In about one-fourth of the cases of insanity there is no hereditary predisposition to the disease, and its prevention can be most hopefully looked for in attention to the general laws of health, the observance of which tends to secure immunity from all diseases. In the remaining cases—three times as many, in round numbers—the most hopeful course is in abstaining from marriage altogether or in the avoidance of unwise marriages; and it is an encouraging fact that many people in the community now take that conscientious view of the matter, although if they decide what to do without competent advice they are liable to err in the opposite direction of exaggerating their morbid tendencies, and so increasing their unhealthy predisposition. There are certain groups of physical and mental manifestations which the experienced physician recognizes as signs of tendencies which only await favorable conditions—a sufficient exciting cause—in the indulgence in drink or other excesses, in the exclusive search for wealth or fame, in the absence of healthy occupation, in mental wear and worry, in over-excitement, in the various conditions of ill-health, to develop into actual insanity. This physiognomy of temperament suggests to the observant physician a warning against excess of all kinds, and a recommendation for that course in life which promises the greatest likelihood of preserving a quiet mind and a healthy body and of securing a rational employment. Too much work is less dangerous to most people than too little. States of Mental Defect and Degeneration.[12] [Footnote 12: Compare Moreau's _La Psychologie morbide_ and Morel's _Traité des Dégénérences physiques, intellectuelles, et morales de l'Éspèce humaine_.] MICROCEPHALISM, CRETINISM, INTELLECTUAL IDIOCY, MORAL IDIOCY, INTELLECTUAL IMBECILITY, MORAL IMBECILITY (under which Westphal, Spitzka, and others place moral insanity) are really names for different degrees of similar defects, for the most part hereditary and {139} congenital or resulting from disease or injury in infancy and early childhood, as distinguished from dementia, which is the result of later destructive mental or brain diseases. Idiots and the demented insane are sometimes so alike in their mental condition that, if young persons, they can be definitely distinguished one from the other only by a knowledge of the previous history of the case. Idiocy has its origin at or before birth or soon after, and terminal dementia seldom before puberty, commonly after maturity. In the United States census, where there is a doubt in the matter, the individual is classed as an idiot if the mental disorder occurred before the age of twelve in girls and fourteen in boys, and as insane (demented) if above that age.