STERILITY IN GENERAL.
There is no small difference between the animal and human species in the promptness with which conception is caused by co habitation. If we only congider here the more highly organized animals, we find that usually one cohabitation, at least at the time of the sexual excitement, the rut, is sufficient to cause impregnation. This is not the ease usually in the human species, and this fact exerts a considerable influ ence upon its fruitfulness. If the usual belief that the sexual capabilities in women last as long as menstruation occurs, in other words, about thirty years, is correct, and if we accept eighteen months as the average duration of pregnancy, puerperium and Is..ctation, then the number of a woman's parturitions is disproportionately small. In England, the average num ber of children to each marriage is 5.2; in Austria only 4. Certainly the sexual relations in the human species are different than in animals. Above all things, in the human species the first coition does not corre spond with the appearance of puberty, but occurs later; further the marital procreation is very often terminated a long time before the climacteric period, by the death of the husband or by some other separation of the married parties. Among the marriages used for statistical purposes, many are included which have been terminated by the early death of the wife. Those frequent interruptions of pregnancy in the human species, which do not diminish the number of conceptions, but influence the number of normal parturitions, must also be taken into consideration in the estimation of the fertility of the married parties. Aside from the very weighty condition that civilization has many reasons for artificially checking married fruitfulness, there are remaining those numerous dis turbances of health and those social relations in the human species which are so unfavorable to fruitfulness. But in spite of all these, the fruitfulness of the human species is, under altogether normal conditions and with the same or nearly the same duration of pregnancy, greatly less than that of animals. This is very plainly shown by the statistics, compiled in England, of eighty mothers of the poorer classes, who had married between the ages of fifteen and nineteen years, and whose marriage had lasted at least thirty-one years, and therefore during the whole period of fecundity. These fruitful wives had only
averaged a little oyer nine children each. The number would certainly be much larger if the sexual intercourse was followed by immediate result. And though we do not accept the calculations just given as positive proof, since we may have doubts, and as I believe, rigliVully, whether the period of sexual capability and menstruation are the same, we cannot so easily dispute the following argument. The frequent un fruitfulness of cohabitations, when we consider how extremery seldom immediately after marriage, where certainly the influence of artificial hindrances to conception may be almost entirely excluded, impregnation occurs, and the great number of menstrual epochs necessary for procrea tion, are most striking. According to Puesch, in five only of ten fruit ful marriages did parturition occur before the end of the first year; in four at the end of the second year, and in one only at the end of the third year. According to Spencer Wells, ill only four out of seven marriages did delivery occur inside of eighteen months. This proportion is more marked in a calculation of M. Duncan, based upon a larger number of cases. In only about one-sixth of all the cases did parturition occur before the lapse of the first year after marriage; in a little less than four sixths in the second year of marriage. This view is approached by Sad ler, who noticed that in about three-fourths of all the cases observed by him, parturition occurred one year after marriage. According to Ansell the proportions are more favorable. but even according to him, parturi tion in half the cases first occurs after the first year of marriage. He calculates the time between marriage and parturition to be sixteen months. All of these results correspond exactly with those experiences which can be derived from ordinary life. The immediate occurrence of conception then seems to be the rule among animals, the exception among the human species. This difference may have its foundation in the cumulation of different causes, although the attention, in more thorough investigations, is always directed to certain deviations in the structure and function of the genitals.