The most common form of color blindness is, however, that in which only red-green sensations are absent, other colors being distinguishable. There is no disease present in such cases. The defect is hereditary, and consists in deviation from the typical in structure of the retina. The eyes of color-blind persons are as healthy and normal as those of others, in respect to functions other than acting as receptors for certain waves of light. A few cases of blue-yellow color blindness have been reported, these resulting from pathological causes. A color-blind child does not, of course, know from his own experience that he is so. He supposes that everyone sees what he sees, until informed by test or disaster of his deviation from the usual. Color blindness seems to bear no relation to intelligence, so that in drawing where color is used teachers will find a certain percentage of generally very able children producing absurd results. A color-blind child with a great gift for drawing, may succeed in etching or in black and white work of various kinds, as has been shown by the actual rise to eminence of etchers who are color-blind. VI. ILLUSTRATIVE CASES The facts which have been set forth in regard to ability in drawing will be further illuminated by concrete cases. In Figure 19 we have reproduced the psychograph of a child in the elementary school, E 1, showing talent in representative drawing combined with very inferior intelligence. E 1 was a pupil in the sixth grade, at the time when this psychograph was made. She was nearly 14 years old, and therefore distinctly retarded in school status. In spite of her general incompetence, her drawing teacher placed her near the top of her grade in native ability to draw. The child is described as not original. “She can follow better than she can originate.” “Apparently her talent for drawing is inherited. Her father is a tailor. He enjoys drawing and lettering. Her mother takes great interest in the children’s drawings, and an aunt has made paintings of some interest. An older brother of E 1 is reported as very good (original and true) in drawing. She has also two younger sisters and a younger brother who are good in drawing.” Figure 20 shows a copy of a man’s portrait, done by a 14-year-old boy, of IQ near 70. This boy was incapable of normal progress through the school curriculum. Being “left back” repeatedly, he became a truant and otherwise delinquent. His ability for and interest in drawing are highly specialized. Figure 21 shows drawings of movement (not copied) by the same boy. [Illustration: FIG. 19.—Showing the psychograph of a stupid child, who has a special ability in representative drawing. (From Manuel’s _A Study of Talent in Drawing_. Reproduced by courtesy of The Public School Publishing Company.) ]