extrusion of ova." Seeing, then, that the ova are discharged at the menstrual periods, and that conception depends on the fertilisation of the ova by the male, it is obvious that conception will most readily take place immediately before or after menstruation. "It is quite certain that there is a greater aptitude for conception immediately before and after that epoch than there is at any intermediate period" (Carpenter). A woman "is more apt to conceive soon after menstruation than at any other time" (Chavasse). So much is this fact recognised by the medical profession, that in cases of sterility a husband is often recommended only to visit his wife immediately after the cessation of the Catamenia. Since women conceive more easily at this period, the avoidance of sexual intercourse during the few days before and after menstruation has been recommended as a preventive check. Dr. Tyler Smith writes: "In the middle of the interval between the periods, there is little chance of impregnation taking place. The same kind of knowledge is of use, by way of caution, to women who menstruate during lactation, in whom there is a great aptitude to conceive; pregnancy, under such circumstances, would be injurious to the health of the fœtus, the child at the breast, and the mother herself, and therefore should be avoided, if possible." The most serious objection to reliance on this check is that it is not certain. M. Raciborski says that only 6 or 7 per cent. of conceptions take place during this interval, but the 6 or 7 exceptions to the general rule prevent recommendation of the check as thoroughly reliable; we can scarcely say more than that women are far less likely to conceive midway between the menstrual periods than either immediately before or after them.
The preventive check which is so generally practised in France that Dr. Drysdale—with a rarely wide French experience—stated that among the peasantry it was "used universally," and was "practised by almost every male in Paris, and all over the country," is one which depends entirely on the self-control of the man. It consists simply in the withdrawal of the husband previous to the emission of the semen, and is, of course, absolutely certain as a preventive. A few among the French doctors contend that the practice is injurious, more especially to the wife; but they have failed, so far as we can judge, in making out their case, for they advance no proofs in support of their theory, while the
