668 



UTERUS AND ITS APPENDAGES. 



sions, which furnish the sole opportunities for 

 impregnation, bear the same constant relation 

 to menstruation that the acts of ovulation and 

 the times of conception in the mammalia bear 

 to the oestrus, it becomes necessary to exa- 

 mine more closely the grounds of this belief; 

 and for this purpose the circumstances as yet 

 ascertained regarding the times of conception 

 in women, the condition of their ovaries, not 

 only during menstruation but in the intervals 

 also, and the actual relation which the oestrus, 

 or period of conception in mammals, bears to 

 menstruation, may be briefly passed in review. 

 The precise period at which conception in 

 the human subject occurs in most cases cannot, 

 for obvious reasons, be determined, but when- 

 ever conception can be traced to a single op- 

 portunity, the process of impregnation, or the 

 fertilisation of the ovum by contact with the 

 spermatozoa, may be assumed to take place 

 within a few hours after the act of insemina- 

 tion ; for the spermatic fluid rapidly traverses 

 the generative canal, while here spermatozoa 

 cease to have motion within thirty hours at 

 latest from the time of emission. 



From various methods of computation it is 

 supposed that in a large majority of cases con- 

 ception occurs during the first half of a men- 

 strual interval, and most commonly during the 

 first week. In sixteen instances noted by 

 Raciborski conception occurred as late as the 

 tenth day after menstruation in only one 

 case.* 



The number of instances in which con- 

 ception can be ascertained, or may be fairly 

 assumed, to have taken place in the latter half 

 of a menstrual interval is comparatively small. 

 Nevertheless impregnation may unquestionably 

 occur during this time, and even within a day 

 or two of the next menstrual flow, which is 

 then usually diminished in duration and quan- 

 tity, or is reduced to a mere show. 



Now if we endeavour to explain these facts, 

 relating to the times of conception, by the aid 

 of an ovular theory of menstruation, the ques- 

 tion may be brought within very narrow limits. 

 One of two postulates may be assumed. An 

 ovum emitted at or soon after a menstrual 

 period either remains susceptible of impreg- 

 nation through the whole of the succeeding 

 interval, or it loses that susceptibility, and 

 perhaps perishes before the recurrence of the 

 next menstrual flow. 



The first hypothesis would sufficiently 

 account for impregnation taking place at any 

 part of a menstrual interval ; but it has little 

 or no evidence for its support. Nothing, in- 

 deed, is known regarding the length of "time 

 during which the human ovum remains sus- 



* These and similar facts have been commonly 

 regarded as showing a greater aptitude for concep- 

 tion shortly after menstruation ; but the influence 

 of mere opportunity has not perhaps been sufficiently 

 considered ; for if, as in the case of the Jews under 

 the strict requirements of the Levitical law, the 

 whole of the first week, or that period which is 

 commonly regarded as most favourable to concep- 

 tion, be withdrawn from the opportunities for im- 

 pregnation, no diminution whatever of prolific power 

 results. 



ceptible of impregnation after it has escaped 

 from the ovary. The period of susceptibility 

 in the mammalia generally is variable. In the 

 bitch, as already stated (p. 606.), the ovum, 

 after quitting the ovary, is supposed to re- 

 main in the tube during six or eight days. Its 

 passage is probably quite completed in ten 

 days. In the guinea-pig the period is much 

 shorter, as the ovum enters the uterus at the 

 end of the third day. In the rabbit also the pe- 

 riod does not extend beyond the beginning of 

 the fourth day. But by the time that the ovum 

 reaches the uterus, or sometimes even the lower 

 end of the oviduct, in most of the mammalia 

 yet observed, the oestrus is past, and with it 

 also the opportunity for impregnation. The 

 evidence therefore obtainable from the mam- 

 malia fails to support the conjecture, that in 

 man an ovum detached during menstruation 

 can remain susceptible of impregnation through 

 the whole of a menstrual interval, consisting 

 of twenty-three or more days, although the 

 period of this susceptibility may be longer in 

 man than in the other examples cited. 



But if this first hypothesis fails, the second 

 appears inevitable, viz., that an ovum emitted 

 during menstruation loses its susceptibility of 

 impregnation before the termination of the 

 succeeding menstrual interval. M. Pouchet 

 supposes, that in the human subject the dura- 

 tion of this susceptibility does not exceed four- 

 teen days. Consequently if, according to the 

 strict formula of the latter physiologist, ova are 

 emitted only at or shortly after the menstrual 

 periods, there must remain a portion of each 

 menstrual interval, during which every woman 

 is physically incapable of conception. And 

 this alternative M. Pouchet* does not hesitate 

 to adopt. 



But since this conclusion is incompatible 

 with the facts already stated regarding the 

 occasional, though probably rare occurrence of 

 conception during the latter portion of a men- 

 strual interval, and especially towards its con- 

 clusion, M. Coste, who shares with many 

 others a belief in these facts, has proposed an 

 explanation which constitutes a very con- 

 siderable modification of the ovular theory of 

 menstruation. To account for impregnation 

 at a later period than usual of a menstrual in- 

 terval, M. Coste supposes that a ripe or dis- 

 tended Graafian follicle, having failed in reach- 

 ing the point of rupture, may remain stationary, 

 as it sometimes does in mammals f, and that 

 the influence of the male is sufficient to de- 

 termine the dehiscence of a follicle in such a 

 state. And in order to anticipate the obvious 

 objection, that if the emission of an ovum from 

 the ovary is the cause or occasion of menstrua- 



* Theorie Positive. M. Pouchet believes that a 

 slender decidua is always formed at the decline of 

 each menstruation, which, together with the ovum, 

 whenever the latter is not impregnated, is cast off 

 from the uterus between the tenth and fourteenth 

 day, and that after this event every woman remains 

 incapable of conception until the" next menstrual 

 period, when the detachment of another ovum from 

 the ovary renews her capacity for impregnation. 



t For a fuller statement of this view, with illus- 

 trative examples, see p. 568. 



