  In sexually differentiated individuals, the difference of sex is already apparent in the embryonal state of existence, not only in the exterior form, but also in the interior cellular rudiments which subsequently form the genital organs. In both, the earliest forms are of such a nature that, up to a certain period, it is impossible for investigations conducted with the means at present at our disposal to discover any distinction. Soon, however, after this, in such organisms as have a distinction of sex, elementary male and female forms of the organs of reproduction can be recognized developing themselves in the embryo out of the substratum of formative elements. Some of these remain in a rudimentary condition; others attain to complete development. These processes take place at a relatively early period. They do not seem to make their first appearance, as phenomena of vitality, in the course of the life-development of the cells of the ovum. But it is not improbable that, from the very outset, the ovule has a capacity to transfer (during the process of segmentation) to a corresponding cell-substance (out of which the generative organs will be subsequently developed) the force contained in the ovule, so that the cell-substance may afterwards take up the office of providing for the preservation of the species. The cells of the ovum derive this power from the protoplasma of the ovum, and retain it in a rudimentary form for one sex, whilst for the other they possess it in full measure. This energy is contained in the ovule itself in an unknown condition. In it lies the basis of the formation and development of the future sex. In close connection with this property of the ovule, lies another faculty, included in the It will be plain from this that the germ of the future sex must be sought in the first cell-segmentation of an ovum. As soon as some of the cells derived from the primary protoplasm of the ovum have developed themselves into genital cells, the other elements which have originated from the same ovum are in such a manner conditioned that, in the latter stages of their vitality, they adapt themselves, and, in short, adapt the properties inherent in all the cells, to the sex of the individual. According, as the ovum is male or female, so are also the cells which originate from it either all male or all female. It will be seen that not only do different cells for the different sexes develop themselves All evidence goes to support the view that such external influences as would favorably 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 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 I am at the same time unwilling to omit data, resting upon numbers which have been gathered from statistics, and are not without value for the determination of many important questions. Ploss has in this way shown that in favorable years, when food was cheap, the births showed an excess of girls. Under unfavorable circumstances, more male individuals were born. A comparison of statistics, however, soon led to another theory, which culminated in this result, that in all countries an excess of male individuals was born. To what extent this relation between the numbers of the sexes can be maintained, and may serve for a fixed rule, is at the same 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 They represent 59,350,000 births. These showed an excess of male births. The proportions were 106.3 boys to 100 girls. Of course, these numbers refer to the new-born, and must necessarily be very much altered by the age of puberty. In fact, the powerful influences which come into play in the life after birth would very considerably affect the former of the above numbers. This is, however, a matter for further statistical investigation, and of little importance in our present inquiry. The numbers (Oesterlen) are in this respect very remarkable: the average of the total number of births in the various states corresponds very nearly with the numbers in the several states, or at least shows no difference worthy of consideration. In the single states, the proportion of boys to 100 girls varied from 105.2 to 107.2. Thus the proportion of the number of male individuals I am prompted here to quote also the statistical numbers given in Hensen’s work, which have been taken from Darwin’s ‘Descent of Man.’ Of pigs, rabbits, and pigeons, more males are born than females. For every 100 mares, 99.4 horses are born. In the case of greyhounds, 110 dogs are born for every 100 bitches. Of horned cattle 94.4 males, of poultry 94.7 males are born for every 100 females. The degree of accuracy and the limits of error which here remain undefined, make fluctuations easily perceptible. The mistakes, also, which may be made in such cases, are not always the same. Statistics have been in many other ways called in to assist in the discussion of the 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 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 Bidder is in many respects inclined to give his assent to the theories of his predecessors, The evidence of Stieda, Berner, and Birelli, and especially that of Wilkens, respecting the domesticated mammals, leads, however, to this conclusion, that the theories respecting the relative proportions of male and female births set forth by Sadler and Hofacker must either be given up or their value considerably discounted. Specialists are also to be found who, in order to explain this theory, have availed themselves of Darwin’s law, and in a certain measure the results admit of this explanation. The older parent, who evidently under such normal circumstances as might be anticipated has a shorter time to live than the younger individual, his consort, naturally in the struggle for life, makes an effort for the preservation of his sex. Accordingly, the elderly husband of a young wife, or vice versÂ, the elderly wife of a young husband, will make an effort to preserve the sex which is first threatened with death, but which may at least be replaced by a majority of births. In so far as these theories are mere calculations and results which have originated from comparisons of numbers (the numbers themselves being in many cases of no practical value), the conclusions reached may appear to be astonishing, and may be used to support either one view or another, or to contradict 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 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 to 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 literature 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 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 has 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 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 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 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. 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 means 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 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 a 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 or 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 more 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 be 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 of 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 organs 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 exercise 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 bear 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 communicates 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 results 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, Then comes the theory of the allotment of the male and female in man, and in all the 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 right 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 previous 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 characteristics 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 it 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, 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 of 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 anomalous 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 many 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 to 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 appears In order to throw light on the causes determining sex, PflÜger (in connection with 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, PflÜger 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 that 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 regions 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 are 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 and 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, 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 develop 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 rutting 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, an 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 again 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. 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 with ArisÆma (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. I adduce this instance, for the sake of remarking respecting it, that on this subject also controversies exist, which must be settled by wider studies of the life of plants. Cornaz has tried to derive from cows evidence in support of Thury’s theory. He had twenty-nine cows impregnated with attention to the rutting time, and from twenty-nine births received twenty-two females and seven males. Cornaz attested his experiment by a declaration, and the experiment was repeated in the French state domains. But the experiment alone was striking enough to invite repetition. It also met with partial success. But the plan was afterwards entirely given up, perhaps in consequence of disappointments. In this case it very likely happened—as in such experiments it very easily may happen—that, in consequence of insufficient practical knowledge on the part of the experimenter, the actual commencement of the rutting time I here pass over a great number of proofs which Thury gives in his essay. Funcke (1866) made in his ‘Physiology’ the following remarks on Thury’s theory:—“Although the origin and determination of sex is not indisputably proved to depend upon the degree of ripeness of the ovum, it appears to me that we have not reached the right time for determining the factor upon which it does depend. These experiments have been made to repose upon a fact, which fact certainly proves, beyond the possibility of dispute, a relation between the fertilization of the ovum and the Thury’s theory can be very suitably brought into agreement with the theory of cross-heredity of sex, and explained by the assistance of that view. The cow, at the beginning of her rutting, is not in a condition of great sexual vigor. If the ovum be effectually fertilized, it may be supposed that the bull, in procreative activity the superior consort, will be fitted not to reproduce his own sex, but that of the weaker cow. At the end of the rutting period the cow, which is brought According to the theory of cross-heredity of sex, female creatures should in the former instance be produced, and in the latter males, which same result is reached in accordance with the theory of Thury. Attempts have been also made to apply Thury’s theory to the human species. The menstruation of women has been compared with the rutting of the lower animals, and has been considered a protracted, oft-repeated rutting. Now, as an ovum is specially developed every month, it follows that this ovum requires a certain part of a month to attain a more or less advanced degree of ripeness. According to this, the ova which are fertilized a short time after menstruation The mucous membrane of the womb ought, about ten days before the beginning of menstruation, to thicken itself distinctly in consequence of a turgescence and dilatation of the vessels. In consequence it appears swollen and loosened, and it has reached the culminating point of swelling when the menstruation is at its highest. After menstruation the swelling does not immediately decrease, but lasts on for about nine days, until the mucous membrane returns to its normal condition. (Hensen.) Thus it seems that the swelling and hyperÆmia in the womb appear at the same time as the conditions which lead to the ripening of the ovum. The fertilization of the human ovum would be, therefore, most efficacious at the time when the mucous membrane of the womb is also most appropriately Now, it may appear not to be a matter of indifference (and may very likely even have some connection with the development of sex) whether the ovum is fertilized at a period during which the mucous membrane is passing through its changes in order to reach its highest point of swelling, or at the time, when, after menstruation, the mucous membrane is, during so considerable a period (nine days), passing through a retrograde metamorphosis in order to return to its normal condition. This protracted process seems to correspond to the protracted rutting in the It is not sufficiently known to how great an extent the principles of Thury’s theory have hitherto found their right application to the case of man. They seem in practice to be applied in different ways. It seems that in cases where a result was obtained it could be more easily explained by the principles which have been already described under the theory of cross-heredity of sex. The assumption of a greater or lesser degree of ripeness of the ovum which was to be developed was a very questionable one. The different processes with which we have become, in more recent times, acquainted as symptoms of the ripening of the All the above symptoms occur alike in the ova destined for the male and for the female sex. That ripeness of the ovum upon which Thury’s theory insists, lies in the nature of the ovum apart from any anatomical signs. It is a condition of the ovum which we can only attempt to explain by laying down the principle that an ovum which has been for a longer time prepared in the female generative We have mentioned above that on the occasion of Thury’s experiment, the desired result was effected in twenty-nine cases. Pagenstecher, Siebold, and KÖll have dealt critically with Thury’s work. Coste was not in a position to confirm these experiments, nor to verify them. In order to test Thury’s results as applied to the human subject, SchrÖder obtained the assistance of young women, who were in a position to give him positive and accurate information respecting the time at which they became pregnant. The women could name the day on which they had had sexual intercourse, and knew the date of the last menses. From careful calculation of the interval between these dates, it was possible to ascertain approximately The experiments of Albini in Naples (according to Kronecker’s report ‘Centralblatt fÜr medicinische Wissenschaft,’ 1868), which he made during four years in his great poultry-yard showed in the first place that hens for eight days after being separated from the cock laid none but fertile eggs. On the ninth and tenth day the fertile and infertile Hens never yet impregnated, or such as had not been impregnated for at least a month, in three days (after impregnation) laid fertile eggs, which increased in number daily. According to Albini, hens can in Naples leave the eggs which they are hatching. The shell can be partly broken off and again replaced without the embryos necessarily perishing. But care must be taken that no fungoid growth reaches the germ, as this is easily fatal to it. Indeed, it has been recently shown that new-laid or well-preserved eggs are free from all micro-organisms. When these appear they have And now the result of Albini’s breeding experiments upon poultry with respect to the origin of sex. From three to six days after intercourse with the cock the hens lay eggs, from which on the average an equal number of males and females are developed. In the warmer part of the year the number of males appears to be greater. Better nourishment of parents seems also to exercise an influence over the sex of the young. Such eggs as were laid from ten to fifteen days after complete separation from the cock, gave when hatched generally a distinctly greater number of females. Albini found that the greater number of these died of anÆmia. He ascribed that to imperfect fertilization, and considered that development of an excessive number of females was to be ascribed to the same cause. Albini inclines towards the theory of Thury, in accordance with which the principal cause of the development of sex lies in the degree of ripeness of the ovum. He is opposed to the theory of Coste and Gerbe, which declares that the ova of the birds and mammals are fertilized when they fall from the ovary. The place where this took place was, according to their theory, exactly localized, at the opening of the Fallopian tube, and not at any place in the length of the tube. Fertilization in the Fallopian tube or uterus is allowed to be possible, and it is admitted that, in exceptional cases, fertilization of the hen’s egg is possible so long as it is not surrounded by the shell-membrane. This opinion, however, is in direct contradiction to that of Lenkart and Newport and many others, who hold that the albumen, which gathers around the yolk in the oviduct, hinders the penetration of the spermatozoa into the yolk. When Albini had collected his facts he came to the conclusion that, in the case of animals which bear many young, the last are mostly male, and explains this by the hypothesis that the ova passing through the Fallopian tube thrust the semen back, so that the ova which come behind are therefore fertilized in a more advanced stage. Meyer believes that he has incontestably proved against Ahlfeld that the sex is determined at conception. He does not appear to The longer the ovum exists free from the ovary, the longer it remains without the surrounding of those elements (contained in the ovary) which are necessary to it. Apparently, in consequence of the absence of these elements, it is all the time drawing nearer extinction, or it may at least become gradually less capable of maintaining its own sex—which is feminine. At least, it appears, before it is overtaken by the total extinction which threatens it if it is not fertilized, to lose the energy necessary, when fertilization H. A. Pagenstecher attempted an important readjustment of Thury’s theory, and tried to show that it might be made concordant with Pagenstecher remarks that the relations which have existed anterior to the fertilization of the ovum, as well as its age (with which its ripeness is connected), are from the outset without influence on sex. The embryonal germ, before its fertilization, is an embryo whose sexual development is undetermined. In this case fertilization acts as an external factor in the direction of determining the sexual quality of this indeterminate embryo. The act of impregnation would be of influence upon the sex of the embryo in accordance The experiments of Knight, who found that melons and cucumbers produce male blossoms under higher temperature and female under lower (which was verified by Mauz), demonstrate that, in this case, such external factors as warmth, light, dryness, have an influence upon sex. Pagenstecher, however, believes that the conditions of origin of sex are not the same in animals and plants. We must not, he says, from these observations draw conclusions off-hand respecting the sexual propagation of plants nor of animals in general. It must be further pointed out with regard to the thesis that ova which are emitted last have had more time to ripen, that we must reflect whether the process of ripening may not have also begun late. Thury’s observation that the last egg laid by a singing bird developed a male (communicated by O. Bourrit), and that in the case of hens the majority of the later eggs were males, seemed to Pagenstecher not quite certain. He mentions also a method by which, in poultry breeding, the breeding experiments can be conducted on a regular principle, which I shall quote word for word:— “For this experiment a number of hens are taken which may be anticipated to be “setters,” unless the use of incubators is preferred. The hens are to be separated, and the eggs which each one lays in her own particular nest are to be marked with numbers corresponding to the days on which they were laid. “The eggs of the different hens are now to be rearranged, so that the eggs which each particular hen is given to hatch shall, as nearly as possible, have the same numbers. For example, if the number of the hens be six, and the period of laying up to the time “In this way the doubt will be avoided, which necessarily arises, if I give the eggs of one hen, although marked, to be hatched by her alone. “In the latter case, it can very seldom be known with certainty from which egg-shell a cock or hen issued. “In this experiment, on the contrary, one can quietly wait until the cocks and hens in the growing broods of the different hens can be clearly distinguished and numbered, seeing that each brood has numbers (of the days of laying) of very nearly the same value. The experiment is easier and less subject to the possibility of error when the eggs belong to different varieties and are taken from known parents.” Fertilization in many cases alters the future sex as soon as it affects the germ in some corresponding manner. The germ develops itself, and, in the case of creatures whose ova develop without fertilization, evolves one, or the other, or both of the sexes. According to Pagenstecher, fertilization often alters the determination of the sex of the germs which attain to development in the ova. The point of time in the life of an ovum, at which it has reached that degree of ripeness which gives it such a character that the semen can no longer affect the determination of the sex, cannot be absolutely settled. A more powerful bull might beget female calves earlier in the late rutting time than an older one. After further explanations and critical expositions, which suggest themselves in the course of the examination of the theory, Pagenstecher lays stress upon the following important dicta of Thury’s teaching:— 1. Sex depends upon the ripeness of the ovum at the time of fertilization. 2. The ovum which, at the moment of fertilization, has not yet reached a certain degree of ripeness, produces a female. If this degree of ripeness has been passed, the ovum, upon fertilization, produces a male. 3. If at the time of rutting a single ovum is detached from the ovary, and descends slowly through the genital canal (animals which bear a single offspring), fertilization taking place at the beginning of the rutting suffices to produce a female, and at the end of the rutting to produce a male, provided that the change in the condition of the ovum takes place normally during its passage through the genital canal. Both the theory as Thury stated it, and the critical remarks that have been made upon it, have been further elucidated in many subsequent works. Here Pictet, Chavannes, C. Vogt, De Philippi, and others, have taken The facts which stand in certain relations with the fundamental laws are numerous, and the manner in which they tend to affect those fundamental laws occasions various combinations in the variety of phenomena. For the animal kingdom Thury adduces a number of observations as the foundation of his teaching. We shall here turn our attention to some of them. We have already pointed out that in the case of the eggs of the singing birds, which are laid by turns, the young which emerges from the last strikingly smaller egg, the so-called “nest egg,” is always a male. According to the theory of Thury, the ripeness of the ovum depends also upon the place which, in the animals, it occupies in the ovary. In consequence, according to this If the activity of the generative apparatus of the female should be increased by any circumstance, in the case of the animals the ripening of the ovum would be accelerated. The consequence would be an earlier detachment or emptying out of the ova from the ovary. In consequence, the generative operations in the animal are of a more complex nature than in plants, a fact which is of great significance for the determination of sex. The continuous intercourse of the male with the female increases the capacity for accelerating the ripening of the ovum. According to Burdach the mother animals who do not have frequent intercourse with the male bear more females, because their ova do not, before fertilization, attain so high a degree of ripeness as to be able to develop into males. Also, it appears from observations on Amongst cattle and sheep the first-born are more often females. (Girou.) Also in the human species a greater number of females are observed amongst the first-born. Here, on the one hand, regular intercourse with the male is to some extent unfamiliar; whilst, also, according to Thury, the choice of the date of marriage might be of importance. The constancy of the births may be explained by the From illegitimate births more girls result than from marriage. The reason of this might be sought in the influence of the active excitement of the female at the time at which the conception took place, that is, shortly after menstruation, when the woman is most easily excitable. The various theories respecting the explanation of the production of sex which are known to us, from the earliest accounts down to the modern predominance of natural philosophy, have been collected by W. His. (‘Archiv fÜr Anthropologie,’ Band 4, 5.) Since then, it is true, during the course of successive studies, and more especially of those which have been made during the present century, many substantial alterations have appeared in the views held respecting the Thus, discoveries have been made which have exercised a very wide influence, for example, that of the ovum in man and in the other mammalia (Baer, 1828), or the penetration of the spermatozoa into the protoplasm of the ovum as a necessary condition of fertilization. In later times it has been made certain that the head of the spermatozoon is a nucleus, and that only one spermatozoon penetrates into the interior of the ovum. Afterwards its head as a nucleus unites with a nucleus-part of the ovum, forming a new nucleus in the ovule, which, together with the surrounding protoplasm, serves as the point of departure of the further processes of development, and in this condition is described as an oosperm. After this follow other extensive details of the process of development, which will not be described here. It may be already seen, The doctrines of the physiology of metabolism in men and beasts under different But, before entering upon the fundamental principles of the theory which I have set forth, I wish to mention a treatise of Mayrhofer’s, the principal results of which I shall briefly recapitulate. After that I shall mention briefly such information as I have met with respecting the nutrition of the mother. Mayrhofer was led by critical notices and the observations of others, and, further, by his own experiences, to conclusions which he set forth in propositions, some of which I select here. In the plants and the lower animals food Whether sex in the human species is determined at conception, or only develops itself afterwards, we must attempt to discover from obstetric experience. The twins and triplets contained by one chorion are of the same sex, and have a common placenta in which the blood passages of both umbilical cords communicate with one another. On this account, also, many opine that the identity of sex is occasioned by the intermixture of the blood, an opinion regarded, on the contrary, by others, with incredulity, because the intermixture of the blood might very possibly lead merely to a mixture and Heartless monstrosities (Acardiaci) are, in spite of imperfect nutrition (the conditions of proper nutrition by the blood are wanting in the embryo), of the same sex as normal offspring. Now, cases of this kind demonstrate that, in the later periods of development, although the conditions of nutrition are not alike, nevertheless the similarity of sex in the twins is maintained; so the foundation of the future sex would be laid at the period of conception. This rule which proves valid for the twins found in a single chorion, would apply for all human ova in general, because According to Mayrhofer, placentÆ are rare in which, where there are two chorions, communication is found between the vessels of the two umbilical cords. In addition to what has been already mentioned, Mayrhofer lays down the law, which we find frequently stated in many quarters, that the older of the two parents has a greater preponderance in favor of the propagation of his, or her, sex. Especially the physical maturity on the man’s side enables him to propagate his own sex, either in connection with younger or older women. A superiority on the part of the woman produces girls. Our author only partly supports Thury’s theory, and considers it an open question whether the time of impregnation has any influence on the origin of sex. But he lays down this principle, that an economy of the semen by infrequent indulgence in It may be possible to obtain more exact data respecting the origin of sex from the artificial breeding of fish. In this case the properties of the sperm, as well as of the ova, might be observed at an earlier date by means of a fertilization effected externally. Attention might be also paid to the age of the parents. In short, all the factors of artificial influence upon the development of sex can in this case be taken in hand and controlled by varying the process of artificial fertilization. The author does not appear to know that the results obtained by artificial breeding differ remarkably from those which are the consequence of the natural multiplication of fish, nor that the development of sex is unfavorably affected in many ways. The cause of that lies very likely in the nutrition of the young fry, and perhaps, also, partly in cross-breeding. What influence the physical welfare of the parents, and especially of the mother, has on the sex of the offspring in man, besides other factors deserving of attention, ought to be discoverable from the statistics of the lying-in hospitals. This is, in my opinion, hardly to be expected. On various occasions, whilst taking into consideration the possibility of an influence on the part of the parents over the sex of the child (in such respects as have been placed before us in the literature dealing with this subject), we often had occasion to direct attention to the food of the parents. And especially the food of the mother seemed to us to be of the highest importance. Now, it is universally known that metabolism is increased during pregnancy. The products of excretion in the case of pregnant women are much smaller than the quantity of matter taken in, in the shape of food. During pregnancy the number of blood corpuscles suffers an observable diminution. Still plainer is the reduction of the quantity of hÆmoglobin, when measured with Fleischl’s hÆmatometer. This last phenomenon is very Observations of setting hens are not without interest. In their case, also, a diminution of hÆmoglobin is observable during the period of incubation. The hÆmoglobin can sink to nearly 50 per cent. of the normal amount. With the increase of hÆmoglobin in the embryo and its simultaneous diminution in the mother during incubation, it happens, at a certain period in the process of development, that the embryo in the egg and the setting hen possess a nearly equal measure of hÆmoglobin with a nearly equal number of blood corpuscles. An increase of the quantity of hÆmoglobin until the normal amount is reached may be observed in both towards the end of incubation. The Rhine salmon each year go up in a well-nourished condition from the sea into the fresh-water streams to spawn. There Many have paid particular attention to the nourishment of the maternal organism. Investigations have also been published dealing with the nutrition of the parent animals in cases when it was desired to exercise an influence over the sex. In fact, we have frequently touched upon such subjects, although only lightly. Here, as we are about to proceed to the subjects of nutrition and metabolism in the human female awaiting impregnation, we find ourselves compelled to acquaint the reader with a number of facts which permit us to assume a connection between the food supply (including metabolism) and the development of sex. |
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