As heavy gymnastics as the strength of the individual will admit, and plenty of exercise out-of-doors must be taken. There must also be constant mental and physical employment. In women sexual excitability is often caused by local diseases, and passes off with their cure; if not, she must use her will-power, and take the various forms of cold baths. Sexual intercourse not oftener than once in two or three weeks, and avoid all intimate approaches; if this is not sufficient, she will have to leave her husband for a few months. CHAPTER IX. STERILITY. Sterility; the Prevention of Conception and the Limitation of Offspring; the Crime of Abortion; Infidelity in Women. "Never let yourselves do evil that good may come. If you do, you hinder the coming of the real, the perfect good in its due time." -- PHILLIPS BROOKS. Sterility.-- Conception is least apt to take place from the tenth day after one period until the third day before the next; but there is practically no time during a woman's sexual life when she may not be impregnated; in this connection it must be remembered that the spermatozoa stay alive in her for more than a week. During lactation women are generally sterile, especially in the first months which follow the accouchement, because the vital forces are then concentrated on the secretion of milk. The age of the wife at the time of marriage has much to do with the expectation of children. As the age increases over twenty-five years the interval between the marriage and the birth of the first child is lengthened. For it has been ascertained that not only are women most fecund between twenty and twenty-five years, but that they begin their career of child-bearing sooner after marriage than either their younger or older sisters. A wife who has had children and ceases to conceive for three years will probably bear no more. When marriages are fruitless, the wife is almost always blamed; but it is by no means the wife that is always at fault; many husbands are absolutely sterile. Every man is not prolific who enjoys good health and is vigorous. Gross states that in one case out of six the sterility was due to the male. Kehrer, after a series of carefully conducted experiments, has arrived at the conclusion that in at least a third of the cases of sterile marriages the husband was the party at fault, and that gonorrhea was the cause of the barrenness. Venereal diseases have their share of influence, and the gonorrheal infection is a potent cause of sterility. It is by no means proved that syphilis has any unfavorable influence on conception, though abortions due to this are frequent.