyed to the mind through definite perceptive centres. In the case of colour, this perceptive centre is only able to distinguish six definite points of differ- ence (colours) in the spectrum which really presents millions. We, therefore, for the normal-sighted have a hexachromic theory of colour-vision which is in- dependent of light and shade. A hexachromic theory will obviously explain all that can be explained by a trichromic theory. It also agrees with the fact that both blue and violet have been demonstrated to be primary. I may say that I totally disagree with the theory that normal colour vision is trichromic, and am of opinion that the curves and equations which have been constructed to prove that vision is trichromic are mathematically incorrect. I have raised this point as an objection to the Young-Helmholtz theory in a paper recently read before the Eoyal Society. Equal stimulation of the three sets of fibres is supposed to cause the sensation of white light. Red and green when mixed make yellow. Violet and green when mixed make blue. But yellow and blue when mixed make white, which makes one portion of green too many, thus:— E + G = Y, and G + V = B, but Y + B = white, therefore, ,B + G + G + V should equal white, but R + G + V = white. The degrees and varieties of colour-blindness are perfectly explained by the theory of psycho-physical perception. Assuming that the perceptive centre is smaller fewer points of difference are seen. The phenomena of contrasts are explained on the view that colour being a point of difference this becomes more marked on comparison. If we contrast a yellow with a greenish-yellow the yellow inclines to orange and the greenish-yellow to yellow-green. This could not be explained by assuming that the colours differ by the addition of the complementary to each, as the complemen- tary of yellow is blue and this mixed with yellow would make white instead of orange-yellow. In addition to the points which I have already raised the following appear to me as serious objections against the ordinary physical methods of ascertaining the colour per- ception of an individual. Absorption of light by the media of the eye.—Ib is obvious that the media of the eye vary slightly in colour in different persons. This produces a variation of the colour curve in each case without in any way affecting the real colour per- ception of an individual. For instance, a normal-sighted