70 BIOLOGY AND SOCIAL PROBLEMS 



at first sight is not so suggestive of this com- 

 parison. 



The testes in man produce spermatozoa 

 more or less continuously from the beginning 

 of puberty, at about the fifteenth year, on to 

 old age. Spermatozoa are often absent in old 

 men, but they have been found in individuals 

 as late as the ninetieth year. It has been esti- 

 mated that in the period of thirty years be- 

 tween the twenty-fifth and the fifty-fifth year 

 of manhood, one individual will produce the 

 prodigious number of 339,385,500,000 sper- 

 matozoa, a number incredibly large compared 

 with the egg cells probably liberated by the 

 normal woman during her sexually active life. 



When the human egg cell is fully formed, 

 it is discharged on the surface of the ovary, 

 whence it makes its way down the Fallopian 

 tube toward the uterus and the exterior. If it 

 is not fertilized, it disintegrates and is lost, 

 but if copulation has occurred and sperm cells 

 abound in the tube, one may enter the egg 

 and thereby fertilize it. The fertilized egg then 

 passes down the Fallopian tube into the uterus, 

 where, instead of disintegrating, it attaches it- 

 self and develops into an embryo and eventu- 

 ally into a fully formed child. 



