When the upper jaw is normal, or smaller than the lower, the extent of the posterior portion is determined by the occlusion of the first permanent molar, which keeps the alveolar processes in permanent relation to each other at this point and allows freedom of development in front. If the occlusion be not normal, the upper jaw and alveolar process will develop laterally as well as anteriorly. The teeth of the anterior columns may either stand vertically, or they may be turned in toward the lower incisors. The latter defect is produced by the action of the lips. When the cuspids are in their normal position the upper incisors form a larger arch than the lower, and this permits of their being turned inward; but when the cuspids have moved so far forward that they are not normally interlocked with the lower teeth, the incisors are too crowded to permit this. While the jaws are growing smaller the teeth tend to cause reversion to the original form. Arrest of development of the superior maxilla is always associated with marked depression at the alæ of the nose, producing the appearance of having been hollowed out from a point at the floor of the orbit to the grinding surface of the lower teeth (Fig. 94). [Illustration: FIG. 95.] Arrest of the lower jaw (Fig. 95) is common among degenerates. This consists of a shortening of the body of the jaw. Sometimes it is arrested to such an extent that there is apparently no chin. About 50 per cent. of criminals of Elmira, New York, have this deformity. The following table shows the number of deformities of the jaws and teeth which I have found among some of the degenerate classes.