Color-blindness : its dangers and its detection / by B. Joy Jeffries.

  • Benjamin Joy Jeffries
Date:
1879
Catalogue details

Licence: Public Domain Mark

Credit: Color-blindness : its dangers and its detection / by B. Joy Jeffries. Source: Wellcome Collection.

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    order, or in a definite order in accordance with their simi- larity. Thus they may be grouped according to the color- perception of the normal-eyed or the color-blind, and, in the latter case, in different groups corresponding to the different forms of color-blindness. The grouping of colors which I proposed was on this prm- ciple, and it is printed in the 'Nordst Medicinskt Arkiv.,' 1874, and carried out in the plate published with this book. The plan is a good one where we are dealmg with educated and intelligent people, and many color-bUnd may be thereby detected. To be at all complete, and generally practical, this method must have a much larger number of shades. Experience shows that the color-blind is often un- certain as to the similarity between two colors, depending less upon the color than on what to him is the most impor- tant distinguishing mark; namely, the intensity of the hght, or the degree of saturation. And, as to equal intensity ot two colors whose similarity he would find, he is so particular, that the test may be just too much or too little. We must add that all color-blind of the same class are not as particular as to intensity of light or degree of saturation; and, moreover, it is impossible, on plates which are multiplied, to get exact- lY the necessary colors, whilst the price increases with the number of colors. The difficulties were therefore enough for us to abandon this method. The worst is, however, that the supposed gain in time is more than counterbalanced by lack of conveniences and other difficulties. In short, the loss is greater than the gain. , .r,- These remarks hold good, not only in reference to th]5 form of test proposed by me in 1874, but also to all colored tables which have so far been published. A proof is the worked worsteds of Dr. Daae, and the repeated attempts of Dr Stilling to construct colored plates. As is known, neither have succeeded in solving the difficulties, although careful and ingenious attempts have been made to conquer some of those I have spoken of. These tables, from the very nature of the subject, can only have a limited employ- ment as an addUional test, but are for the exammation of masses wholly unserviceable. Experience has perfectly proved this to me, and will the same to every expert, ihe new editions, unfortunately, are not changed m this respect.