PUBERTY AND MENSTRUATION 429 



for body-material and for relative passivity, while the spermatozoon is 

 the supplier of the activity and the energy by which alone the body- 

 matter becomes spontaneously motile and, in short, alive. Both aspects 

 of the actual animal are essential, a material body and the activity 

 whereby that organized material may adjust itself to its environment. 



The cellular reproduction of man, as of all other mammals, takes place 

 by mitosis (karyokinesis), as distinguished from the amitosis or direct 

 cell-division of many protozoans and some metazoans. An outline 

 of the mitotic process was given in the chapter on Protoplasm (see 

 page 45). 



PUBERTY AND MENSTRUATION. 



Our first inquiry must be as to how the reproductive apparatus is 

 made ready for use in the developing adolescent, especially in the girl, as 

 a preliminary to a description of that use the fertilization of the woman 

 by the man. Here, as in the other functions, a detailed knowledge of the 

 genital apparatus of each sex, to be obtained from anatomy, is presup- 

 posed. 



Puberty in the Male. From the beginning of voluntary control during 

 the latter part of the first half-year of extra-uterine life the boy-baby 

 shows in some slight respects his functional difference from the girl- 

 baby he has especially more tendency to the initiative and is on the 

 average bolder in his activities. None the less, up to the age of twelve 

 or fourteen the nature of the boy is like that of the girl in a much greater 

 degree than ever again it can normally be. Many perfectly normal girls 

 up to this age and sometimes beyond it do boyish things, and vice versa. 

 It must be deemed physiologically a distinct advantage to both sexes 

 that the boys and girls should mingle freely and naturally up to the age 

 of twelve and freely also, if not quite naturally, beyond that time. Such 

 association keeps the boy from becoming, sometimes, a "boor," and the 

 girl from becoming a prude. 



When about fourteen or sixteen years of age, in temperate climates, 

 the boy's organism begins to change and with it his mental nature more 

 or less, although to a much smaller degree perhaps than in case of the girL 

 The testicles rapidly increase in size and become more pendulous and 

 the dartos tunic more contractile. The penis grows in length and soon 

 develops in its cavernous bodies an increased power of erecting, while 

 the prepuce becomes more easily removable over the glans. The vocal 

 cords develop and elongate especially, and during these changes are apt 

 to be badly controlled in speaking. The shoulders broaden and hair 

 grows on the lower part of the face, in the axilla, and on the lowest middle 

 part of the abdomen, over and around the penis. The moral sentiments 

 become more conspicuous in the nature of the boy, and beauty especially 

 becomes for the first time a reality to him. Around his whole being 

 floats a consciousness of new powers, new interests, and new life, for 

 this sexual flood-tide pervades without his realizing it perhaps every 



