perceptions are the result of three primary effects in the eye, namely, red, green and violet, rather than on any analytical classification of actual experiments concerning color blindness. Color tests should be so arranged as to detect either a defect in the brain which renders it difficult for the pupil to remember the names of the several colors, or in the eye, by which he cannot see a difference between two dissimilar colors.
A person totally color blind would see in the solar spectrum a band of gray in various tones, and hence if a red and a green should seem to be of the same tone of gray he would call both either red or green, and after much experience would come to give color names to various tones of gray.
Such cases, however, are exceedingly rare, if in fact they exist. Other scientists and physiologists have doubted the truth of the claims made by both Holmgren and Helmholtz, and some have made extended experiments regarding color blindness which seem to oppose the Holmgren theory. In view of these conditions it does not seem necessary for a teacher in the elementary grades to attempt to grasp the situation very fully, and much less to aid in the solution of the problem. Very fortunately this is unnecessary, because in all the scientific tests proposed for adults nothing is accomplished which any primary school teacher will not be easily able to determine during the first two or three years of ordinary school work, if the modern system of color instruction is pursued.
There is no better material than colored papers for testing the color perceptions, and the exercises of selecting, matching and arranging the spectrum colors by means of the small color tablets generally in use in the first years of school are the very best that can be devised without regard to any of the abstract theories concerning either the cause or the possible classification of color blindness.
For some reason the most common form of color blindness occasions a confusion between red and green, as for example, we are told, by some people, that in picking wild strawberries in
