A CHAPTER FOR MARRIED PEOPLE 505 



have seen to belong to most of the other vital phe- 

 nomena. ' ' 



Periodical Reproduction.— "In most of the lower 

 orders of animals there is a periodical development 

 of the testicles in the male, corresponding in time with 

 that of the ovaries in the female. As the ovaries en- 

 large, and the eggs ripen in the one sex, so in the other 

 the testicles increase in size, as the season of reproduc- 

 tion approaches, and become turgid with spermatozoa. 

 The accessory organs of generation, at the same time, 

 share the unusual activity of the testicles, and become 

 increased in vascularity, and ready to perform their 

 part in the reproductive function." 



"Each of the two sexes is then at the same time 

 under the influence of a corresponding excitement. The 

 unusual development of the genital organs reacts upon 

 the entire system, and produces a state of peculiar 

 activity and excitability, known as the condition of 

 'erethism.' " 



A Lesson from Instinct.— "It is a remarkable 

 fact, in this connection, that the female of these animals 

 will allow the approaches of the male only during and 

 immediately after the cestral period ; that is, just when 

 the egg is recently discharged, and ready for impreg- 

 nation. At other times, when sexual intercourse would 

 be necessarily fruitless, the instinct of the animal leads 

 her to avoid it; and the concourse of the sexes is ac- 

 cordingly made to correspond in time with the maturity 

 of the egg and its aptitude for fecundation." 



"The egg, immediately upon its discharge from the 

 ovary, is ready for impregnation. If sexual inter- 

 course happens to take place about that time, the egg 

 and the spermatic fluid meet in some part of the female 

 generative passages, and fecundation is accomplished. 



