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.

    269/346 (page 241)
    CHAPTER XXII. ]METHOD OF DECmiN-G THE PEECISE AMOUNT OE COLOK-BLESTDNESS BY HOLMGEEN's CHKOMA- TOSKIAjNIETEE, OE COLOE-SENSB testes. — PEO- FESSOE DONDEES'S IVIETHOD OF DETEEMINING QUANTITATIVELY COLOE-PEECEPTION. One of the additional methods of detecting color-blindness is of value for examiners to be acquainted with. It is based on the true principle of comparison, no names of color being required of those examined. It also, like the method of Bonders, enables us to express in figures the amount of the chromatic defect in each individual case. The apparatus is arranged to enable us to use colored shadows. It is not very expensive, and can be used by day or night. To further test railroad employes or others, after having decided on their color-blindness by Holmgren's worsteds, it will be, as I said, of great value to examiners, and also serve the purpose of physiological experi- menters. It has the advantage of giving constant results independent of the examiner. These results can be readily understood by the laity, and the test applied before them. As Professor