determining the existence of such equality, individual characteristics must likewise be taken into account. Whether the crossing of races is desirable is not yet certainly determined.” From the hygienic standpoint it is necessary that in marriage also the frequency and the manner of sexual intercourse should be regulated. Wise men and lawgivers of all the nations of antiquity have insisted upon the necessity of certain intervals between the acts of intercourse. Thus, _Mahomet_ prescribed 8 days, _Zoroaster_ 9 days, _Solon_ 10 days, _Socrates_ also 10 days. _Moses_ forbade intercourse during menstruation and for a week after the cessation of the flow. _Luther_ prescribed intercourse “twice a week.” Birds and many mammals are competent to perform intercourse at exceedingly short intervals. A well-bred cock will repeat this act 50 times daily; a sparrow, 20 times in an hour; a bull, 3 to 4 times in an hour. In the human species, however, too rapid repetition of intercourse is deleterious not only to the male, but to the female also, though the latter certainly suffers in less degree. For in this act the female plays a more passive part, and for this reason can repeat it with impunity more frequently than the male, who loses semen at each repetition. It is not possible, however, to lay down precise rules as to the permissible frequency of intercourse in either sex; the matter must depend upon physical needs. Moderate and regular indulgence in sexual intercourse is unquestionably advantageous to women both physically and mentally, regulating all the functions of the body, and tending to produce a contented and cheerful frame of mind. During menstruation, a woman should refrain from intercourse. By the Mosaic law the death punishment was allotted both to the man and to the woman who indulged in coitus while the latter was menstruating. As a matter of fact, considerations alike of hygienic cleanliness and of sanitary precaution prohibit the performance of coitus during this period. Severe menorrhagia, perimetritic irritation, and parametritic inflammations, have been observed to follow such indiscretions. On the other hand, it is more than doubtful whether, in the event of pregnancy resulting from intercourse performed during menstruation (and conception is especially apt to occur at this time), the child is likely, as earlier authors maintained, to be unfavorably affected, and to suffer from cachexia, scrofula, or rickets. After the act of intercourse, a woman should rest; and indeed sleep for some hours is especially to be recommended. A vaginal douche should not be administered until several hours have elapsed, otherwise there will be a risk of preventing fertilization of the ovum. The water employed for vaginal irrigation should never be quite cold; a temperature of 79°–82° F. (26°–28° C.) is best.