568 GENERATION AND DEVELOPMENT. 



discharge of ova, independently of coition, occurs in Mamma- 

 lia, the periods at which the matured ova are separated from 

 the ovaries and received into the Fallopian tubes being indi- 

 cated in the lower Mammalia, by the phenomena of heat or 

 rut; in the human female by the phenomena of menstruation. 

 Sexual desire manifests itself in the human female to a greater 

 degree at these periods, and in the female of mammiferous 

 animals at no other time. If the union of the sexes take place, 

 the ovum may be fecundated, and if no union occur it perishes. 



That this maturation and discharge occur periodically, and 

 only during the phenomena of heat in the lower Mammalia, 

 is made probable by the facts that, in all instances in which 

 Graafian vesicles have been found presenting the appearance 

 of recent rupture, the animals were at the time, or had recently 

 been, in heat; that on the other hand, there is no authentic 

 and detailed account of 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, ex- 

 cept 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 maturation 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 dis- 

 charged under these circumstances have rarely been discovered 

 in the Fallopian tube, 1 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, independently of sexual inter- 

 course, 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 menstru- 



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

 Philosophical Transactions, 1861. 



