Researches in colour-blindness : with a supplement on the danger attending the present system of railway and marine coloured signals / by George Wilson.

  • George Wilson
Date:
1855
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Licence: Public Domain Mark

Credit: Researches in colour-blindness : with a supplement on the danger attending the present system of railway and marine coloured signals / by George Wilson. Source: Wellcome Collection.

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    most difficulty, or most liable to be confounded with each other by the Colour-Blind. IV. Extent to which Colour-Blindness prevails in Males and Females. V. Theories of Colour-Blindness. - VI. Advantages and Disadvantages of- Colour-Blindness ; its Prevention and Cure. I.—WNature of Chromato-Pseudopsis or Colour-Blindness. Writing chiefly with a practical end in view, I shall be content to consider colour-blindness as it shows itself in eyes otherwise normal, as of three kinds. 1. Inability to discern any colour, properly so called, so that black and white, z.¢., light and shade, are the only variations of tint perceived. 2. Inability to discriminate between the nicer shades of the more composite colours, such as browns, greys, and neutral tints. 3. Inability to distinguish between the primary colours, red, blue, and yellow, or between these and the secondary and tertiary colours, such as green, purple, orange, and brown. It is to this last variety of colour-blindness that I shall chiefly refer ; but a little must first be said concerning the other two kinds. It will be convenient also, in considering the first and rarest form of colour-blindness, to refer to certain difficulties which attend the examination of all cases of this affection of vision. ‘These difficulties can best be referred to, as they present themselves in those in whom the perception of colour is at zero. Total colour-blindness is very rare, but several well-marked cases of it are on record,’ and it is remarkable that insensibility to colours is not only compatible with distinct vision in other respects, but appears frequently to be attended by a perception of objects very faintly illuminated, such as those sensible to colours do not possess. Perhaps, however, this is only what we should expect; for a retina unfatigued by the impression of colour, will preserve a sensitiveness to faint light such as an ordinary eye, exhausted by the reception of tints of all kinds, cannot retain. In writing this, I do not wish to assert that perfect achromatism has certainly been found in any human organ of vision. None of the recorded cases of total colour- blindness have been examined physically with such care as to war- rant us In saying that it was absolute. With the optical instru- ments now accessible to us, and especially with the means of pro- ducing the purest and most brilliant colours which the apparatus for polarising light secures, we should probably find no human eye otherwise perfect, absolutely insensitive to colour. And even if it were altogether unimpressible by colour, it appears | Taylor’s Scientific Memoirs, 1846. Pp. 162, 163.
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