On the other hand, so far as this book is an account of the natural history of the genus boy, it may well be an aid to mothers, and to other women who, with no children of their own, are yet concerned for the welfare of adolescent males. If it does not help these to a sympathetic understanding of a boy’s soul, one may at least hope that it will serve to warn them of those regions of it most foreign to their sex. Next to a knowledge of boy nature, comes the knowledge of when to keep hands off and let some man have his chance. To the smaller group of women, mothers and aunts and elder sisters, and especially teachers, who already possess the heaven-sent gift of understanding boys, any assistance may well seem superfluous. Still, intuition may often be supplemented by science. The clearest insight does sometimes fail, and need to be helped out by a more analytical approach from another side than its own. To men, women, and teachers, then, this book,--an ‘apology,’ in a sense, to women, of men who once were boys. Whoever it was that opined that “Men are but children of a larger growth” knew little about boys. The child becomes a youth, and the youth becomes man, by virtue of a process not so very different from that which transforms the caterpillar into a butterfly or the tadpole into a frog. As truly as the caterpillar takes on wings, and the tadpole lungs and limbs, of which neither had any trace before, the child and the boy take on not only habits and instincts and ways of getting on in the world, but actual new structure as well. Boyhood begins with the second set of teeth; it ends with the advent of the beard and a new set of enzymes in the blood. Neither child nor boy nor grub nor pollywog passes on to the next stage of his existence by any mere enlargement. Nor is it altogether true that with the approach of manhood “Shades of the prison-house begin to close Upon the growing boy.” The little child, in his father’s house and under his father’s care, feels the stir of newborn gregarious instincts, and takes his first steps into the larger life of the world. Boyhood proper begins with the rise of impulses which make us citizens and lead us to take care of ourselves; and it ends with the rise of impulses which make us heads of families and lead us to take care of other people. Each step is an enlargement of life. Each transition is marked by a psychic change so profound that it makes the previous narrower condition appear as shadowy almost as a dream, and almost as difficult to recall.