Many primitive peoples, as well as the theologians of the Middle Ages, have believed that sexual excitement on the woman’s part is necessary to conception, though they have sometimes mixed up that belief with false science and mere superstition.  The belief itself is supported by some of the most cautious and experienced modern gynaecologists.  Thus, Matthews Duncan (in his lectures on Sterility in Women) argued that the absence of sexual desire in women, and the absence of pleasure in the sexual act, are powerful influences making for sterility.  He brought forward a table based on his case-books, showing that of nearly four hundred sterile women, only about one-fourth experienced sexual desire, while less than half experienced pleasure in the sexual act.  In the absence, however, of a corresponding table concerning fertile women, nothing is hereby absolutely proved, and, at most, only a probability established.

Kisch, more recently (in his Sexual Life of Woman), has dealt fully with this question, and reaches the conclusion that it is “extremely probable” that the active erotic participation of the woman in coitus is an important link in the chain of conditions producing conception.  It acts, he remarks, in either or both of two ways, by causing reflex changes in the cervical secretions, and so facilitating the passage of the spermatozoa, and by causing reflex erectile changes in the cervix itself, with slight descent of the uterus, so rendering the entrance of the semen easier.  Kisch refers to the analogous fact that the first occurrence of menstruation is favored by sexual excitement.

Some authorities go so far as to assert that, until voluptuous excitement occurs in women, no impregnation is possible.  This statement seems too extreme.  It is true that the occurrence of impregnation during sleep, or in anaesthesia, cannot be opposed to it, for we know that the unconsciousness of these states by no means prevents the occurrence of complete sexual excitement.  We cannot fail, however, to connect the fact that impregnation frequently fails to occur for months and even years after marriage, with the fact that sexual pleasure in coitus on the wife’s part also frequently fails to occur for a similar period.

“Of all human instincts,” Pinard has said,[422] “that of reproduction is the only one which remains in the primitive condition and has received no education.  We procreate to-day as they procreated in the Stone Age.  The most important act in the life of man, the sublimest of all acts since it is that of his reproduction, man accomplishes to-day with as much carelessness as in the age of the cave-man.”  And though Pinard himself, as the founder of puericulture, has greatly contributed to call attention to the vast destinies that hang on the act of procreation, there still remains a lamentable amount of truth in this statement.  “Future generations,” writes Westermarck in his great history of moral ideas,[423] “will probably with a kind of horror look back at a period when the most important, and in its consequences the most far-reaching, function which has fallen to the lot of man was entirely left to individual caprice and lust.”