Routine examinations of the sense of color are becoming increasingly important both in connection with occupation in peaceful pursuits and in relation to the national defense. As often as not, a test of color vision must be made when a large number of examinees is present. Any reliable method of testing a sizable group at one time will confer an obvious boon and will naturally be applicable in situations in which a color vision test, though desirable, has not customarily been given because of lack of time or of sufficient examiners.
An exact diagnosis of a given deficiency in color vision can be made only with a Nagel anomaloscope in the hands of an expert. But for practical purposes it usually suffices to be able to say "deviation from normal trichromatic vision—unfit for special service." Such a diagnosis can be made simply and with a minimum of error with Stilling