2. In the animal kingdom generally, the reproductive function is _necessarily_ a periodical act, dependent upon the development of the reproductive organs of both the male and the female at stated periods. 3. In those exceptional cases in which the organs of the male are in a state of constant development, sexual congress occurs, in lower animals, only at those periods when the periodical development occurs in the female. 4. Fecundation of the female element can only take place about the time of periodical development in the female. 5. The desire for sexual congress naturally exists in the female only at or immediately after the time of periodical development. 6. The constant development of the sexual organs in human males is a condition common to all animals in which development occurs in the female at short intervals, and is a provision of nature to secure a fruitful union when the female is in readiness, but not an indication for constant or frequent use. 7. The time of sexual congress is always determined by the condition and desires of the female. An additional fact, as stated by physiologists, is that, under normal conditions, the human female experiences sexual desire immediately after menstruation more than at any other time. It has, indeed, been claimed that at this period only does she experience the true sexual instinct unless it is abnormally excited by disease or otherwise. From these facts the following conclusions must evidently be drawn:-- 1. The fact that in all animals but the human species the act can be performed only when reproduction is possible, proves that in the animal kingdom in general the sole object of the function is reproduction. Whether man is an exception, must be determined from other considerations. 2. The fact that the males of other animals besides man in which the sexual organs are in a state of constant development do not exercise those organs except for the purpose of reproduction, is proof of the position that the constant development in man is not a warrant for their constant use. 3. The general law that the reproductive act is performed only when desired by the female, is sufficient ground for supposing that such should be the case with the human species also. The opinions of writers of note are given in the following quotations:-- "The approach of the sexes is, in its purest condition, the result of a natural instinct, the end of which is the reproduction of the species. Still, however, we are far from saying that this ultimate result is, in any proportion of cases, the actual thought in the minds of the parties engaged." "The very lively solicitations which spring from the genital sense, have no other end than to insure the perpetuity of the race."[12] [Footnote 12: Dr. Gardner.]