GENERATION AND DEVELOPMENT. 713 



through the body ; fright causes sensations to be felt in 

 many parts of the body ; and even the thought of tickling- 

 excites that sensation in individuals very susceptible of it, 

 when they are threatened with it by the movements of 

 another person. These sensations from internal causes are 

 most frequent in persons of excitable nervous systems, such 

 as the hypochondriacal and the hysterical, of whom it is 

 usual to say that their pains are imaginary. If by this is 

 meant that their pains exist in their imagination merely, 

 it is certainly quite incorrect. Pain is never imaginary 

 in this sense ; but is as truly pain when arising from 

 internal as from external causes ; the idea of pain only 

 can be unattended with sensation, but of the mere idea 

 no one will complain. Still, it is quite certain that the 

 imagination can render pain that already exists more in- 

 tense and can excite it when there is a disposition to it. 



CHAPTER XX. 



GENERATION AND DEVELOPMENT. 



THE several organs and functions of the human body 

 which have been considered in the previous chapters, have 

 relation to the individual being. We have now to con- 

 sider those organs and functions which are destined for 

 the propagation of the species. These comprise the several 

 provisions made for the formation, impregnation, and 

 development of the ovum, from which the embryo or foetus 

 is produced and gradually perfected into a fully-formed 

 human being. 



The organs concerned in effecting these objects are 

 named the generative organs, or sexual apparatus, since 

 part belong to the male and part to the female sex. 



