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 theovule, 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 themselvesout 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 surroundingelements 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 favorablyaffect 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 ofopinion. 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 matterdistributed 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 highestscientific 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 sametime 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, areamongst 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 individualsborn 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 thequestion 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, moreboys 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, andlays 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 fromwhich, 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 hisrepertoireof 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, orvice 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 contradictthem. 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.)
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 theliterature 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-lore, and is only traditionally known, but shall limit myself to such traditions as have been preserved in writing. I have, 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 tothe 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 Ploss’s work ‘Das Weib in der Natur and Völkerkunde’ (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 eyelid he comes to the conclusion that his aunt is pregnant. If the stye is on the upper eyelid, 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 literatureof 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? Hippocrates 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 whichAnaxagoras 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 connection 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 hasbeen collected by His. (Archiv für Anthropologie, Vol. IV. V.) In ‘Das Weib in der Natur and Völkerkunde’ (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 are 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, onlyto 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 bepossible 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 activityresults the formation of male or female individuals. (Hinz. Neusalz am Oder, 1897.)
Another very common opinion is that the seasons (Düsing), the climate, and other local circumstances, have an effect in determining the sex of the embryo. If the data supplied by Birelli, Berner, 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 reproduction 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 neighboring 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 favor 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 meansthe 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 ascross-heredity of sex(Gekreuzte Geschlechtsvererbung). 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.
We have already mentioned that there are some who regard the act of generation as aconflict in consequence of which the sex of the elder parent, whether father or mother, will be reproduced, so that the sex in question may maintain its position. Similarly, in the case of the so-called cross-heredity of sex there seems to be a conflict for the preservation of the opposite sex. What conception we are to form of this conflict seems a difficult question. Any measure of the greater or less excitability of the centers during the act of generation (which might be determined in the case of animals) is not easily to be reached with any degree of probable correctness; and how much less any numerical index which would express the differences of excitability, of strength, and so forth, which might be developed during the conflict of the opposite sexes. The theory of the cross-heredity of sex rests upon the phenomenon that those female animals which are impregnated by sexually inferior and older males, whose capacity for reproduction must be consideredas inferior to that of the females, produce more male than female individuals.
When a queen-bee lays male eggs, it is often asserted that these are not yet fecundated. It is only after they have been impregnated by the male that the female individuals appear. That is to say, after the male influence has had its effect, the causes which lead to the development of the female make themselves apparent, in accordance with the theory of the cross-heredity of sex. Previously, this influence was wanting, and, in consequence, only male individuals resulted from the eggs.
From the unfructified eggs of Daphnia (water-flea) many individuals are at once developed, and in numbers so great as to be surprising. According to Heincke, female individuals can be developed from eggs which have not been fructified, but have been well nourished.
Dr. Clarke, a medical man of Detroit, is of opinion that in the commixture of the elements, which serve as the basis of the future individual, some external force is also embodied. Then the situation would be something like this: there are two elemental forms, which, in impregnation, are brought near each other, and their union actually effected; of these the female ovum has the function of occasioning a male offspring, and the male element that of occasioning a female. In this act a conflict is supposed to take place, in which each sex strives for the production of the opposite sex. But here there would be also an expenditure of force on behalf of its own sex. This appears to be a labor of love on the part of the sexually more ardent consort, to which he or she finds himself or herself prompted by nature for the sake of the weaker female or male sex, but at the same time without any conscious volition of accomplishing an expenditure of power orenergy in this (reflex) act. Richarz affirms that it is the function of the man to produce a higher degree of organization during the development in the germ. But if the productive force of the mother is more energetic, and exerts a greater influence, the result is a boy. When, on the contrary, the generative force excited in the mother by successful fecundation is weaker, the fecundated germ does not attain the masculine sex.
Cases from married life are mentioned by different authors in which the husband, partly in consequence of sexual debility, occasioned by repeated seminal emissions on previous occasions, partly in consequence of advanced age, and besides, also, through spermatic secretion (Samensecretion), was scarcely capable of performing his conjugal duties, nevertheless, pregnancy ensued, which after nine months resulted in the birth of a boy. In these cases the mother would have decided the sex of the child. But one is moreinclined to explain the origin and development of a boy in these cases by the law of cross-heredity of sex. It may certainly be concluded from these cases that a man, from whom it might have been supposed that no procreative substance was to be had, although he can be reckoned amongst the patriarchs of his species, may yet sometimes be able to boast that he has left male offspring to be his direct heir.
On the other hand, Guttceit relates that a man, during the period anterior to his having a mistress, and whilst he was entirely at the service of his wife, begot only daughters. When, however, he limited the time which he spent with his wife by devoting a part to a mistress, his wife presented him with male offspring. This is a case which might be explained by the law of cross-heredity of sex.
Serious surgical interference with the female certainly has an effect upon fecundation. At least, pregnancy appears to bepostponed after the more difficult operations. If, however, impregnation takes place, either male or female offspring may be anticipated. This contradicts the theory of cross-heredity of sex, according to which only individuals of one sex should appear, if one ovary has been removed.
Facts which have been brought to light by experiments with animals, and by observation in the human subject, tend to give the theory of cross-heredity of sex a higher value. But under the same circumstances, other phenomena present themselves to observation which appear to render some of the postulates of this theory untenable. Various diseases which are diagnosed by medical men as organic disorders, but which do not interfere with the power of reproduction, are apparently without influence on the sex of the offspring, and also without influence upon a striking prevalence of one or the other sex.
Richarz assigns all the power to the fecundated female individual. He thus raises the culminating point of the female power of reproduction to a height above that which other specialists will allow. In this he is in complete disagreement with Roth, to whom he is also opposed in other directions. Within certain individual limits (amongst which is not to be included a diminution of capacity in consequence of the necessary periodical functional impulses), the female organism discharges its functions the more frequently and the more perfectly the less often it is called into operation, and,e contra, the less frequently and the less perfectly the more often it is called into operation. According to Vernich, very long intervals between successive pregnancies disturb the progressive increase in the weight of the children less than very short ones.
One may, without being afraid of making any great mistake, at any rate in the case ofwomen who bear many children, make the same assertion respecting the constantly increasing probability of male offspring, as respecting the increase of weight.
The beneficial effect of a fairly long fallow season upon these periodically acting organs is revealed in this way among others, that, often enough, in consequence of prolonged rest and recovery of strength, the female generative organs, after frequent still births, became capable of producing healthy children. (Richarz.)
The fundamental law of crossing is supported by this author in every direction. He recommends it as revivifying the blood and tissues, in order to combat the evil effects of inbreeding, the exhaustion of normal and healthy conditions, and as a preventative against the appearance of degeneration and decay. A similar relation between the sexes exists in their functions for the continuation of the species.
If an attempt be made (Richarz) to explain the different facts observed, in accordance with the theory in question, no insuperable contradictions will be met with. The general excess of male births, their corresponding increase during the loss of many men in war (a loss of distinctly stronger men), the high proportion of male births in the case of mothers who produce their first-born at a comparatively late age, the same high proportion where polygamy prevails, and, further, the diminution of male births in the case of unmarried mothers, which should not be overlooked,—all these phenomena are declared to be in accord with Richarz’s views.
We will proceed here to give a brief sketch of Richarz’s opinion. Ribot powerfully supports it in every particular from his own experience and from historical data. The primary impulse upon which the whole process of generation depends lies in the organsof the mother. Here lies also the substratum in which is, as it were, the center of gravity of the special generative process.
The function of the male sex is to evoke from the feminine substratum an organism, or, more strictly speaking, to occasion a change in the germ. If the mother’s generative capacity reaches the highest point the result is a boy, who in external appearance resembles his mother.
If, however, it happens that the forces which act in the mother are inferior to those of the father, the infant will be a female. She will resemble her father, and will also inherit her father’s temperament. Sex is not a transmissible attribute inherited directly from the parents. Personal appearance and other characteristics will on the whole correspond rather more with one of the parents than with the other. Yet in every case the influence of the other parent will make itself felt, and will in many respects exercisea modifying influence over external appearance and other characteristics.
These views have been attacked by Roth, who declares himself against Richarz’s hypotheses. His objections are contained in a work entitled ‘The Phenomena of Heredity’ (Ueber die Thatsachen der Vererbung). He directly attacks the theory of cross-heredity of sex, and according to his theory claims for each parent an equal share in the formation of the future individual, at least in the earliest stages. Fecundation, according to Roth, would at once be effective in determining the sex of the future individual.
We shall have occasion hereafter to speak of the observations which Mayerhofer has made upon the origin of sex. Here we shall mention only a single fact. This is a result of his experiments with animals, and seems to have a relation to the theory of cross-heredity of sex.
Ewes impregnated by a powerful ram bearmore males than females, so long as the ram is in possession of his full forces. After a time the ram has to perform his functions repeatedly during a few days, as great numbers of the ewes are rutting. The fatigued or exhausted ram then begets only females.
Next the number of rutting ewes diminishes. The ram gradually recovers his strength. Whilst constantly employing it with the remaining rutting ewes he again begets male individuals. Now, according to the rule of cross-heredity of sex, the number of females ought to be greatest at the outset, because we here have a male of exceptional force. When the ram is exhausted, according to the theory of cross sexual heredity the males ought to be more numerous. It appears, therefore, that in this experiment of Mayerhofer’s we have something which remains in want of explanation. We shall presently have occasion to speak more fully of the facts which this author communicatesrespecting the origin of sex in man, and will then return to this subject.
The information which we have concerning a stallion (Sir Hercules) belonging to the stud of Count Lehndorff deserves attention. This stallion was twenty-six years old, and had to cover twenty-three mares. The result was twenty-four foals of the male sex. This case of the ardent mares and the old stallion can be explained by the theory of cross-heredity of sex.
Particular attention should be here directed to a phenomenon which seems to imply that a sexually exhausted individual always has his advantage of propagating his own sex secured. It is a sort of fulfilment of duty on the part of a strong female animal when her litter shows a majority of male individuals, or male individuals only. In this connection may be mentioned the facts communicated by Settegast, Nathusius-Hundisburg, and De la Tellais, who arrived at their resultsfrom experiments upon the proportions of the sexes of the offspring of the domesticated mammalia.
Attempts to solve the problem of the origin of difference of sex by means of experiments have been numerous. So early as the last century Platz attempted to carry out experiments with living animals.
The temperaments of the breeding couple ought to be concordant. Both should be either of warm or cool temperament. Warmth and moisture are primary conditions of fertility, not in plants alone, but amongst the animals also; and (as Mayoor Zsigmond, of Kaschau, proclaimed in 1723) represent the primary conditions of the possibility of a conception.
The warm element belongs to the man; the moist to the woman. Where both qualities are to be found in both, offspring may also be anticipated. But if this be not the case,for example, if the man’s warmth does not accord with that of his wife, but is of a higher degree, then he can beget boys. If he be not so warm, he must, if he wishes for sons, make a distinct alteration in his diet. According to the prescription given, he ought to lead a regular life and to limit himself strictly to warm and dry aliments. The temperament of the woman is often ardent and dry. In this state it must be regarded as unfitted for the development of an embryo. Befitting food would not be without an influence upon the alteration of temperament. Respecting this, experiments had proved this much, that a suitable change of diet can exercise a salutary influence over the temperament. A woman who was in the highest degree beautiful in face and in every part comely had a temperament which would accord with that of any man.
Then comes the theory of the allotment of the male and female in man, and in all thevertebrata, to the right and left sides of organs of generation. This is a theory which is being always brought forward, even by the most recent writers, some of whom go so far as actually to wish to support it by experiments.
Thus the excision of one or the other of the testicles of the male is recommended in order that the owner may be able to breed the sex which he desires. It still remains, in order to effect the artificial determination of the sex, that the female should also play her part correctly, so that the semen of the male may be conveyed to an ovule from the required ovary. An effort was accordingly made to secure intercourse in such a manner that the semen of the male might be delivered in a certain direction in agreement with the anatomical position of the duct which was to lead the seed into the required ovary. But it was practically difficult to settle what position in the intercourse was the rightone. Experience proved that in a certain case on two successive occasions male individuals were born when the impregnation had been so contrived that the semen should enter the right ovary. Therefore the left ovary was for female offspring. It is not our concern to enter into further explanations of these occurrences. Only this much may be said, that experiments have been constantly made which might lead to some conclusive solution of these questions, without any result having been obtained.
A publication appeared in the year 1786 dealing with the above-mentioned theory, and at the time attracted much attention. It has now become difficult to procure, and is often mentioned on account of its containing much that is valuable for influencing sex, both amongst men and animals, that has been gathered from all the authors of the previouscentury, and more especially from all the ancient authors who had written on this subject.
The author was J. Ch. Hencke, organist at Hildesheim, and the title of his book, ‘The Secret of Nature Completely Discovered, both in the Procreation of Man, and for the absolute choice of the Sex of Children.’ Brunswick, 1786. (Völlig entdecktes Geheimniss der Natur, sowohl in der Erzeugung des Menschen als auch in der willkürlichen Wahl des Geschlechts der Kinder.Braunschweig, 1786.) The author relies upon exploded theories, according to which the offspring is evolved, as it were, out of a mixture of the generative secretions of the two sexes, and can be induced to develop into either a male or female individual. Thus the sex is not previously determined, only in the course of its development out of the developing mass, which consists of a mixture of male and female generative secretions, distinctive sexual characteristicsmake their appearance, according to the predominance of the male or female portion of the mixture. But here, also, the old theory is set forth very precisely. The generative matter of the right testicle serves to fructify ova from which males are developed, that of the left testicle is used to fructify and develop female ova. Similarly, the tenet is propounded that the right ovary contains male ova and the left such only as will, when developed, produce female offspring.
These doctrines, as a basis for the breeding of animals, Hencke had discovered by castrating swine, dogs, and rabbits. Thus it happened that a boar, who, after castration, had only the left testicle, twice running bred with a sow female young only. Similar phenomena occurred with other animals, so that this method was recommended by the author to the breeders of his time. But ithappened, also, that a surgeon upon opening the body of a woman who had had sons only and never a single daughter, found the left ovary very thin and withered, so that it was hardly possible that it could serve for the development of a new individual. On the contrary, the right ovary was in a normal condition. It now remained only to discover some device for man, by which he might be able, during the act of generation, to avail himself of the discoveries thus made, so as to obtain the result of an absolute choice of the sex of the offspring. The ligation of one of the testicles was Hencke’s infallible remedy. When this severe proceeding proved impracticable, in its place was substituted an elevation of the testicle by means of its suspending muscle (the cremaster). Under certain conditions this takes place of itself in particular positions, and was accordingly recommended as an established proceeding for men.
One other conclusion of Hencke’s deserves particular mention. He was bold enough not only to assert that the right and left sexual glands served exclusively for the generation of male and female individuals, respectively, but also asserted that the generative matter from the right or left gland of one parent was productive only when united with that of the same gland of the other parent. His counsels were not for such persons as are too heated, too ardent. “For young, hot, hasty men,” he says, “who are altogether without consideration, I am not writing; but for chaste married people, and especially for those to whom the production of a child of one or the other sex is a matter of importance.”
Couteau established the fact that each seminal duct had its own orifice, through which the semen was poured into the urethra. This fact was in his days of the greatest importance,as it prevented any mixture of the semen of a man’s two testicles. Hencke firmly insisted that the semen was discharged by one testicle or seminal vesicle alone, in the case when the testicle was raised up. But we need not here follow further Hencke’s theories which he deduced from his own experiments. In the present day these theories will satisfy no one. Results which have been obtained either after ovariotomy, or after the extirpation of testicles, have made us perfectly certain about the value of one or the other generative gland for the production of the male or female sex. The case of Schatz, which has been also pointed to us as important in other specialist works, may not be uninteresting here. The left ovary of a young girl was removed, together with a portion of the left tube, and the right ovary, also, with the exception of a margin of about two millimetres’ breadth. When she was married she gave birth to a girl, whereas a boyshould have been expected, seeing that only male offspring were to be produced by the right ovary.
Scarcely any work that lies before us on this subject is so much regarded as that of Hencke. At the same time, and although it had in its day the widest circulation, it frequently met with the most unqualified condemnation. Dr. von Seligson, in his discourse before the Society of Medical Practitioners at Moscow (1895), on the subject of influencing the development of sex, in connection with Hencke’s theory, attached value to a great number of experiments tending to support the old view. It was, however, admitted that by a departure of nature from the ordinary law (somewhat resembling a transposition of the viscera) male or female ova might occur in the respectively opposite ovaries.
De Bay, who was opposed to the theory of the anteriorly-developed sexual products ofthe right and left ovaries, asserts that the quality of the generative products depends upon the quantity of nitrogen existing in the chemical composition of the ovum and the semen. A large proportion of nitrogen in the ovum occasions the development of a girl. If, on the contrary, the semen contains a great quantity of nitrogen, a male individual will result. To determine the proportion of nitrogen, or to give it scientific value in such cases, seems to be a difficult matter.
Mention is also made of cases of tubal pregnancy in which the sex was determined, and an effort has been made here, also, to find some support for the theory of the existence of sex in the ovum whilst in the ovary on the right or left side. Fourteen of these tubal pregnancies, described by different authors, showed boys on the right and girls on the left side. (Seligson.) In such anomalouscases where the embryo has developed itself in the Fallopian tube, and has not reached the uterine cavity, there is no doubt that the developed ovum originated in the ovary of the side on which it was found.
Efforts are made to confute the different objections raised in many quarters. The mention made by the traveler, Peter Kolben, of the practice of cutting out one testicle, which is the custom of certain African tribes (this is contradicted by Le Vaillant [1784], and by Fritsch [1880]), and the accounts of Otto Finsch, may not deserve credit, as they rest upon assertions made by other persons. Accounts are further given, drawn from medical experience, of men who, after prolonged orchitis, with consequent occlusion of the vas deferens, begot only children of one sex, or in other cases were unable to induce pregnancy. Also the discharge of semen was asserted not to take place from both spermatic ducts at the same time. After manydigressions, Seligson in the end adheres to Hencke’s theory on no sufficient grounds, and then bases on that theory a method, upon which I shall not here pass judgment, but merely mention it without describing it.
At all events, there can be no question of a compression of the spermatic cord in any way, for it could not be accomplished, either manually or with the aid of various kinds of apparatus, without giving rise to excessive pain.
In this case, as Hencke in his time explained, the cremaster muscle raises the testicle up towards the inguinal canal. At complete erection the testicle is drawn up and pressed against the inguinal ring. This gives more favorable conditions for leading the semen forward from this one of the two testicles; and this portion of the semen is used for impregnation, to which end also a favorable attitude and a free passage into the ovary must be provided. According tothe views of the author, this method, if adopted in procreation, will lead to the desired result of producing a given sex. Exceptions are admitted. Exceptions occurred in five families with twenty-three children. The author clings firmly to his theory that each testicle possesses its own special spermatozoa and each ovary its special ova, in which a given sex is already in existence, and from which in fruitful intercourse male or female individuals originate.
Next after a number of theories which have been current on this subject, we reach some others, to which more or less value has been attributed. Morello attached weight to the concentration of the semen. Thin, liquid semen was to be favorable to the production of females; thick semen produced males. According to modern theories, based upon observation of invertebrate animals (O. Hertwig, Balfour, Landois, Minot, and others), it appearsimprobable that this position can be maintained. The supporters of this theory assert that a single spermatozoon suffices for the fertilization of an ovule, or to develop the ovum into a so-called “oosperm,” that is to say, to form a really fertilized ovum. (Perhaps the excess of semen serves for the earliest nutritive processes of the ovum; which would, however, be difficult to prove.) This fact has been also confirmed in the case of the higher animals, and it might be in a similar manner brought to an issue in the case of man. However, observations of this kind have not yet proved possible with man. But in the case when several spermatozoa penetrate the interior of a single ovum, anomalies in the process of development result from the formation of several nuclei. Such ova, also, perhaps in consequence of excess of semen, are very often aborted and perish.
In order to throw light on the causes determining sex, Pflüger (in connection withresults obtained by Born, which will be cited later) attempted to determine the relative numbers of the sexes, under normal conditions, in the case of the frog (Rana fusca). The numbers were taken by his pupils, A. von Griesheim and Dr. W. Kochs. The identification of the sex was made with a microscope under the supervision of Pflüger. According to Pflüger the Graafian follicles are easily identified with the aid of a microscope, if they are not in their earliest stage. They contain an ovum with a scanty yolk and large germinal vesicles with germinal markings. The whole is surrounded by connective tissue.
According to Pflüger, the epithelium is wanting in such very young follicles. In these frogs after their metamorphosis the testicle consists of tubes, with multinuclear epithelia, and is easily distinguishable from the always large ovaries of the tadpoles. By different concentrations of semen, Pflügerattempted to influence the proportion between the male and female sexes.
According to Pflüger, there are normally found amongst frogs in a state of nature 36.3 per cent. males, and 63.7 per cent. females. With thinner or thicker semen, the average number can be altered. With thin semen Pflüger obtained 27.3 males and 72.7 females per cent. With concentrated semen he obtained 39.4 males, and 60.6 females. Pflüger carried out some other experiments, and came to the conclusion that the concentration of the semen or the extract from the testicles exercised either a very small influence or no influence at all upon the sex. When he took an average result from all his experiments, he found that out of 806 frogs which he raised, 288 were males. Whilst the normal proportion of the males developed freely under natural conditions was 36.3 per cent., that reached by experiment was 35.7 per cent. It should be here remarked thatamong the tadpoles many are found whose sex is not yet determined. They are in a hermaphrodite condition, out of which they develop into either males or females.
Robin, the well-known French histologist, made the question of the origin of sex the subject of an extensive inquiry. His investigations start from the following point:—In warm climates the whole quantity of blood in the inhabitants is less than in temperate zones. The process of respiration in the inhabitants of warm climates is also not so free as in the case of those who inhabit temperate or cold zones.
From this it would seem that some process connected with nutrition, and with the passage of nourishment into the blood, is the cause of the number of male births being greater in the cold zones than it is in the temperate zones, or in the inhabited regionslying nearer to the equator. It would follow from these considerations, that if the women were subjected to such a régime as would materially affect their respiration and the quality of their blood, more boys than girls, or the contrary, might be bred. If so, breathing an atmosphere containing more oxygen, with a corresponding diet, would be the right receipt for producing in the woman such a basis that in the course of development the male generative organs (which Robin considers the anatomically more perfectly developed) might be evolved instead of the female. According to Robin, the male sexual apparatus in comparison with that of the female is provided with the more perfectly developed character. Robin further insists that strong men will beget more male individuals. Further, that a woman who indulges in sexual intercourse somewhat seldom has female children; and that voluptuous women, who are fruitful, generally bear boys. A number of experimentswith domesticated mammalia are adduced in support of this view.
Hegar teaches that in the case of a merely rudimentary development of the germinal gland either sex is developed.
With the views of Robin may be connected also other suggestions regarding the food of the parents. These have been tried both with men and animals. But we shall not here go further into them. Nor shall we mention the different kinds of food or drink which have been employed, whether by men or women, to produce a greater sexual activity.
The eminent naturalist Born, of Breslau, made a long series of experiments, which are of the highest interest in reference to the doctrine of the origin of sex. It is easy to fertilize frogs’ eggs artificially. The ripe eggs aretaken directly from the female, and the testicles of the male rubbed with water. This fluid, which now contains spermatozoa, serves to fertilize the eggs. Spallenzani had already undertaken artificial fructification. Born observed, during his study of the course of development, that the effect of his breeding as regarded sex was to produce 95 per cent. of females. This number is evidently so remarkable that it ought to secure particular attention. No such extreme contrast between the numbers of males and females is to be found amongst the frogs that develop freely under natural circumstances. It seemed to Born that his result was to be referred to insufficient nourishment, and that the tadpoles, being somewhat unfavorably circumstanced, had not been able to attain the development of the stronger sex. In this experiment on the evolution of sex it appeared that not only was there an excessive production of females, but that the other organs ofthe embryo and its whole constitution could be modified by means of nutrition. It is also to be observed respecting this most interesting experiment that many of the tadpoles perished of hunger. Now, the number of still-born males of the human species very much exceeds the number of still-born girls. The mortality amongst males is so great that the average is from 136 to 140 still-born boys to 100 still-born girls. An attempt has been made (Pflüger) to explain this phenomenon in the human subject on the ground that the tenacity of life in the female sex in the period of embryonal existence exceeded that of the male. Consequently, boys would more easily perish during development than girls. If this observation made with respect to human beings were applied to the tadpoles, it might also explain the high percentage which the females showed among the frogs. Very likely the male tadpoles possessed less capacity of resistance; or, in other words, were lesstenacious of life than the females. It will be understood that this view would apply only as a partial explanation of the facts set forth by Born.
In the artificial breeding of trout, which is conducted under cover, in which process the embryos which have crept out of the ovarian follicle are kept with the yolk-sacs in small reservoirs under a continuous flow of water, it is observed that single individuals develop themselves further. They lose their store of yolk with the yolk-sacs. In the course of their further development and nutrition they arrive only very slowly at the development of the internal generative organs. Even in a very advanced stage the sex is not yet so plainly indicated as in fish of the same size living free. Indeed, it is even affirmed by many persons of experience that in the artificial breeding of trout even those that have attained their full growth remain unfruitful andcannot be used for further breeding. (D’Audeville and Arens raised, in the case of trout, more females by dry impregnation.)
Here might be adduced also many other doctrines of greater or less interest respecting the theory of the origin of sexual distinction. Only in order that I may not introduce too much literary matter, I shall mention only a few of the more important and noticeable theories before I return once more to the experiments upon the influence of food upon the development of sex. Janke’s work (small edition), published at Stuttgart in 1896, furnishes a synopsis of the literary work done, as do other books which treat of this subject.
Mons. Thury, professor at Geneva, published at Leipzig, in the year 1863, a book on the law of breeding the sexes, which,on account of its contents, attracted great attention. In this work the author, after a number of successful experiments and other investigations, shows how an influence may be exerted over the sex of plants, animals, and men.
This work stirred me up to the endeavor to devote myself to this question, so far as that might be possible. I shall give a short sketch of Thury’s work, together with the critical revision of it by Dr. H. A. Pagenstecher, of Heidelberg.
The doctrine respecting the origin of sex in cattle was laid down by Thury from his own investigations. The principal point in his doctrine of the origin of sex in animals he considers to be the condition of the ovum at the time when it is fertilized. If the ovum has reached the stage of ripeness, which may be described as an advanced stage, we may expect to have, after fertilization has taken place, a male individual, which will developitself out of the ovum. If, however, the ovum has reached only an imperfect state of ripeness when successful impregnation takes place, then no such powerful and perfect specimen of the race as the male is can be developed, and the result of such an ovum is always a female.
From this it follows that, according to Thury, the cause of sex lies in the ovum developing itself in the ovary, and the degree of its ripeness is the only factor in the development of one sex or the other.
It is not, however, shown what the systems are by which such an ovum can be correctly judged, so as to determine the different degrees of ripeness. We now know very well certain signs which appear upon the maturation of the ovum, of which we shall not say more here. Of these Thury could know nothing in 1863, because at that time they had not been discovered.
Thus the sex depends upon the ripeness of the female’s ovum at the time of its fecundation. In the case of its having reached the highest degree of ripeness, a male is the result. It is impossible for the ovum to attain a higher degree of ripeness. If the ovum of a human female has arrived at this supreme degree of ripeness, it has reached that stage in which it is capable of becoming the basis of the most perfect living creature which exists upon our globe.
Rutting is an external sign of the maturity of the ovum amongst the lower animals. When, during the rutting period, an ovum is detached from the ovary, and passes through the Fallopian tubes to the cavity of the uterus, the fructification can take place at the beginning of the rutting period. At this period its ripeness is not so far advanced. The result of the development of such an ovum is a female. But when the fecundation has taken place at the end of the ruttingperiod, the ovum has reached its highest degree of development, and, if effectively fecundated, it will become a male. It follows that the signs of rutting should be carefully studied, as in fact is habitually done by practical farmers. The duration of the rutting period and the influences which affect fertilization should be accurately known in order to lead to any practical result.
Females at their first conception would usually produce, or would be particularly disposed to produce, female individuals. Experiments succeed better with such as have often produced young. In their case the symptoms which indicate the commencement or the conclusion of the rutting are much more easily determined, so that they are better adapted for these experiments.
We know well that in the case of the lower animals when rutting, as in the case of the human female during menstruation, anovum is liberated from the follicle in the ovary, and ordinarily passes away in the menstrual discharge. In fact, a follicle of the ovary bursts, and, to be precise, that one which protrudes most beyond the surface of the ovary. This bursting of the follicle has not actually been observed. But that this event takes place there can be no doubt, for the locality of the fissure is perceptible, and the ovum is found either at hand on the ovary, or else on the fimbria. The increase of fluid in the follicle of the ovary, and the excessive charge of blood in the vessels on the walls of the follicle, seem to be, without any actual contraction taking place, the physiological causes of the freeing of the ovum from the follicle, so that it may come in contact with the semen. Ovulation can take place without intercourse. But sexual intercourse can also favor ovulation; at least, it appears to facilitate the separation of the ovum from the ovary.
Bischoff made known the fact of the separation of the ovum from the follicle. He showed that the presence of sperm in the feminine organs of generation of the animals was indifferent, that the rutting of the animal was the index of the ripeness of the ovum. Eimer, Beneke, Van Bamecke, and Hensen, call attention to the phenomenon which is observed in the case of bats, who for a whole month before the detachment of the ovum from the follicle have their uteri full of semen.
These processes which take place at rutting time are attended with sexual excitement and congestion of the external genitals. It is not, however, necessary that these processes should in the case of all animals occur at the same time as ovulation. If rutting animals are restrained from sexual intercourse, the sexual excitement of the female passes off; but the symptoms of rutting againmake their appearance after a time. These are the phenomena of the so-called rutting season.
This rutting season lasts with sheep fourteen days, with swine fifteen to eighteen days; with cows, horses, and apes four weeks. It corresponds to the menstruation of the human female (Hensen). Many bitches admit the dog only when six or seven days have elapsed since the issue of blood. In the case of many animals rutting is marked by a flow of blood from the genitals. This is the case with apes, bitches, swine, and many other mammalia.
Under these circumstances, the symptoms of rutting are sufficiently distinctly marked to make it possible, as Thury suggests, to determine the advanced state of ripeness or its commencement in the ova. But it is scarcely possible to say when the period of ripeness commenced in this ovum or that.An ovum which had begun to ripen early may, at the beginning of the rutting time, have attained to the condition of a male-producing ovum. At the same time, others which are fertilized at the conclusion of the rutting, but had begun to ripen comparatively late, may, at the end of the rutting time, not yet have advanced far enough to be able to develop male individuals.
Thury bases his doctrine on a number of phenomena of the vegetable and animal world, and upon various experiences in the case of man. He also adduces many statistical data in explanation and support of his theory.
The observations on plants make it indisputably clear that all the circumstances which favor growth and ripening are favorable conditions for the development of male organs. If all these circumstances are lacking, female organs are produced.
Dark and cold, for instance, cause the male organs to perish. In recent times a great number of extended studies of the phenomena of vegetable life in this direction have appeared. I may mention more particularly the following experiments made by M. von Treskow in Gorlitz withArisæma(Verhandlungen des Botanischen Vereins der Provinz Brandenburg, 1895). This plant first produces male flowers. In the later year, when it has become larger, it produces female flowers. The transition from the male flowers of the early stage to the female flowers of the later stage can be hastened at pleasure by planting in rich garden mold and manuring with horn shavings. If, on the other hand, the plant be placed in poor, sandy soil, it reverts to the male flowers. The same author quotes in his essay a remark of Heyer’s (Halle, 1884), who declares that no sufficient observations exist respecting the influence which different situations exert over sex.