That _some_ limit to the indulgence of natural instinct is necessary in both sexes will be evident from the early age at which the sexual movement commences, as well as from the length of time required for its completion. It is not only in children of twelve and fourteen that this instinct is already strongly marked, it may be observed at a much earlier age. Numberless instances of juvenile depravity come under the observation of the physician, and such gross cases are only exaggerations of the refined instincts veiled by modesty and self-respect, which are gradually growing in all healthy children. That this mental instinct tends to express itself in the unformed bodies of children corrupted by evil example, we have only too abundant proof. A chronic evil of boarding-schools, of asylums, and of all places where masses of children are thrown together without wise moral supervision, is the early habit of self-abuse. Long before the boy or girl is capable of becoming a parent, this dangerous habit may be formed. It is not necessarily the indication of a coarse nature. It is observable in refined, intellectual, and even pious persons, as a habit carried on from childhood, when it was begun in ignorance, or taught, perhaps, by servants, or caught from companions. Many a fine nature in both man and woman has been wrecked, by the insidious growth of this natural temptation, into an inveterate habit. The more common result, however, of this vicious practice is a premature stimulation of the sexual nature, which throws youth of both sexes either into habits of early licentiousness or into a morbid condition of mental impurity. An experienced physician[33] writes: ‘The earliest and most frequent cause of disorder of the generative apparatus is the practice of self-abuse, the tendency to which is strongest about the age of puberty.... Excitement is increased by the conversation and thoughts which are indulged in, and it is apt to be unchecked by the moral control which has not yet acquired its proper influence. Moreover, lads are often induced to the pernicious practice by their companions, who may be as ignorant as themselves of the wrong and mischief they are doing. It would be a very good thing if those who have the charge of boys were less scrupulous in giving warning upon this matter. Much trouble and anxiety might be spared by timely advice seriously and kindly given.... An extensive acquaintance, through years with those who have just come from our schools, has impressed the importance of this matter upon me.’ Dangers thus existing which may threaten the youngest child, the necessity of guidance, the formation of good habits, and the inculcation of self-respect even in childhood is evident. At an early age self-control can be taught. It is a principle which grows by exercise. The more the brain asserts its power of Will over the automatic actions of the body, the stronger may become the control of reason over sensations and instincts.