Part 45

FIG. 55A.—First Stage. FIG. 55B.—Second Stage.

Entrance of a spermatozoon into the ovum of ascaris megalocephala. After preparations by M. Nussbaum. (Half of the ova only are depicted.) ]

FIG. 56.—Ovum of Asterakanthion ten minutes after fertilization. ]

FIG. 57.—Fusion of male pro-nucleus and female pro-nucleus to form the segmentation nucleus of the fertilized ovum. ]

The most favourable period for the occurrence of fertilization appears to be when intercourse takes places from eight to ten days after the termination of the menstrual flow. In 248 instances in which the date of the fruitful coitus was exactly known, it was ascertained by Hasler that in 82½ per cent. of all cases, conception was effected in the fourteen days succeeding the menstrual period. In general it may be stated that the theory of the periodicity of ovulation and of the causal relation of this process to menstruation, has not been shaken by the result of researches recently undertaken by opponents of that theory; hence it appears that the fertilized ovum is the ovum of the last completed menstruation.

Already in the writings of the old Indian physician Susruta, we find expression of the view that the period that immediately succeeds the cessation of the menstrual flow is one most favourable to conception. “The time of generation,” he says, “is the twelfth night after the commencement of menstruation.” In the Jewish Talmud, the day before the onset of menstruation, and the days immediately succeeding the cessation of the flow, are indicated as those most favourable to the occurrence of conception; moreover, in the Talmud, notwithstanding the fact that intercourse during menstruation is prohibited on pain of death, and that coitus is not regarded as permissible until the lapse of twelve clear days after the cessation of the flow, nevertheless the assertion is made that intercourse during menstruation may lead to conception.

FIG. 58. —Passage of spermatozoon through the zona pellucida of the ovum of asterakanthion. ]

FIG. 59.—Ovum of scorpæna scrofa thirty-five minutes after fertilization. ]

FIG. 60.—Male pro-nucleus and female pro-nucleus in fertilized ovum of frog, prior to the formation of the segmentation nucleus. ]

Hippocrates writes: Hae nempe post menstruam purgationem utero concipat. Aristotle says: Plerasque post mensum fluxum nonnullas vero fluentibus adhuc menstruis. Galen writes: Hoc autem conceptionis tempus est vel incipientibus vel cessantibus menstruis.

Soranus writes to a similar effect: Just as the soil is suitable only at certain seasons for the reception of the seed, so also in the human race intercourse does not always take place at a time suited for the reception of the semen. To be effective, coitus must occur at the proper time.... The act of intercourse that is to lead to conception may best occur either just before or just after the menstrual flow, when, moreover, there is strong desire for the sexual embrace, and neither when the body is fasting, nor when it is full of drink and undigested food. The time before menstruation is, however, unsuitable, for then the womb is heavy from the flow of blood, and two conflicting tendencies will come into operation, one for the absorption of material and the other for its outflow. During menstruation, again, conception is unlikely to occur, for then the semen is wetted and washed away by the flowing blood. The sole proper time is that immediately after the flow, when the womb has freed itself from its humours, and warmth and moisture stand in harmonious relationship.

Among many of the castes of Hindustan, it is a religious ordinance that on the fourth day of menstruation a man shall have intercourse with his wife, “since this day is that on which conception is most likely to occur.” Indian physicians advise, in order to bring about conception, “that coitus be effected always as soon as the menstrual flow has ceased, at the end of the day, and when the lotus has closed.” In Japan, medical opinion is to the effect that a woman is capable of conceiving during the first ten days after menstruation, but not later (Ploss and Bartels).

The view that the first days of the intermenstrual interval are those most favourable to the occurrence of conception, is further confirmed by the statistical data collected by Löwenfeld, Ahlfeld, Hecker, and Veit; and it appears that as the date of the next menstruation is approached, there is a continual decline in the frequency of conception; just before the flow, conception hardly ever occurs. Hensen, from the records of 248 conceptions in which the date of the fruitful intercourse was exactly known, draws the following conclusions:

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.

3. A small number of rounded or oval cells, about the size of leucocytes, containing one, or sometimes two small round nuclei.

4. Prostatic calculi. These are an inconstant constituent, but are very frequently met with after repeated coitus. According to some observers they are derived also from the bladder and urethra. They are distinguished by their yellowish colour, their irregular form (sometimes triangular, sometimes rounded or oval), and by their characteristic structure. They are composed of a substance arranged in concentric laminæ, which in the centre has a granulated appearance; they often exhibit one or more oval nuclei.

5. Spermatozoa in countless numbers.

In exceptional cases we find as additional morphological elements, especially in elderly people, scattered erythrocytes, cylinder-epithelium cells, and masses or granules of yellow pigment.

The spermatozoa are about fifty micromillimetres in length. Two parts may be distinguished in each, a head and a tail. The head, four or five micromillimetres in length, is flattened, and differs in apparent shape—though generally more or less pear-shaped—according as to whether it is seen sideways or on the flat.