Part 61

But I find in this table, which is based upon a very large number of instances indeed, a confirmation of the thesis which I stated above, for the highest sexual ratio of 113.8 is in this table found in the case of fathers over forty-five years of age who are married to mothers of ages twenty-five to thirty years; this is, as I said, the case in which “the husband is at least ten years older than the wife, and the latter is at the age at which her reproductive capacity is at its maximum.”

From such figures as these, which seem to show the influence of the absolute age of the father upon the determination of sex, it has by many been inferred that the man exercises a preponderating influence upon the determination of the sex of the embryo, impressing his own sex upon it, and that the greater the sexual potency of the begetter the more powerful also is the influence exercised by the latter; that the point of first importance in this connection is the sexual capacity of the man; and that the excess of male births increases pari passu with the increase in the potency of the procreating male.

Two additional considerations have been adduced to demonstrate the influence of the father in determining the sex of the offspring. The first of these is a comparison of the ratio between male and female births in towns and in rural districts, respectively; and the second is a comparison between the ratio of males to females in the offspring of married and of unmarried parents, respectively.

In towns the excess of male births is smaller than it is in the country. The average sexual ratio in Prussia during the five-year period, 1875 to 1880, is given by Düsing as follows:

In Berlin 105.70 In other large towns 105.72 In medium sized towns 105.44 In small towns 106.17 In rural districts 106.62

The indisputable fact that in towns more girls are born than in rural districts is referred to the fact that in the country the husband usually enters on marriage with his virile powers completely unimpaired, whereas in towns many men only marry after they have for many years expended their best forces in irregular sexual intercourse, and thus reserve for their wives only the dregs. But, as we shall show presently, the difference between town and country in this respect is susceptible of a different interpretation.

It has also been asserted (Horn) that extra-conjugal sexual intercourse is favourable to the procreation of boys, the suggestion being that the greater sexual vigour in the former case determines a preponderance of males in the offspring; but this assumption is invalidated by the statistical evidence which now accumulates, that among illegitimate offspring there is a smaller excess of boys than among legitimate offspring. Babbage, for instance, came to this conclusion as a result of the comparison of 1,000,000 illegitimate births with 14,000,000 legitimate births. On the other hand, the following utterance of Ploss appears extremely artificial: “In a country in which illegitimate births are very numerous, in which the illegitimate children are for the most part begotten by enervated debauchees, the excess of male births is smaller; but in a country in which the illegitimate births are less numerous, and in which the illegitimate infants are for the most part the fruit of love and are begotten by youthful lovers, the excess of male offspring is larger.”

Next to the age of the progenitors, their nutritive condition is shown by statistical investigations to exercise an important influence in the determination of sex. The following proposition has, in fact, been established: Where the supply of nutriment is deficient, the offspring contains an excessive proportion of boys.

Ploss, in an article on “The Causes of Variations in the Sexual Ratio,” published in twelfth volume of the “Berliner geburtsh. Monatsheft,” has collected a number of statistical data to demonstrate that the determination of sex is principally dependent upon the nutritive condition of the mother. In his opinion the determination of the sex of the embryo depends neither upon the quality of the ovum nor upon that of the spermatozoon, nor again upon the reciprocal influences exerted by ovum and spermatozoon on one another. During the earliest time after fertilization the embryo is sexually neutral and only later, as a result of some new influence acting upon it, does it receive an impulse toward the formation either of the male or of the female sex. Among all the external conditions which are capable during this period of exercising a determinative influence the most important are the nutritive conditions, for nutrition is the most important factor in determining the form of the young animal, and most of the other outward conditions, such as light, heat, and chemical changes, affect the embryo in a mediate manner only, through the changes they are respectively capable of inducing in its nutrition and metabolism. But Ploss is not content with asserting that the nutritive condition of the mother is of great importance in determining the sex of the embryo; he goes further than this, and declares that it is scanty nutrition of the mother which especially gives rise to the birth of males, whereas abundant nutrition of the mother tends to give rise to the birth of females. He refers to observations made in respect of other animals than man. St. Hilaire observed that among the underfed animals in menageries there was an excess of male births. Hofacker and Girou de Bazarcingues have noted similar phenomena in the case of domestic animals; they found that when these were richly fed they gave birth to an excess of females, but that when they were poorly nourished they gave birth, on the contrary, to an excess of males. Among sheep, with whom the number of male and of female births is approximately identical, Martegoute found that those animals which had given birth to female lambs had on the average a greater weight than those ewes which had given birth to male lambs. During the period of lactation, also, the former lost weight more than the latter.

When Ploss had further ascertained that among those engaged in the fur-trade it is the established belief that from fruitful regions the skins chiefly of female animals will be obtained, but from barren regions, on the other hand, among the skins obtained those of male animals will preponderate, it appeared to him that he was justified in drawing the conclusion that among the mammalia a well-nourished mother, one capable of providing abundant nutriment for her offspring, is, on the whole, more likely to give birth to a female than to a male, and conversely. He then endeavoured, by reference to the statistics of population, to show that in the case of human beings also, when the mother is exceptionally well nourished, there is especial likelihood of a girl being born; whereas when the mother is ill nourished she is more likely to give birth to a boy—odd as it may seem, at first sight, that a rich diet should determine the production of the so-called less powerful sex, the female; and conversely. (Ploss, be it noted however, denies that male new-born infants are more powerful than female.) The fact that in the country, comparatively speaking, many more boys are born than in towns (vide supra) is explained by Ploss as dependent on the fact that townswomen are on the whole better nourished than the countrywomen, owing to the greater consumption of meat by the former.

The circumstance again (likewise alluded to above), that in the case of illegitimate births almost always the excess of male births is less marked than in the case of the offspring of legal unions, is regarded by Ploss as offering further proof of the influence of nutritive conditions upon the determination of sex. Illegitimate mothers are on the average women at the very best age for child-bearing, women who have worked vigorously, are themselves well nourished, and are therefore better able to nourish their unborn offspring than (on the average) married women. Further, it is a remarkable fact that in Saxony, regions of which the elevation above the sea-level is less than 1,000 feet, produce comparatively more girls than regions at an altitude of 1,000 to 2,000 feet above the sea. This Ploss refers to the worse nutrition of the women living at the higher altitude, for the fact is well known that the higher we go above the sea the less fertile is the soil and the more limited is its produce.

Starting from the view that the lower classes of the population are in good years better nourished than they are in bad years, Ploss compared statistically the rise and fall of the prices of foodstuffs, in Saxony, with the variations of the sexual ratio in the same kingdom; and he found, in correspondence with his theory, that in bad times there was a greater excess of male births than there was during periods in which food was cheaper. Moreover, the consumption of meat appeared to have more influence upon the variations in the sexual ratio than was exercised by the consumption of vegetable foodstuffs. Ploss endeavoured to show graphically that with an increase in the price of provisions there corresponded an increase in the excess of male births, and vice versa.

That after times of great wars, pestilence, and emigration, in which the male portion of the population has been decimated, there occurs a notable increase in the excess of male births, is explained by Ploss by the assumption that in consequence of the deficiency of male labour, the general supply of provisions is deficient, just as it is after years of bad harvests; hence, in consequence of the scanty nutrition of the mothers, the number of female births is depressed and the number of male births increases. Those countries which in general possess a more thriving population, such as Saxony, England, Belgium, Prussia, etc., exhibit a smaller excess of male births when compared with those countries in which a more widespread poverty exists, such as Russia, Lombardy, Bohemia, and even France. With increasing prosperity, fruitfulness increases, and there is an increase also in the proportion of female births.

These views of Ploss’s are, however, rightly contested by Breslau and Wappaeus.

Breslau (“The Causes of the Determination of Sex”) offers in the first place theoretical objections to the view that nutritive conditions in the mother are determinative in the production of the sex of the offspring; and he then proceeds to quote statistical data which are opposed to any such theory. He rightly insists, in the first place, that, inasmuch as it is unquestionable that in the act of fertilization the spermatozoon induces in the ovum certain changes, the effect of which is manifested in days far later than those of intra-uterine life, by the production of the most manifold and various somatic and psychical resemblances to the father, it is obvious that this single occurrence of the fusion of the spermatozoon, the bearer of the paternal influences, with the ovum is competent to induce in the ovum a molecular arrangement upon which the determination of sex may be supposed to depend—it is not necessary to suppose that for this determination, repeated actions, or a prolonged period of time, is requisite.

In this connection a reference to birds is instructive, for in this division of the animal kingdom we seem absolutely compelled to assume that the sex of the offspring is irrevocably determined in the moment of fertilization. “In birds, who lay an egg every day, eggs which are kept all at the same temperature during the period of incubation, and some of which develop into cock and others into hen birds—how is it possible to imagine that the nutritive condition of the parent is determinative of the sex of the offspring, since this nutritive condition cannot reasonably be supposed to change to any notable extent from one day to the next and then back again?”

The paternal influence in the determination of sex is regarded by Breslau as likely to be at least as important as that exercised by the mother. Unquestionably the semen is subject to certain variations in quality and in quantity, and it is possible that these variations may make themselves felt in the subsequent development of the embryo. Of the semen, as of all secretions, we can assume with some probability that in certain conditions (conditions which are, indeed, but little understood), it may exhibit a greater or less intensity in its stimulating qualities, and that in this way it may be subject to changes, according to which it will tend to influence the development of the embryo, now in the female, and now in the male direction. Again, in view of the continued interchange of nutritive materials between the embryo and the maternal organism, it is probable enough that the constitution of the maternal organism and likewise that of the ovum, at the moment of fertilization, are not matters of indifference to the determination of sex. But to attribute to the nutritive condition of the maternal organism the sole or even the principal influence in the determination of the sex is an unjustifiable assumption.

The proofs alleged by Ploss from the animal world in support of his thesis, viz., that in the case of poorly nourished animals there is a marked excess of male offspring, are justly controverted by Breslau with the remark that the observations on animals are but few in number, and further that we know nothing whatever regarding the normal sexual ratios among the offspring of such animals as lions, tigers, hyænas, bears, etc., in the free state.

If, again, domestic animals when well nourished give birth to an excess of female offspring, and when ill nourished and overworked to an excess of male offspring, in the former case we can only regard the excess of female births as a pathological phenomenon, inasmuch as a superabundant supply of nutriment is not that which furnishes the highest powers or is most suited to the preservation of life. Again, the accounts given by fur-dealers are quite untrustworthy, since these men commonly obtain their goods at third and fourth hand; moreover, most of the animals whose pelts form articles of commerce, are beasts of prey, such as the otter, the lynx, the bear, the wolf, the fox, etc.—and these animals have no “pasturage.” Among vegetable-feeding animals the females are no doubt found on the pasturage more often than the males, for the reason that the females have to nourish both themselves and their young, whereas the males, which have themselves only to provide for, are contented with less food and inhabit chiefly more retired and less fertile regions; they are also shyer and are less easily shot and trapped. Regarding statistical data relating to the influence of nutrition on the production of boys, Breslau shows, from the figures of the Canton of Zurich, that with few exceptions, the years in which the price of corn was lowest were the years in which the production of boys was greatest, and vice versa—the exact opposite of the results obtained by Ploss from his examination of the figures relating to births and the price of provisions in Saxony.

Wappaeus contests the conclusions of Ploss even more vigorously, and adduces the statistics of Sweden in the 20–year period 1770 to 1790, in which period this kingdom repeatedly suffered from famine in consequence of failure of the crops, so that the births and deaths were largely affected. It appeared, however, that the more abundant or more scanty nutrition of the inhabitants of Sweden during this period had no marked influence upon the sexual ratio.

If scanty nutrition of the mother had, in fact, any influence upon the determination of the sex of the embryo in the direction alleged by Ploss, viz., so as to bring about the birth of a greater excess of boys, this influence should be manifested with exceptional clearness in the case of twins, for it is obvious that the nutriment that is insufficient for one embryo would be still scantier for two. Hence various statistical investigations have been undertaken to determine the sexual ratio in the case of twin births. Ploss found that in Saxony, in the case of 23,420 twin births, the sexual ratio was 106.7 boys to 100 girls; Moser gives the sexual ratio in the case of twin births as 106; Meckel von Hemsbach gives it as 105.4; Hecker, 116 and 122; Sickel, 112.3. Düsing combined the figures relating to twin births in various lying-in hospitals, published by Hecker, Sickel, Baillarger, Siebold, Elsässer, and Levy, respectively, and thus obtained a sexual ratio of 121.5 boys to 100 girls. This excess of boys is notably greater than among births in general.

But other statistical data are available which show a reversed condition, viz., that in the case of twin births the sexual ratio is lower than usual. According to von Frick’s collection of twin births in Prussia, the sexual ratio was 104.7 boys to 100 girls; whereas in the case of single births in the same country the sexual ratio was 106.35 to 100. Riecke, in Württemberg, in the case of 60 twin births found 58 boys and 62 girls. In the case of twin births observed by Braun, Chiari, and Späth, 94 in all, the children were in 64 of these of identical sexes, namely, in 30 instances boys, and in 34 instances girls. According to Breslau, in the case of twin births in the Canton Zurich, the sexual ratio was 104.1 to 100; whereas in the case of single births the sexual ratio was 106.2 to 100.

As regards triplets the reports of the sexual ratio vary from 111.76 : 100 (Meckel von Hemsbach) to 104.55 : 100 (Neefe).

It is obvious that the statistical data at present available regarding the sexual ratio in the case of multiple births are far too variable for it to be possible to base upon them any valid conclusions as to the influence of the nutritive condition of the mother upon the determination of the sex of the offspring. And taken as a whole the statistical data hitherto available do not enable us to infer with confidence that nutritive conditions, and more especially the nutritive state of the maternal organism, exercise any effect upon the determination of the sex of the offspring.

Another attempt at the utilization of statistics has been to ascertain whether the time of fertilization in relation to menstruation, (in the first days after the flow, or later in the intermenstrual interval) has any influence upon the determination of sex. The starting point in this investigation was the earlier view that sex depends upon the state of the ovum, and the belief that a very favourable state of ovum and sperm favours the production of the female sex. The ovum, after its discharge from the ovary, like the spermatozoon after its discharge from the testicle, tends sooner or later toward death, and the only thing that can save either from this ultimate fate, is for the two to unite to form a new organism. Precisely what moment in the history of the detached ovum is the most favourable, is a matter regarding which we have no exact information, but it is probable that at the moment of its discharge from the ruptured follicle, it is at the zenith of its vital powers. On this theory the determination of sex depends upon the period at which, after its liberation from the follicle, the ovum encounters a spermatozoon; the ovum which is fertilized early in its career becomes a female embryo; the ovum, on the other hand, which is not fertilized until it has become comparatively old, becomes a male embryo. But, as Hensen points out, a spermatozoon, according to its condition, may either fail sufficiently to fortify an ovum which itself is in good condition; or, on the other hand, a powerful spermatozoon may fortify an ovum of deficient vitality. But it is difficult to say precisely on what considerations the greater or less vitality of the spermatozoon depends—or, to speak more in accordance with the terms of the theory, we do not know exactly what makes it a good spermatozoon or the reverse. It may be “bad,” either because it has remained too long in the testicle or because it has been discharged too quickly, is too recently secreted; moreover, a long sojourn of the spermatozoon in the uterus will doubtless suffice to lower its vitality.

The Jews, more especially, whose religious ordinances forbid them to have sexual intercourse either during or shortly after menstruation, and among whom there is a great excess of male births, have been adduced as a proof of the thesis that sexual intercourse during the later part of the intermenstrual interval tends to favour the procreation of boys. In Leviticus xv. 19, we read: “And if a woman have an issue, and her issue in her flesh be blood, she shall be put apart seven days.” From the commentary in the Talmud it appears that these seven days are to be reckoned from the commencement of the flow. Statistical reports from various countries show that among the Jews there is a greater excess of male births than among the other inhabitants of the respective countries. The overplus of male births exhibited by the Jews varies from 1 to 15%, the difference probably depending on the fact that the number of instances under consideration is too small for uniform results to be possible. In Prussia, during the period 1820 to 1834, the sexual ratio among the Jewish births was 111 : 100; during the period 1849 to 1852 it was 106 : 100; in Hungary during the period 1835 to 1855 it was 117.1 : 100; in Sweden, 1851 to 1855, it was 108 : 100. Among illegitimate children of the Jewish community the sexual ratio was, in Austria, 123.9, in Prussia, 118.6.

Fürst, examining the cases in von Braun’s clinic, and making a statistical collection of the days of conception and of delivery, has endeavoured to prove that “there is an excess of boys when conception occurs during the period of post-menstrual anæmia.” His figures show, in fact, a very notable excess of boys in cases in which conception has occurred during the five days immediately following the cessation the menstrual flow; and an excess of girls when conception has occurred during the later part of the intermenstrual interval. Thus, in the former case the excess of boys is represented by the figures 37 : 12; in the latter case the excess of girls is represented by the figures 79 (girls) : 65 (boys). These figures are explained by Fürst on the theory that in the human species conception during the period of post-menstrual anæmia probably leads to an enormous excess of male conceptions (owing to the fact that the unfertilized ovum is badly nourished during the days just before conception); whereas in the later part of the intermenstrual interval the better nourishment of the ovum probably leads to the procreation of an excess of girls—hypotheses which are based on a quite inadequate number of instances. Fürst gives the following table:

═════════════════╤═════════════════╤═════════════════╤═════════════════ NUMBER OF DAYS │ Number of boys │ Number of girls │ Boys and girls BETWEEN REPUTED │ born. │ born. │ together. END OF │ │ │ MENSTRUATION AND │ │ │ REPUTED │ │ │ OCCURRENCE OF │ │ │ CONCEPTION. │ │ │ ─────────────────┼─────────────────┼─────────────────┼───────────────── 1│ 7│ 1│ 8 2│ 6│ 3│ 9 3│ 9│ 5│ 14 4│ 15│ 3│ 18 5│ 3│ 6│ 9 6│ 5│ 6│ 11 7│ 6│ 5│ 11 8│ 2│ 8│ 10 9│ 4│ 5│ 9 10│ 6│ 4│ 10 11│ 6│ 5│ 11 12│ 3│ 6│ 9 13│ 4│ 5│ 9 14│ 6│ 5│ 13 15│ 1│ 2│ 3 16│ 2│ 5│ 7 17│ 2│ 3│ 5 18│ 3│ │ 3 19│ 1│ 3│ 4 20│ 1│ 2│ 2 21│ 1│ 1│ 2 22│ 4│ 1│ 5 23│ │ 1│ 1 24│ 1│ │ 1 25│ │ 2│ 2 26│ 2│ │ 2 27│ │ 1│ 1 28│ 1│ 1│ 2 31│ 1│ │ 1 ─────────────────┼─────────────────┼─────────────────┼───────────────── │ 102│ 91│ 193 ═════════════════╧═════════════════╧═════════════════╧═════════════════