In the boy's body it is another set of structures which are affected at puberty. About the sixteenth year we notice the face begins to change. The hair roots of the beard, which had up to then remained latent, are stimulated, and hairs begin to peer out on lips and cheek. The whole muscular system gains in size and strength ; the bones of the skeleton become thicker and longer, to meet the increased strain of the muscles. The whole apparatus of mastication undergoes a change ; the maxillae and all the bones of the face increase in size and strength ; the muscles of mastication extend their origin on the skull; the bony ridges, which give origin to these muscles, become more pronounced. The ridges which cross the forehead above the orbit are slowly developed, and become more massive and prominent than in the female. The nose assumes its adult form ; its growth is often out of harmony with the rest of the face. The slender, child-like neck, which persists in women, begins to become stouter and thicker in young men. In some this increase in the growth and strength of the neck ceases soon after puberty. Such men retain to some degree the tapering neck and prominent occiput of the boy. In other men the thickness of the neck may continue to increase until the thirtieth year, so that the back of the head appears as if it had been pressed into their stout necks; the occiput, which projected in boyhood, disappears with the age changes of the neck. The heart and the lungs have to respond, in order to meet the increased needs of the muscular and bony systems. The chest expands, especially its lower part; and bit by bit we see the loose-jointed frame of the boy become the closely knit and filled-out body of the mature man. All these changes, we believe, are stimulated, and to some degree regulated, by a secretory mechanism seated in the sexual glands of the male.

One of the most marvellous changes in boys at puberty is the breaking of the voice. The reader is already familiar with the prominence to be seen and felt in the front of the neck, popularly known as " Adam's Apple." On this prominence the finger will distinguish the sharp keel-like projection of the chief cartilage of the larynx—the thyroid cartilage. A notch or hollow can be felt on its upper border, and just above the notch the hyoid bone, which moves with the tongue.

The lower border of the thyroid cartilage cannot be made out clearly with the finger, but about half an inch below it, the anterior hoop of the ring-like cartilage of the larynx —the cricoid—can be felt. Below the cricoid follow the cartilaginous hoops of the windpipe. Now the two vocal reeds or cords, which can be set vibrating with the breath, are fixed within the keel or prominence of the thyroid cartilage by their anterior ends, while their hinder ends are attached to two swivel-like cartilages which are set on the hinder and upper edge of the cricoid cartilage. When we are breathing naturally the vocal cords are drawn apart by special muscles, leaving a triangular interval—the glottis— between them. When we speak the cords are approximated and only a narrow chink separates them. The vocal cords can be tightened or slackened, thus altering the note of the voice. There are special muscles for every movement of the vocal cords. Although singers may not know a single one of these muscles, they can learn to use them, so as to produce what sequence of notes they will. When a boy reaches the age of puberty, all these structures of the larynx—the cartilages, the cords and the muscles, undergo a rapid growth ; the boy's voice " breaks " and becomes hoarse and then manly. It is well known that this change can be prevented, for it was a custom in eastern countries to emasculate choir boys, in order to preserve their voices. In such cases the other sexual characters—the beard, the muscular development, the face, head, neck and body changes were also arrested. One other remarkable change occurred, the limbs, especially the legs, grew to a greater length than in the normal man. Eunuchs are much above the average stature, and they are apt to become fat, for there is no doubt that there is a relationship between the tendency to the deposition of fat, especially on the lower parts of the body, and the activity—or rather non-activity—of the sexual glands in men and women.

These influences of the sexual glands on the growth and form of the human body are of the greatest interest to scientific men, because they seem to afford a clue to the laws which regulate the shape of our bodies. Just as the activity of these glands leads to one set of bodily changes, so it happens, as their activity decreases and their influence is withdrawn, certain parts of the body undergo a further modification. In most women a decided change comes over their features about the fiftieth year. The female sexual glands are then undergoing a down-grade change. Some of these changes, such as the increased wrinkling of the skin and the deepening of natural furrows, are purely effects of age, but the increased prominence of the cheek B bones, the more decided prominence of the supra-orbital ridges, the more massive angles of the jaw and the thickening of the neck, seem to depend on some other factor. There may be a tendency to a straggling growth of hair on the lips and cheeks, and a deepening in the tone of the voice. All these modifications appear to be a mild assertion of male characters—or perhaps it would be more correct to say of neutral or asexual characters, for both man and woman are modifications of a third individual which we may name the neuter or asexual. The withdrawal of the sexual secretion, which restrained the growth of certain parts and helped to preserve the attractions of young womanhood, seem to allow the natural forces of growth to reassert themselves. In men the function of the sexual organs persists to a late period in life, and hence we see no corresponding changes in the opposite sex.

It will be observed that of the two sexes, the male is the more specialized ; the female the least. It is she who retains the characters of youth or of childhood—not only in the face, neck and body, to a much greater degree than the male, but women have also the good fortune to preserve to a greater extent the power of enjoyment of life which is natural to the child. The male has another destiny ; his brute strength and his courage are bought with a price.

It has already been remarked that there is a greater tendency on the part of African races, than is the case with European races, to retain certain child-like characters. This is also true as regards certain sexual characters. The African male, as a rule, shows only a slight growth of hair on the lips and cheeks at puberty. The beard does not sharply distinguish the male from the female. Nor is the female pelvis of the African woman so roomy and capacious as that of European women. Indeed in primitive races there is a tendency for the sexes to approach each other in the pelvic characters.