726 GEKEEATION AND DEVELOPMENT. 



Graafian vesicles being found ruptured in the intervals of 

 the periods of heat ; and that female animals do not admit 

 the males, and never become impregnated, except at those 

 periods. 



Many circumstances make it probable that the human 

 female is subject, in these respects, to the same law as the 

 females of other mammiferous animals ; namely, that in 

 her as in them, ova are matured and discharged from the 

 ovary independent of sexual union, and that this matura- 

 tion and discharge occur periodically at the epochs of 

 menstruation. Thus Graafian vesicles recently ruptured 

 have been frequently seen in ovaries of virgins or women 

 who could not have been recently impregnated, and 

 although it is true that the ova discharged under these 

 circumstances have rarely been discovered in the Fallopian 

 tube,* partly on account of their minute size, and partly 

 because the search has seldom been prosecuted with much 

 care, yet analogy forbids us to doubt that in the human 

 female, as in the domestic quadrupeds, the result and 

 purpose of the rupture of the follicles is the discharge of 

 the ova. 



The evidence of the periodical discharge of ova at the 

 epochs of menstruation is first, that nearly all authors who 

 have touched on the point, agree that no traces of follicles 

 having burst are ever seen in the ovaries before puberty 

 or the first menstruation ; secondly, that in all cases in 

 which ovarian follicles have been found burst, indepen- 

 dently of sexual intercourse, the women were at the time 

 menstruating, or had very recently passed through the 

 menstrual state ; thirdly, that although conception is not 

 confined to the periods of menstruation, yet it is more 

 likely to occur within a few days after the cessation of the 



* See, however, the record of two such cases by Dr. Letheby, in the 

 Philosophical Transactions, 1851. 



