Schenk's Theory: The Determination of Sex

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Preface

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 labour was long, and engaged my attention for years. And yet, amidst my continuous labours 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

PREPACB \\ 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 labours. The observations that have been recorded by

PREFACE. 7

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.

THE

DETERMINATION OF SEX.

. CHAPTER I.

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 recognised 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 to SCHENK'S THEORY.

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 connexion 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 cellsegmentation of an ovum. As soon as some of

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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 later 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 favourably 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 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 peopleis amongst whom there was none of that wandering about the world which characterises 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 favourable years, when food was cheap, the births showed an excess of girls. Under unfavourable 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 were 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 unimpeachi6 SCHENK'S THEORY,

able result of such investigations is renderecl.|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 I05'2 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) 1077 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 bom than females* For every 100 mares, 99*4 horses are born. In the case of greyhounds, no dogs are born for every 100 bitches. Of homed cattle 94*4 males, of poultry 947 males are born for every 100 females. The degree of accuracy and the limits of error which here re-

B

1 8 SCHENK':^ THEORY.

main 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, &c., 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 re. sembling 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 rSpertoire 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 (Dusing). 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 versd, 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 exceed 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 (Sussmilch).

Thus far we have given such data as statistics have furnished. These, it is true, belong principally to past epochs, and no new results of this sort have been used by statisticians. But it would be equally impossible to deduce from new statistics, or from old, or from both together, any law of nature affecting the question before us.

I shall proceed next to examine the further theories on this subject with which I have become acquainted from the perusal of the literature treating of it. With some of the works which I am about to mention I am acquainted at first hand. Others I know only from quotations found in various technical publications. I have not attempted to arrange my materials in any other way.

In the case of the most widely different branches of natural science, and whether the author's aim be descriptive or experimental, it is a common practice to commence with a glimpse at what has been said by the earliest writers. I shall begin in the same way. I shall, however, not take into consideration what has been at various times mere folk-Iore, and is only traditionally known, but shall limit myself to such traditions as have been preserved in writing. I liave, besides, already spoken above of suppositions respecting the origin of sex which appear to partake of the nature of myths. To these it was impossible to attach any importance. And the same must be said of other views which belong to the epoch of the Greek or Latin writers on natural science, and are so strange that they can be scarcely brought into any agreement with modern knowledge.

In Floss's work Das Weib in der Natur und Volkerkunde (Woman in Nature and Popular Tradition), are to be found the various speculations of different races respecting the origin of sex. Much of this folk-lore is of a distinctly surprising character, and calculated to afford the reader considerable amusement. For example, in Servia, if a man has a stye on his eye-lid he comes to the conclusion that his aunt is pregnant. If the stye is on the upper eye-lid, the child will be a male, if on the lower, a female.

Amongst the Asiatic races religious ceremonies, prayers, and similar expedients are considered efficacious, and capable of influencing the sex.

What question is there of the present day.

respecting which we can consult the literature of the ancients, that does not take us back to the writings of Hippocrates, Aristotle, or Galen, or to those of the old authors of those oriental races whom we regard as the earliest cultivated peoples? HijJJ^ocrates held that to produce a male, the generative material must be of a stronger quality. The future destiny of the male rendered it necessary that it should be constructed on a stouter foundation. He must be capable of a stronger development, and must, therefore, be a product of stronger elements alike on the father's and the mother's side. A second hypothesis was soon added to this primary one, but without any foundation of facts.

According to Aristotle, the woman supplied the primary material for the development of the future individual. It was the function of the man to give the impulse, in consequence of which the future individual came into being. Next followed the purely mythical theory, already mentioned, in which Anaxagoras believed. The much-sought-for origin of the future difference of sex in the various individuals was assigned to the right or left side of the organism. And Galen even concluded that the right side of the body was the warmer, and the left the colder, further claiming for the warmer side the privilege of producing male individuals.

Various notions respecting the origin of sex have been also accommodated to these primitive theories of the ancients, without resting upon any positive foundation. No evidence exists to show from whom they originated, nor how they were disseminated. Nevertheless, the historical connexion of these speculations justifies a reference to them, and various hypotheses of this kind will be found in a little publication of Dr. Heinrich Janke's (Stuttgart, 1896). The older literature on the subject of the generation of the sexes has been collected by His {Arckiv fur Anthropology Vol. IV., V.) In Das Weib in der Natur und Volkerkunde (Leipzig), Ploss has collected ample information concerning both ancient and modern ideas on this subject amongst the different races of mankind. The procreative elements, furnished by the male and female organs, after their mixture, compete with each other, by virtue of their inherent forces, for the mastery. In this conflict, if the male molecules are the more numerous, a male results. On the contrary, if the female molecules ar^ more numerous, the result is a female, Nicholaus Venette ascribes the difference of sex to the earliest phases of the life of the ovule.

The following aspect of the origin of sex is not without interest, although the theory rests on somewhat insufficient foundations, and is applicable, in the first instance, only to those creatures which produce but a single individual at a birth. Many creatures, and especially certain species of birds, present this phenomenon ; they lay in a single month two eggs. Of these, one is male, the other female. In this way a provision is made for the equal increase, in each respective month, of both sexes. In the case of man, it would, in accordance with this, be anticipated that naturally an equal number of ova of either sex would be produced by a single individual.

This would lead to the supposition that, in the case of the human female, in one month a male ovule would reach its perfect development, and in the next month, anterior to the occurrence of the menses, a female ovule. Thus the ovary of the human female would contain in one month a male ovum capable of fecundation, and in the following month a similar female ovum.

After a woman had once given birth to a child it would then be possible to form a correct idea of the distribution of the ova of the different sexes. The month of birth and the sex of the new-born child would be known, and starting from the datum that it would be the turn of the ovum of the next month to develop the opposite sex, it would be possible to fix the given month in which an individual of the male or female sex should be developed (Dupuys).

To these less general explanations of the origin of sex belong certain very startling theories dealing with the question before us. These notions are set forth at great length in theoretical explanations put in the shape of popular expositions. According to these views a single cell of the male or female reproductive glands is regarded as a sort of complicated compound structure that might be compared to a spherical world, in which thousands of primal individuals are contained, from whose powerful and secret activity results the formation of male or female individuals. (Hinz. Neusalz am Oder, 1897.)

Another very common opinion is that the seasons (Dusing;), the climate, and other loca^l circumstances have an effect in determining the sex of the embryo. If the data supplied by Birelli, Bemer, C. F. Vilson and Felkin and many other authors be taken together, it appears that the different zones of the earth's surface are not without influence in the production of one sex rather than the other. More boys appear to be born in the north, in the warmer south more girls.

Felkin and Vilson adduce the following instance from the south of Egypt: — The Wagandas, a warlike race, kill the men and the old women of their conquered foes. The children, girls, and young women they lead into captivity. On one occasion 480 of the women gave birth to children on their march. Of the new-born 79 were boys, 403 girls. This incident led the author to pay further attention to the subject on the East Coast of Africa and in the Soudan. Everywhere he found the anticipation of an excess of girls supported and confirmed In fact his investigations of the phenomenon led him to formulate and advocate a law that the better nourished and superior parent tends to produce the opposite sex.

In this case the women are in an inferior position, and in consequence worse nourished and practically exhausted. Amongst other neighbouring races, where they live peaceably and domestically, the difference between the number of new-born boys and girls is not a very great one, although a small average appears in favour of the girls. The influence of different phases of the moon has also been taken into consideration, and has been described as so effective, that some have even attempted to prognosticate by these means the sex of a second child after the birth of a first (Lioy).

From Vilson's statement, that the sex of the worse-fed parent perpetuates itself, a theory has been deduced which has been described as cross-heredity of sex {Gekreuzte GesckUchtsvererbung). In accordance with this theory a prominent phenomenon would be that the individual parents were not in a position to propagate their own sex, but were yet under certain circumstances capable of reproducing the opposite sex. If the father were the stronger a girl would result from the next impregnation ; in the opposite case a boy. A great number of authors of renown, most of whom are mentioned in works dealing with these questions, are supporters of this theory.