REPRODUCTION 69 



stances the total number of eggs discharged 

 by a woman in the course of her life would 

 probably be several times four hundred, but 

 the ordinary rule seems to be a single egg at 

 each of the four hundred or more ovulations. 

 You are probably aware that the discharge of 

 the egg is supposed to take place periodically 

 and to be related to menstruation, but if there 

 is an exact relation between these events, it 

 has yet to be discovered. 



As it is the characteristic of the female to 

 produce egg cells, so it is that of the male to 

 produce sperm cells. The human sperm cell, or 

 spermatozoon, as it is commonly called, was 

 discovered in 1677 by Hamm, a student in 

 Leyden, whose master, Leeuwenhoek, gave an 

 accurate description of it. In man each sper- 

 matozoon is a minute, elongated, lashlike body, 

 one end of which is somewhat enlarged. The 

 whole has some resemblance to a much atten- 

 uated tadpole. Each spermatozoon measures 

 ordinarily about one twentieth of a millimeter 

 in length, or roughly a quarter of the diame- 

 ter of the human egg. Its enlarged end cor- 

 responds to the nucleus of a cell, and its lash 

 to the protoplasm, so that the spermatozoon, 

 hke the egg^ is a single cell, though its form 



