As already pointed out in the chapter on Heredity and Atavism, the arrests of development may affect one side of the body, while the other pursues the direct course of development. This may show itself in over-growth, as well as in under-growth, on the affected side. The person may appear, even from the centre of the forehead down, as if the halves of the bodies of two different persons had been joined in one. Conditions may vary from this extreme type to a state in which a lack of proper nerve and blood supply on the undeveloped side predisposes to attacks of disease, as already pointed out. Not rarely does it happen that acromegaly attacks the side most deficient in nerve supply. The same is true of allied disorders affecting the growth of the muscles. The conditions of development may be such that both sides are equally defective in nerve supply, so that when acromegaly occurs it may attack both sides equally. This is particularly apt to be the case with the lower extremities, and enlarged feet (Fig. 105) are not an uncommon result. [Illustration: FIG. 106.] The feet, in addition to the condition already described as being common in both extremities, exhibit special stigmata of their own in consonance with the evolutionary advance which the foot has shown as compared with the hand in man's evolution. In the lower races the hollow of the foot does not exist, and the condition known as flat-foot occurs (Fig. 106). This is usually associated with low instep. It occurs among the stigmata of degeneracy, and is not rarely associated with grave moral defects and intellectual distortions. It and other feet degeneracies have been found frequently among paranoiacs, moral imbeciles, and prostitutes. This is particularly true of the prehensile power of the foot.[235] CHAPTER XV DEGENERACY IN REVERSIONAL TENDENCIES The hair of the head and body may never develop from the condition of down (lanugo) present in the new-born. The hair over the sexual organs may alone remain in this condition, not showing itself at puberty. In women the hair may be unusually developed on the face and chest. It may also cover the whole body, a condition which is normal in the Ainus of Japan. It may develop, as already shown, very markedly in the lumbar regions.