The facts observed and recorded by others assisted me to advance so far on the trodden path that I made an effort to snatch a secret from Nature.
What I succeeded in obtaining, though small, induced me to set forth in the following pages the perhaps not unimportant results.
The labor was long, and engaged my attention for years. And yet, amidst my continuous labors in the province of Embryology, it remained all the time a matter of secondary importance, my principal attention being engaged by far more extensive studies.
My desire is to stimulate others to wider observation. May the facts which I here discuss prove of utility, and encourage further studies in this direction with the assistance of modern science.
If we are not in a position to control the processes of Nature, we can nevertheless exercise over them a more or less effective influence, so as to obtain such results as are possible.
Whatsoever the question may be that we propose to discuss, it is sometimes very difficult to reach any answer. And yet, when experience and diligence have helped us over the difficulties, we succeed at last in reaching the answer desired. The difficulties assume much less formidable shapes when an individual is satisfied with shaking his head and regarding the whole affair with mistrust. In that way the inexperienced and lazy are at once able to launch their views without further trouble. They believe or they disbelieve; and they like to have their say. Any one can in this way easily win himself a place amongst those who have written on a topic. The man who desires to obtain a lasting place takes on his shoulders heavier responsibilities.
This book contains but a portion of the vast and wide-reaching literature dealing with the subject in hand. That literature extends back to the date of man’s earliest intellectual labors. The observations that have been recorded by others are here followed by methods of investigation, and by considerations which may serve to elucidate the facts. In conclusion, a section has been dedicated to the methods which I recommend for the artificial influencing of sex. Some particular experiments are subjoined.
May my little book, then, go out into the world and make known my views, which are founded exclusively upon facts.
In sexually differentiated individuals, the difference of sex is already apparent in the embryonal state of existence, not only in the exterior form, but also in the interior cellular rudiments which subsequently form the genital organs. In both, the earliest forms are of such a nature that, up to a certain period, it is impossible for investigations conducted with the means at present at our disposal to discover any distinction. Soon, however, after this, in such organisms as have a distinction of sex, elementary male and female forms of the organs of reproduction can be recognized developing themselves in the embryo out of the substratum of formative elements. Some of these remain in a rudimentary condition; others attain to complete development.
These processes take place at a relatively early period. They do not seem to make their first appearance, as phenomena of vitality, in the course of the life-development of the cells of the ovum. But it is not improbable that, from the very outset, the ovule has a capacity to transfer (during the process of segmentation) to a corresponding cell-substance (out of which the generative organs will be subsequently developed) the force contained in the ovule, so that the cell-substance may afterwards take up the office of providing for the preservation of the species. The cells of the ovum derive this power from the protoplasma of the ovum, and retain it in a rudimentary form for one sex, whilst for the other they possess it in full measure. This energy is contained in the ovule itself in an unknown condition. In it lies the basis of the formation and development of the future sex. In close connection with this property of the ovule, lies another faculty, included in the ovule, namely, that the other different elements proceeding from the cell-body of the ovum, starting from the protoplasma of the ovum, are endowed with certain vital peculiarities, according as they belong to the future male, or female, organisms.
It will be plain from this that the germ of the future sex must be sought in the first cell-segmentation of an ovum. As soon as some of the cells derived from the primary protoplasm of the ovum have developed themselves into genital cells, the other elements which have originated from the same ovum are in such a manner conditioned that, in the latter stages of their vitality, they adapt themselves, and, in short, adapt the properties inherent in all the cells, to the sex of the individual. According, as the ovum is male or female, so are also the cells which originate from it either all male or all female.
It will be seen that not only do different cells for the different sexes develop themselves out of an ovum, but that also, at the same time with these, a peculiarity reveals itself in the other cells, in accordance with which the sexually different organisms exhibit a difference in their vital capacities, and take also different forms. The distinction between male and female characteristics appears to be determined before the fecundation of the ovum. The formation of the ova in the ovary, and their further development, seem, however, not to be independent of external influences. It is possible that upon these circumstances depend the number of ova contained in the ovary. But, apart from the question of quantity, it is possible that many characteristics might so affect the quality of the ovum, as to exercise an influence over its capacity for fecundation. We may here mention an experiment which was made with the ova of a rabbit, from which it was quite clear that the capacity of an ovum for fecundation was immediately diminished when the surrounding elements attached to the ovule, in consequence of the density of their investing substance, offered a resistance to penetration by the spermatozoa. (Schenk.) The penetration of a spermatozoon into the protoplasm of the ovum becomes possible only when, in consequence of the movements of the spermatozoon, the cells of the surface of the ovum can be thrust aside. This is facilitated when the investing substance is considerably relaxed, as is the case when the ovum is ripe. Other circumstances, also, which can in some cases be easily detected, may prove detrimental to fecundation and development. Indeed, they can even exercise an influence over the sex which is to be developed out of the ovum. Bee-masters (F. Gerstung) have frequently shown that the food exercises a striking influence upon the formation of sex in the ova. (v. Berlepsch.)
All evidence goes to support the view that such external influences as would favorably affect the separate sexual individual might also promote the production of one sex or the other. In Hensen’s valuable work on generation, a number of instances are adduced, gathered from various authors, which make it clear that the nutrition of the parents, apart from any question of race, is capable of exercising an influence upon the sex of the children. (Ploss.) In plants which produce separate male and female blossoms (Lenkhart), the male blossoms are more numerous when the temperature is relatively high, whilst in shaded places and damp soils a greater number of female individuals will be observed.
Facts which might assist to explain the origin of sex have been sought after from very early times, and have been also placed in very different lights. The result on every occasion, when this subject has been discussed, has been always a wide difference of opinion. People have, in consequence, been induced to fall back upon theories of different sorts, theories which have for varying periods, sometimes long, sometimes short, been accepted as of some assistance towards a scientific explanation. In all the theories which have been propounded, the sex has been regarded as already determined in the ovum, or else the origin of the sex has been assigned to some early stage of the development.
The earliest statements extend back into the ages of myth and fable, in consequence of which any exact comparison of them is not an easy task. All the different manuals which deal with the present question touch upon these early views, and for this reason I am unwilling entirely to ignore them here. I shall, accordingly, select a few of the more important for mention.
The reproductive glands of the two sexes were supposed to contain generative matter distributed in such a way, on the right and left, that the right ovary and the right testicle contained the generative secretions for the production of the males, and the left ovary and left testicle those which produced females. It is immediately evident that, according to this theory, it was impossible to exercise any influence over the sex of the future individual. This primitive theory is ever cropping up anew, always to be again rejected. Of various other theories of the same kind, only those deserve any attention which rest upon some basis of fact. Accordingly, recourse has been had to statistics, and an attempt has been made to reach, from the figures which they furnish, some certainty respecting which sex was the more numerous, and what should be concluded to be the cause of the greater prevalence of the one sex or the other. The fact was, however, apparently overlooked that the available statistics, though in many respects of the highest scientific value, could be of real significance only when the numbers were gathered from widely distributed peoples amongst whom there was none of that wandering about the world which characterizes modern society.
I am at the same time unwilling to omit data, resting upon numbers which have been gathered from statistics, and are not without value for the determination of many important questions.
Ploss has in this way shown that in favorable years, when food was cheap, the births showed an excess of girls. Under unfavorable circumstances, more male individuals were born.
A comparison of statistics, however, soon led to another theory, which culminated in this result, that in all countries an excess of male individuals was born.
To what extent this relation between the numbers of the sexes can be maintained, and may serve for a fixed rule, is at the same time a question to be regarded with caution. An unimpeachable result of such investigations is rendered more unlikely by the fact that comparisons of numbers lead to a conclusion of an exactly contrary nature, making the feminine sex the more numerous. These facts at once suggest that we are not dealing with fixed or normally recurring numerical proportions, which would repeat themselves at each numeration. And it is also possible that external influences may in various ways affect such numerical proportions.
We may add also that, in investigations of this kind, other circumstances should be taken into consideration. Thus, in the case of endemic or epidemic disease, the births which furnish the statistics fluctuate, and the stability of the numbers, in consequence, is modified by these exceptional occurrences.
The numbers (Oesterlen) which are based upon the population of half Europe, are amongst the widest of statistical data, and furnish information of the highest value.
They represent 59,350,000 births. These showed an excess of male births. The proportions were 106.3 boys to 100 girls. Of course, these numbers refer to the new-born, and must necessarily be very much altered by the age of puberty. In fact, the powerful influences which come into play in the life after birth would very considerably affect the former of the above numbers. This is, however, a matter for further statistical investigation, and of little importance in our present inquiry. The numbers (Oesterlen) are in this respect very remarkable: the average of the total number of births in the various states corresponds very nearly with the numbers in the several states, or at least shows no difference worthy of consideration. In the single states, the proportion of boys to 100 girls varied from 105.2 to 107.2. Thus the proportion of the number of male individuals born to the number of females very nearly corresponded with the proportion shown by the total of all countries enumerated. Statistics derived from the genealogies of Court calendars gave (according to Kisch) 107.7 boys to 100 girls.
I am prompted here to quote also the statistical numbers given in Hensen’s work, which have been taken from Darwin’s ‘Descent of Man.’ Of pigs, rabbits, and pigeons, more males are born than females. For every 100 mares, 99.4 horses are born. In the case of greyhounds, 110 dogs are born for every 100 bitches. Of horned cattle 94.4 males, of poultry 94.7 males are born for every 100 females. The degree of accuracy and the limits of error which here remain undefined, make fluctuations easily perceptible. The mistakes, also, which may be made in such cases, are not always the same.
Statistics have been in many other ways called in to assist in the discussion of the question before us. In the early decades of the present century a question was raised—what was the effect upon the relative number of births of male or female individuals when the parents were of like or unlike ages?
Hofacker, in the year 1828, and Sadler (an Englishman), in the year 1830, attempted to solve this problem, and found adherents for their theories based upon numerical returns. But the Frenchman, Girou (Paris, 1838), appeared as an opponent of their views, also supporting his opinions by numbers obtained in the same manner, probably, as those of Hofacker and Sadler.
I shall not here reproduce the tables which were constructed for the discussion of this question. Any one who occupies himself with these questions can refer to the respective technical works, and I shall content myself with mentioning some of the results. If the man is older than the woman, more boys will be born. According to Sadler, the statistics showed even 121.4 boys for 100 girls.
If both the parents are of the same age, fewer boys than girls will be born. According to Sadler, in this case for every 100 girls only 94.8 boys are born. But if the woman is older than the man, an excess of girls in the family is the result. According to the two above-mentioned authors, when the mother is older than the father the proportions are: 86.5 boys to 100 girls.
Similar numbers collected by other specialists differ not inconsiderably from those given by Sadler. Regarding the proportions of male and female births as affected by the respective ages of the parents, Sadler’s numbers show the widest differences of all. Breslau and Noirot have arrived at numerical results so different, though less than Sadler’s, that no thoroughly reliable conclusions can be based upon them. Wall confesses himself an adherent of this law, and lays down the principle that in the intercourse of two quite young parents the male sex tends to predominate. If, on the contrary, the age of the man is distinctly greater than that of the woman, he insists on the excess of females amongst the new-born. The French breeder Girou de Buzareingues is disposed in many respects to support the theory of the influence of difference of age in the parents upon sex of offspring; but, also, on the strength of his own experiences in breeding, is partially opposed to it. According to his theory, he also takes into consideration the character, the food, etc., of the parents, and would have regard to their size and strength. In this way he gave his theory a much wider range. He mentions a great number of facts which he observed in the human subject. He outlines the expenditure of force, mental and physical, entailed on the parents by their occupation, and then sets forth ten very precise particulars from which, in any given case, the sex of the offspring which will result from the wedlock in question may be known. The following cases from Girou may be mentioned. A vigorous man married a corpulent, melancholy, elderly blonde. Seven daughters were the result of the marriage, all of them resembling their father and grandfather. Many similar cases are mentioned by Girou, all of which may be found of interest to the reader, if he be inclined to regard preponderance of temperament, or physical disposition for procreation of the species as important factors. Included in his repertoire of anecdotes are many interesting and piquant details respecting the results of the pairing of dissimilar temperaments which might be quoted, were it not that this would lead us too far from our subject, and also be of no service in the present inquiry.
Bidder is in many respects inclined to give his assent to the theories of his predecessors, and states that women who bear their first child between the ages of twenty and twenty-one produce more girls than boys (Düsing). The older the woman is at the time of her first parturition, the greater number of male births. An excess of male births will occur in the case of those who first give birth to children between the ages of thirty and forty (Eckhardt). Ahlfeld insists that this is a universal rule in the case of women who become pregnant in later years. A great number of specialists are of this opinion, and apply the data afforded by statistics to support it in different ways.
The evidence of Stieda, Berner, and Birelli, and especially that of Wilkens, respecting the domesticated mammals, leads, however, to this conclusion, that the theories respecting the relative proportions of male and female births set forth by Sadler and Hofacker must either be given up or their value considerably discounted.
Specialists are also to be found who, in order to explain this theory, have availed themselves of Darwin’s law, and in a certain measure the results admit of this explanation.
The older parent, who evidently under such normal circumstances as might be anticipated has a shorter time to live than the younger individual, his consort, naturally in the struggle for life, makes an effort for the preservation of his sex. Accordingly, the elderly husband of a young wife, or vice versâ, the elderly wife of a young husband, will make an effort to preserve the sex which is first threatened with death, but which may at least be replaced by a majority of births.
In so far as these theories are mere calculations and results which have originated from comparisons of numbers (the numbers themselves being in many cases of no practical value), the conclusions reached may appear to be astonishing, and may be used to support either one view or another, or to contradict them. Only one fact appears to be certainly established, that, on an average, under normal circumstances, the number of male individuals of our population that are born exceeds the number of females. The difference amounts to a small and variable number per cent., but in the case of the new-born, the excess is on the side of the males. (Süssmilch.)