While many ingenious theories have been advanced in recent years touching the precise point, or period, at which impregnation takes place, it is regrettable that at the present stage of the investigations no authoritative judgment, founded on actual knowledge, can be passed. From observations, however, made in a great number of cases by Tait, Kruger, Pozzi, Schroeder and others, it is apparently certain that it must occur, as to time, during the first half of the menstrual period, and most probably within a week after the cessation of the catamenial flow. RaciboBki observed sixteen eases in which conception occurred as late as the tenth day after; and from what I have been enabled to glean from a vast mass of literature on the subject, it is fair to assume that fully ninety-nine percent, of all cases occur within twelve days after termination of the monthly flow.
There is little substantial evidence to support the theory that impregnation may occur at any time by the mere rupture of an ovisac; nor is it at all probable that the ovum may be retained in the Fallopian tube from one menstrual period to another; the contrary, indeed, being pretty hilly established by examination of animals.
The most probable hypothesis is that the ovum, after ejection from the ovary, is from six to twelve days in passing through the tube, and that impregnation occurs within that place and period. Pouchet extends the time to fourteen days, as does also M. Coste; but the slight difference in time is of little consequence, the important feature of the discussion being to fix the place and method in which, and by which, impregnation takes place.
This has apparently been done; at least with such a degree of certainty as to justify us in believing that whenever a conception takes place after the twelfth or fourteenth day of the menstrual interval, it is owing to the Graafian vesicle having failed to discharge the ripened ovum, the one which came to maturity at the previous menstrual period; which ovum being ruptured by the excitement of sexual intercourse, at any time prior to the next subsequent menstruation, may insure impregnation.
The summary of our established facts, then, seems to be, that it is during the menstrual period that the female ova are ripened. That from the ovary they are discharged into the Fallopian tube, the journey through which occupies them from six to fourteen days, according to functional activity, and that, if impregnation occur at all, it must occur before the ovum has passed out of the tube. Should it not be fertilized by the male spermatozoon uritkin the tube, or within the ovary itself, there will be no impregnation, the ovum passing into, and being lost in, the womb.
Then, if five days be allowed for menstruation, and fourteen for the passage of the ovum through the tube, there remains—and this is the point arrived at by the previous remarks—a period of nine days during which impregnation cannot occur.
I use the word cannot, of course, only as a substitute for "extreme improbability;" the ratio in which it may occur—once in every three to five hundred cases—being such as to practically exclude it from consideration. The question then arises—knowing what we do concerning the phenomenon of fecundation, only a bare outline of which is here given, are there circumstances, physical, mental, moral, social or domestic, which would justify us in preventing it? For, that it can be prevented, notwithstanding all that has been written to prove the reverse, scarcely admits of a doubt.