Other effects of the nutritive disturbances produced by school strain are local irritations about the sexual organs. These may arise from irritation by uric acid of the mouth of the bladder in boys, or of the vagina and bladder in girls. Neurotic persons are liable to nerve storms, which express themselves in emotional displays or restlessness or nagging tendencies. These often coincide with the uric acid tendency to express itself in "storms," like other periodical phenomena of the nervous system. In consequence, "sexual storms" result in neuropaths, whether the neuropathy be inherited or acquired. Local genital organ irritation leads to scratching. From this are produced "masturbation storms," which the subject loathes but cannot control. These occur also from the direct effects of constipation, as well as from the worms and other parasites which constipation fosters in the bowel. Teachers, by compelling children to retain urine through fear of masturbation, often lead to what they intend to prevent. At the outset masturbation and sexual explosions are often a physical expression of school strain destitute of moral significance. They are removable by removing the school strain and its consequences. If strengthened by protracted existence they intensify degeneracy due to school strain. The states of imperfect nutrition, resultant from nerve strains on gland function, in this way and in others, interfere with the proper evolution of puberty and the involutional changes at the "change of life," which occurs in both sexes. The conditions of "nervous cough," of so-called "catarrh," and its ally, bronchorrhoea, are often found as expressions of the systemic exhaustion from school strain, and are treated as purely local conditions. School strain, therefore, produces, like all the acquired factors of degeneracy, a systemic nervous exhaustion which may be expressed either in general neuropathy or hysteria after puberty, or in the tropho-neuroses, like gout and allied states, or in epilepsy or arterial change, predisposing to rupture of arteries at periods of stress, with resultant convulsions and paralysis. CHAPTER X THE DEGENERATE CRANIUM The cranium or skull is a development in part of the vertebræ or bones forming the backbone, and in part of dermal or membranous bones, which of old in reptiles, as in the alligator to-day, formed the protective armour of the skin of the head. As the head end of the spinal cord of the lancelet developed, the cartilage enclosing it developed to protect it. This was the earlier evolution. Later, another skull developed in connection with this. The cranium or skull therefore has, as Minot remarks,[188] a double origin, or, rather, there are two skulls which were originally distinct. In evolution from the lowest fish to the highest mammal, and in the embryonic development of man, these become united.