168 NERVOUS CORRELATION 



The Reproductive Instinct. — In nearly all kinds of 

 animals reproduction, and therefore racial perpetuation, 

 depends on the fusion of two special sex cells, an egg pro- 

 duced in the ovary of the female, and a sperm produced 

 in the testis of the male (see Chap. XXVI). In order to 

 insure racial perpetuation there must be a definite guar- 

 anty that this fusion will occur. The mechanism for 

 accomplishing it involves correlated muscular movements, 

 which are set in motion and guided, just as are all such 

 movements, through the operation of the nervous system. 

 The correlated movements make up a complex reflex ac- 

 tion, which resembles other reflex actions in being based 

 on sensory stimulation. This stimulation is in part ex- 

 ternal and in part internal, the latter part rising from 

 the organs of reproduction themselves. Chemical regu- 

 lation (see next chapter) is probably a factor also. The 

 combined efi*ect of these influences is to arouse an exceed- 

 ingly powerful emotion fully as strong as any connected 

 either with securing food or with escaping harm. By this 

 emotion the stimuli are vigorously reinforced and the 

 organisms are impelled to reproduce. When one recalls 

 tjjat it is inconceivable that any of the lower animals can 

 or does appreciate the connection between mating and the 

 subsequent appearance of young, the vital biological im- 

 portance of the reproductive instinct is clearly seen. 

 Moreover, should the eff'ect of civilization be to weaken 

 the eff'ects of this instinct seriously in the human race, 

 there would be no effective motivation to prevent the 

 disappearance of mankind from the earth. 



