REPRODUCTION 583 



increase in size; fully formed seminal fluid is secreted, and erec- 

 tions of the penis occur. As these changes are completed spon- 

 taneous nocturnal seminal emissions take place from time to time 

 during sleep, being usually associated with voluptuous dreams. 

 Many a young man is alarmed by these; he has been kept in ig- 

 norance of the whole matter, is too bashful to speak of it, and 

 getting some quack advertisement thrust into his hand in the 

 street is alarmed to learn that his strength is being drained off, 

 and that he is on the highroad to idiocy and impotence unless 

 he place himself in the hands of the advertiser. Lads at this 

 period of life should have been taught that such emissions, when 

 not too frequent and not excited by any voluntary act of their 

 own, are natural and healthy. They may, however, occur too 

 often; if there is any reason to suspect this, the family physician 

 should be consulted, as the healthy activity of the sexual organs 

 varies so much in individuals as to make it impossible to lay down 

 numerical rules on the subject. The best preventives in any case 

 are, however, not drugs, but an avoidance of too warm and soft 

 a bed, plenty of muscular exercise, and keeping out of the way of 

 anything likely to excite the sexual instincts. 



In the woman the pelvis enlarges considerably at puberty, and, 

 commonly, more subcutaneous adipose tissue develops over the 

 Body generally, but especially on the breasts and hips; conse- 

 quently the contours become more rounded. The external genera- 

 tive organs increase in size, and the clitoris and nympha3 become 

 erectile. The uterus grows considerably, the ovaries enlarge, some 

 Graafian follicles ripen, and menstruation commences. 



Hormones of the Reproductive System. The interrelations of 

 various processes in the functioning of the reproductive mechan- 

 ism are many of them very striking and they have long been the 

 subject of investigation. The development of the so-called second- 

 ary sexual characters at puberty, where in a few weeks the vocal 

 cords change and hair develops over various parts of the body, is 

 a good example of the sort of interrelations that occur in this sys- 

 tem. The fact, known for centuries, that castration in early life 

 prevents the appearance of the secondary sexual characters, shows 

 that they are directly dependent on the reproductive organs. Be- 

 fore the idea of hormone action had crystallized to its present form 

 some such mechanism had been postulated for the reproductive 



