Youth and Sex

Probably the most important years in anyone's life are those eight or ten preceding the twenty-first birthday. During these years Heredity, one of the two great developmental factors, bears its crop, and the seeds sown before birth and during childhood come to maturity. During these years also the other great developmental force known as Environment has full play, the still plastic nature is moulded by circumstances, and the influence of these two forces is seen in the manner of individual that results. This time is generally alluded to under two heads: (1) Puberty, (2) Adolescence. By Puberty we understand the period when the reproductive organs are developed, the boy or girl ceasing to be the neutral child and acquiring the distinctive characteristics of man or woman. The actual season of puberty varies in different individuals from the eleventh to the sixteenth year, and although the changes during this time are not sudden, they are comparatively rapid.

By Adolescence we understand the time during which the individual is approximating to the adult type, puberty having been already accomplished. Adolescence corresponds to the latter half of the developmental period, and may be prolonged even up to twenty-five years. CHAPTER I. CHANGES OBSERVABLE DURING PUBERTY AND ADOLESCENCE IN GIRLS. 1. Changes in the Bodily Framework.—During this period the girl's skeleton not only grows remarkably in size, but is also the subject of well-marked alterations and development. Among the most evident changes are those which occur in the shape and inclination of the pelvis. During the years of childhood the female pelvis has a general resemblance to that of the male, but with the advent of puberty the vertical portion of the hip bones becomes expanded and altered in shape, it becomes more curved, and its inner surface looks less directly forward and more towards its fellow bone of the other side. The brim of the pelvis, which in the child is more or less heart-shaped, becomes a wide oval, and consequently the pelvic girdle gains considerably in width. The heads of the thigh bones not only actually, in consequence of growth, but also relatively, in consequence of change of shape in the pelvis, become more widely separated from each other than they are in childhood, and hence the gait and the manner of running alters greatly in the adult woman.