1. The greatest number of conceptions follow coitus effected during the first days after the cessation of the menstrual flow.
2. When coitus is effected during menstruation, the probability of conception increases day by day as the end of the flow is approached.
3. The number of conceptions following coitus effected shortly before menstruation is minimal.
4. However, there is no single day either of the menstrual flow or of the intermenstrual interval, on which the possibility of the occurrence of conception can be excluded.
Feokstitow has drawn up from statistical data an ideal “conception-curve,” which teaches that conception most readily ensues upon coitus effected soon after the end of the menstrual flow, in the first week, that is to say, of the intermenstrual interval; moreover, the curve shows that the highest percentage of conceptions occurs on the very first day after the cessation of the flow, and that after this day the percentage of conceptions declines. The percentage frequency of conceptions from coitus effected on the last day of menstruation, and on the first, ninth, eleventh, and twenty-third days, respectively, of the intermenstrual interval, is expressed by the ratio 48 : 62 : 13 : 9 : 1; and between the points given, the course of the curve is almost rectilinear. The probability of the occurrence of conception on the twenty-third day of the interval (on which day the curve reaches its lowest point), is one-sixty-second of the maximum probability.
The proper performance of coitus depends upon the potentia coeundi of the male; the attainment of conception depends upon his potentia generandi. The potentia generandi demands from the man the functional competence of the testicles, the perviousness of the seminal passages (namely, of the vasa deferentia and the urethra), the secretion of a normal semen, and, finally, a proper formation of the penis, whereby during ejaculation the semen may be deposited in sufficient proximity to the os uteri externum.
Normal semen is a whitish, semi-transparent fluid, of the consistency of thin cream. It contains aggregations of a nearly spherical shape, consisting of a vitreous, transparent, colourless or light yellow, gelatinous, elastic substance. Under the microscope this substance has a hyaline appearance, and exhibits in its interior innumerable clear spaces of varying size, which are apparently filled with a clear fluid. Not infrequently, these spaces are extremely narrow and therewith greatly elongated and disposed in parallels, so that the whole substance thus obtains a striated appearance. When treated with water, this material becomes whitish and non-transparent, and assumes under the microscope a finely granular aspect. When allowed to stand without agitation for twenty-four hours, this substance dissolves and becomes so intimately mingled with the seminal fluid that it can no longer be clearly differentiated therefrom. In all probability it is merely a secretory product of the seminal vesicles.
The truly fluid portion of the semen contains the following morphological elements:
1. Microscopic aggregations of hyaline substance, variously shaped.
2. Very numerous granules, small and extremely pale, albuminous in their nature, and disappearing on treatment with acetic acid.