IMPREGNATION OF THE OVUM. 899 



that fecundation is effected at the ovary itself. That such occasionally hap- 

 pens in the Human female, seems to be unequivocally proved by the occur- 

 rence of tubal or even of ovarian floatation ; the ovum having received the 

 fertilizing influence immediately 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 impregnation is lost ; but this assertion 

 chiefly rests on the cessation of sexual desire observed in those animals in 

 which, after death, the ova were found in these situations. 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 extru- 

 sion 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 envelopes, and surrounded by the cells of 

 the membraua grauulosa, are received by the fimbriated extremities of the 

 Fallopian 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 the peristaltic movement of their 

 walls, and in part to the action of the cilia which clothe their internal 

 surface. 



748. The object of the changes which have been already described, is to 

 bring the Ovum within the reach of the fecundating influence, and to con- 

 vey it into the uterus after it has been fertilized ; we have now to consider 

 the changes of the Ovum itself, which take place during the same epoch. 

 At about the same period that the ovum moves towards the periphery of the 

 Graafiau follicle, the germinal vesicle moves towards the periphery of the 

 yolk ; 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 zoua pellucida. 

 Thus, the germinal spot is very near the exterior of the ovary; but it is 

 separated from the peritoneal coat of the latter, by a thin layer of its stroma 

 forming the external wall of the Graafian follicle, by the ovisac forming its in- 

 ternal membrane, and by the zoua 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 



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

 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 Jewish females, who abstain 

 from sexual intercourse 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. 14th, 1844.) 



