Page:Popular Science Monthly Volume 83.djvu/154

150 feet development of them. A defective child goes through the stages of its development more slowly than the normal child, and fails to reach the later stages. Such a child has not a different heredity from the normal child, but simply a less complete expression of it. If this is true, defects measure environmental control. Every defect has some objective cause which acts as a check on normal growth. We make progress, therefore, in the study of defects as we connect them with bad environments.

We can thus detect physical defects. To ascertain and measure mental defects the needed criterion is found in the law of the association of ideas. If a mental defect has at its basis a harmful association of ideas, we may confidently affirm that its origin is environmental. AU ideas are postnatal, and hence all associations must be formed after birth. We do not need a biologic character to create a new association of ideas, but only some reorganization of experience. In harmony with these facts and principles there should be four stages of child development, which appear in the following order:

 1. The elementary life stage. 2. The sensory stage. 3. The stage of bone formation. 4. The motor stage.

On the basis of this analysis, there should be a type of man who has the elementary vital functions, but lacks the later organic developments. That such a type exists can be shown, and its indices readily pointed out. This type has high cheek bones, a sloping forehead, a flat, broad nose, and a defective lower face and chin. The central part of the face is fully developed, while its upper and lower parts are imperfect. The people of this type are short in stature, broad at the hips, and round-headed. All the vital functions are normally developed, but the later stages of growth are defective. Such people thrive in a simple environment, especially if they have a pictorial religion and a conventionalized morality.

A second physical type is also easily described. Here the upper part of the head is fully developed, and the central part of the face is defective; the nose is peaked and narrow at the base; the teeth are bad; the mouth is small; and the chin is pointed. This physical description has a meaning that can be readily interpreted. The retardation has taken place late in pregnancy after the brain has passed through its initial development. A child's face lengthens downward as the child matures. A weak, short lower-face indicates, therefore, a stoppage of growi;h after the middle-face and upper-face have been formed. A person of this type is likely to be short and thin and have a poorly developed bone structure. The type is usually regarded as intellectual when contrasted with the first type, which is often designated as sexual.