968 OF GENERATION. 



diately upon quitting the ovisac, or even before it has entirely extricated itself 

 from the ovary, and having been in some way checked in its transit towards 

 the uterus, so that its development has taken place in the spot at which it has 

 been arrested. It is affirmed by Bischoff that by the time the ovum reaches the 

 uterus, or even the lower end of the Fallopian tube, its capacity for impregna- 

 tion is lost ; but this assertion chiefly rests on the cessation of sexual desire, 

 observed in those animals in which, after death, it was found that the ova had 

 passed into the uterus, or had arrived at the lower part of the Fallopian tube. 

 There is every reason to believe that this is not the case in the Human female ; 

 for, although the sexual desire may be the strongest about the period of the 

 maturation and escape of the ova, yet it is by no means wanting at other times ; 

 and the occasional occurrence of cases in which impregnation has taken place 

 from a single coitus in the middle of the interval between the menstrual periods, 

 shows either that the ovum may retain its capacity for impregnation for some 

 time after its escape from the ovary, or that its maturation and extrusion are 

 not by any means invariably coincident with the menstrual period. 1 The ova, 

 when set free from the ovaries by the rupture of the ovisacs and the giving way 

 of their several envelops, are received by the fimbriated extremities of the Fal- 

 lopian tubes, which, during the period of sexual excitement, appear to be closely 

 applied to the surface of the ovaries. Their conveyance along the Fallopian 

 tubes is probably due in part to their peristaltic movement, and in part to the 

 action of the cilia which clothe their internal surface. 



973. The object of the changes which have been already described is to bring 

 the Ovum within reach of the fecundating influence, and to convey it into the 

 uterus after it has been fertilized : we have now to consider the changes in the 

 Ovum itself, which take place during the same epoch. At about the same 

 period that the ovum moves towards the periphery of the Graafian follicle, the 

 germinal vesicle moves towards the periphery of the yelk ; and it always takes 

 up its position at the precise point of the zona pellucida which is nearest the 

 ovisac, and which is closest, therefore, to the surface of the ovary. Moreover, 

 the germinal spot is always on that part of the germinal vesicle which is in 

 closest contact with the zona pellucida. Thus, the germinal spot is very near 

 the exterior of the ovary ; but is separated from it by the peritoneal coat of the 

 latter, by a thin layer of its stroma forming the external layer of the Graafian 

 follicle, by the ovisac forming its internal membrane, and by the zona pellucida. 

 As soon as these give way, there is nothing to prevent the spermatozoa from 

 coming into direct contact with the ovum, even before it quits the ovisac. 

 That such contact is an essential condition of fecundation, there is every reason 

 to believe ; although, as to the precise manner in which it operates, we are at 

 present in the dark. There can be no doubt that it is in the contact of the 

 spermatozoa with the ovum, and in the changes which occur as the immediate 

 consequence of that contact, that the act of Fecundation essentially consists. 

 We have already seen that the Spermatozoa constitute the essential part of the 

 Seminal fluid ( 959) ; and although it has been ascertained by Mr. Newport, 

 that the spermatic fluid as secreted by the testes is inferior in fertilizing power 



1 See a case of this kind recorded by Dr. Oldham in the "Medical Gazette," July 13, 

 1849. Instances are certainly not unfrequent in which conception has taken place five or 

 six days after the conclusion of the menstrual period ; the Author has himself known one 

 in which this occurred, after the menstrual flow itself had persisted for a week. It has 

 been urged that the known fertility of the Jewish females, who abstain from sexual inter- 

 course for eight days, or even thirteen days, after the termination of the catamenia, is 

 opposed to the idea that the menstrual period is that of "heat"; but there is reason to 

 believe that this is to be accounted for in another way namely, by the usual occurrence 

 of conception from intercourse immediately before the access of the catamenia. (See Mr. 

 Girdwood, in the "Lancet," Dec. 14, 1844.) 



