Color perception : normal and subnormal / by Charles A. Oliver.

  • Oliver, Charles A. (Charles Alexander), 1858-1932.
Catalogue details

Licence: Public Domain Mark

Credit: Color perception : normal and subnormal / by Charles A. Oliver. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    Thomson, constitute the majority of the devices that have been successively championed and upheld by their individual contrivers. The more or less fixity of the tests, thus limiting the number of colors from which a choice might be taken; the arbitrary relation- ship of the component parts without any scientific reason, thus allow- ing them to fail to express the many percentages of lowered color- vision presented by the different candidates for examination, and permitting numbers of persons affected with subnormal color per- ception to escape by reason of the confusion, colors not being equal to the exact amount of the resident color error; as well as the lia- bility of the methods to become known and understood, and thus rendered practically worthless when pursued among a great number of similarly placed individuals, are some of the main reasons why these latter plans cannot be satisfactorily employed. Another plan by the same method is the placing of colored pow- ders in homoeopathic vials as pursued by Mauthner and Cohn. This has been done in order that the candidate shall not be able to dif- ferentiate color changes in yarns, worsteds, and wools by the sup- plemental use of the senses of touch and smell. That the objections these authors offer to the free handling of colored wools is in meas- ure true there can be no doubt; a fact that as long ago as 1849 was pointed out by Wartman, who made mention of a man with well- marked subnormal color perception, who “ corrected by the help of touch a part of the erroneous judgments which he formed regarding colors.” This power of the possessor of subnormal color perception was reproven only six years later by Wilson, who justly attributed it to a delicacy of the tactile sense in discriminating between the harsh- ness and the smoothness of variously colored dyes, and said “ a wool dyed with a mineral green might thus be distinguished by the touch from one dyed with a vegetable, although the color-blind eye could detect no difference between their tints.” The second method (direct comparison of spectral color) unfor- tunately cannot be brought into every-day employment as an ordi- nary test for the quick detection of lowered color sense, although it can be made to serve a useful purpose in cases requiring more than ordinary observation, as among persons under judicial action. The apparatus is expensive; its mechanism is complicated and liable to become disarranged; both the examiner and the candidate must possess the necessary intelligence to handle the instrument; and the