II. THE SEXUAL EPOCH OF THE MENACME. (continued 7)

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

The circumstance again (likewise alluded to above), that in the case of illegitimate births almost always the excess of male births is less marked than in the case of the offspring of legal unions, is regarded by Ploss as offering further proof of the influence of 435nutritive conditions upon the determination of sex. Illegitimate mothers are on the average women at the very best age for child-bearing, women who have worked vigorously, are themselves well nourished, and are therefore better able to nourish their unborn offspring than (on the average) married women. Further, it is a remarkable fact that in Saxony, regions of which the elevation above the sea-level is less than 1,000 feet, produce comparatively more girls than regions at an altitude of 1,000 to 2,000 feet above the sea. This Ploss refers to the worse nutrition of the women living at the higher altitude, for the fact is well known that the higher we go above the sea the less fertile is the soil and the more limited is its produce.

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

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

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

436Breslau (“The Causes of the Determination of Sex”) offers in the first place theoretical objections to the view that nutritive conditions in the mother are determinative in the production of the sex of the offspring; and he then proceeds to quote statistical data which are opposed to any such theory. He rightly insists, in the first place, that, inasmuch as it is unquestionable that in the act of fertilization the spermatozoon induces in the ovum certain changes, the effect of which is manifested in days far later than those of intra-uterine life, by the production of the most manifold and various somatic and psychical resemblances to the father, it is obvious that this single occurrence of the fusion of the spermatozoon, the bearer of the paternal influences, with the ovum is competent to induce in the ovum a molecular arrangement upon which the determination of sex may be supposed to depend—it is not necessary to suppose that for this determination, repeated actions, or a prolonged period of time, is requisite.

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

The paternal influence in the determination of sex is regarded by Breslau as likely to be at least as important as that exercised by the mother. Unquestionably the semen is subject to certain variations in quality and in quantity, and it is possible that these variations may make themselves felt in the subsequent development of the embryo. Of the semen, as of all secretions, we can assume with some probability that in certain conditions (conditions which are, indeed, but little understood), it may exhibit a greater or less intensity in its stimulating qualities, and that in this way it may be subject to changes, according to which it will tend to influence the development of the embryo, now in the female, and now in the male direction. Again, in view of the continued interchange of nutritive materials between the embryo and the maternal organism, 437it is probable enough that the constitution of the maternal organism and likewise that of the ovum, at the moment of fertilization, are not matters of indifference to the determination of sex. But to attribute to the nutritive condition of the maternal organism the sole or even the principal influence in the determination of the sex is an unjustifiable assumption.

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

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

Wappaeus contests the conclusions of Ploss even more vigorously, and adduces the statistics of Sweden in the 20–year period 1770 to 1790, in which period this kingdom repeatedly suffered from 438famine in consequence of failure of the crops, so that the births and deaths were largely affected. It appeared, however, that the more abundant or more scanty nutrition of the inhabitants of Sweden during this period had no marked influence upon the sexual ratio.

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

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

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

It is obvious that the statistical data at present available regarding the sexual ratio in the case of multiple births are far too variable for it to be possible to base upon them any valid conclusions as to the influence of the nutritive condition of the mother upon the determination of the sex of the offspring. And taken as a 439whole the statistical data hitherto available do not enable us to infer with confidence that nutritive conditions, and more especially the nutritive state of the maternal organism, exercise any effect upon the determination of the sex of the offspring.

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

The Jews, more especially, whose religious ordinances forbid them to have sexual intercourse either during or shortly after menstruation, and among whom there is a great excess of male births, have been adduced as a proof of the thesis that sexual intercourse 440during the later part of the intermenstrual interval tends to favour the procreation of boys. In Leviticus xv. 19, we read: “And if a woman have an issue, and her issue in her flesh be blood, she shall be put apart seven days.” From the commentary in the Talmud it appears that these seven days are to be reckoned from the commencement of the flow. Statistical reports from various countries show that among the Jews there is a greater excess of male births than among the other inhabitants of the respective countries. The overplus of male births exhibited by the Jews varies from 1 to 15%, the difference probably depending on the fact that the number of instances under consideration is too small for uniform results to be possible. In Prussia, during the period 1820 to 1834, the sexual ratio among the Jewish births was 111 : 100; during the period 1849 to 1852 it was 106 : 100; in Hungary during the period 1835 to 1855 it was 117.1 : 100; in Sweden, 1851 to 1855, it was 108 : 100. Among illegitimate children of the Jewish community the sexual ratio was, in Austria, 123.9, in Prussia, 118.6.

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

441

Number of Days Between Reputed End of Menstruation and Reputed Occurrence of Conception. Number of boys born. Number of girls born. Boys and girls together.

1 7 1 8

2 6 3 9

3 9 5 14

4 15 3 18

5 3 6 9

6 5 6 11

7 6 5 11

8 2 8 10

9 4 5 9

10 6 4 10

11 6 5 11

12 3 6 9

13 4 5 9

14 6 5 13

15 1 2 3

16 2 5 7

17 2 3 5

18 3 3

19 1 3 4

20 1 2 2

21 1 1 2

22 4 1 5

23 1 1

24 1 1

25 2 2

26 2 2

27 1 1

28 1 1 2

31 1 1

102 91 193

Baust gives a report, based, he says, upon “thoroughly trustworthy data,” furnished by personal friends, regarding 14 cases, which show, in his opinion, that every conception occurring in a week after the cessation of the menstrual flow leads to the birth of a girl; but that when conception occurs on the fifth or sixth day after menstruation the result varies as regard sex. Swift, from a report of 20 cases, draws the conclusion that in the intermenstrual interval, boys, in the latter part of the interval girls are conceived.

The influence of the strength of menstruation upon the determination of sex has also been studied by the statistical method, starting with the idea that menstruation, in proportion to its strength, affords on the average a measure for the subsequent nutrition of the embryo, and this nutrition is further supposed to determine the 442sex. Düsing therefore arranged the births occurring in the lying-in hospitals of Dresden, Leipzig and Jena, according to the information given regarding menstruation in the clinical history of each case; it appeared that when menstruation was comparatively scanty, there was a greater excess of boys than when menstruation was comparatively abundant. The actual figures were the following:

Abundant menstruation. Scanty menstruation.

Dresden 902 847 495 431

Jena 66 69 56 45

Leipzig 21 22 239 211

Totals 989 938 790 687

Sexual ratio 105.4 114.7

Here also we may append the figures obtained by Düsing regarding the births of foals at the Prussian stud-farms, which he regards as supporting his view that by natural selection all animals have acquired the faculty, whenever stronger demands are made upon their sexual capacity, of procreating a larger number of individuals of their own sex. In the tables we learn how many mares on an average a stallion had covered in each year, that is, we learn how great were the demands made upon the sexual capacity of the stallion in that particular breeding stable in that year. The figures relating to the years 1859 to 1892 were tabulated and averages were drawn with the following results:

Number of Mares Served. Number of Foals Born. Sexual ratio.

Colts. Fillies.

60–70 42,445 41,933 101.22

55–59 56,511 66,226 100.49

50–54 59,940 61,096 98.18

45–49 57,077 59,216 96.39

40–44 59,967 62,007 96.71

35–39 38,348 40,181 95.44

20–34 26,354 27,069 97.35

443From these figures, which relate a very large number of instances indeed, we learn that when greater demands are made upon the stallion, more males are procreated. In fact, except for two slight divergencies, the rise in the sexual ratio proceeds strictly pari passu with the increase in the number of mares covered.

I must, however, draw attention to the fact that this assumption when applied to the human species, that the man on whom whose sexual capacity especially extensive demands are made, procreates an especially large number of male children, is not confirmed by the sexual ratio among the offspring of polygamous marriages in which unquestionably greater demands are made upon the husband’s sexual powers than is the case in monogamic unions.

The reports of travellers of earlier days, to the effect that in Oriental countries more girls are born than boys, have recently been confirmed by several observers. Campbell states that in the harems of Siam the number of boys and girls born is equal. Clarke states that among the Mohammedan Indians more girls are born than boys. According to McLennan Indian experience teaches us that where polyandry prevails male offspring predominate in numbers; but where polygamy prevails there is, on the contrary, an excess of female infants. The following data collected by Goehlert from historical reports and from genealogical writings, regarding the progeny of notable persons living in polygamous unions, show certainly a large excess of female offspring over male:

Children. Sexual ratio.

Male. Female.

Morocco: Muley Scherif 24 124 19.4

Palestine: Rehoboam, King of the Jews 28 60 46.6

Arabia: Imon of Sana 14 74 18.9

Turkey: nine sultans 110 128 85.9

According to Tousenel, love marriages give rise to more daughters than sons, whereas among the offspring of conventional or compulsory marriages, male children predominate. Further, among the offspring of legitimate unions, the excess of males is greater than among the offspring of illegitimate unions. A physician, V. J. Cook, maintains that boys are procreated in the evenings (before 444midnight), but girls during the early morning hours—at which latter time women are less “impressionable” than during the evening hours.

Düsing, starting from the common belief that all animals have the faculty, when there is a lack of individuals of one sex, of procreating an excess of offspring of the sex which is deficient and thus of restoring the balance between the sexes, maintains that numerous factors, through the co-operation of which the sexual ratio is regulated, act in temporal succession. He shows that the individuality of the mother has an influence upon the sex. But this finds expression through the qualitative constitution of the ovum; hence already before fertilization there must exist a tendency toward the development of one sex or the other—for example, younger ova tend to become females; older ova, on the contrary, to become males. It has further been shown that the individuality of the father, that is to say, the qualitative constitution of the sperm, has an influence in the determination of sex. Thus, by means of the influence of the sperm, the already-mentioned pre-existing tendency of the ovum can in some instances be counteracted and overpowered. The influences in the personality of the father and of the mother, which during fertilization find expression in the qualitative constitution of the sperm and of the ovum, respectively, can thus bring about a resultant tendency, acting in one direction or the other with varying force. Thus, after fertilization, we have this resultant tendency toward the formation of a male or female embryo.

But, Düsing continues, at this time the sex is not definitely determined. The influence of the nutritive condition in which the fertilized ovum finds itself has yet to make itself felt. This influence on the determination of sex through the maternal nutrition, continues (in the human embryo) for as long as three months, but even when the reproductive organs of the embryo have definitely begun to diverge in the direction of the masculine or the feminine type, as the case may be, some nutritive influence, if it is sufficiently powerful, may yet turn the balance in the other direction, so that a partial or complete hermaphrodite results, a being uniting the characteristics of both sexes.

Actual inheritance of sex, of which people used to speak, cannot, in Düsing’s opinion, possibly occur. The mode in which one sex or the other develops is indeed inherited; but the decision which sex shall develop does not depend upon inheritance, but is determined 445by the co-operation of several outward influences. The qualities by which this is effected are acquired by adaptation to general or special vital conditions.

Wilckens (“A study of the Sexual Ratio and of the Causes of the Determination of Sex in Domestic Animals”) opposes the views of Düsing, on account of the results of his own investigations, relating to the births of 30,000 domestic animals. He formed the following conclusions:

1. Locality (soil and climate) has an influence upon the sexual ratio and upon the determination of sex in domestic animals, but this influence is probably indirect only, being exerted through the intermediation of the nutrition of the embryo in utero.

2. The season in which the domestic animal is conceived affects the sex; the hot season favours the production of males, the cold season that of females; in the hot season, in general, the appetite and nutrition of domestic animals diminish, whereas in the cold season these increase.

3. Regarding the male progenitor, neither his age, nor his sexual energy, nor the demand made upon that energy, nor the age of the semen, has any influence upon the sexual ratio or the determination of the sex of the offspring.

4. The age of the female progenitor influences the sexual ratio and the determination of the sex of the offspring in this way, that in general, primiparæ and young mothers conceive a larger number of female offspring. This influence of age may be referred to the fact that in general young mothers nourish their offspring in utero better than older mothers.

5. The nutrition of the fruit in utero influences the determination of sex, speaking generally, in the following way, that better nutrition favours the determination of the female sex, worse nutrition favours the determination of the male sex.

6. In addition to the influence of nutrition of the fruit upon the determination of sex, other influences, whose nature still remains obscure, must also co-operate, because one and the same progenitor in similar nutritive conditions does not always procreate offspring of the same sex.

7. Owing to the operation of these unknown influences, prediction of the sex of the offspring, and voluntary determination of the sex of the offspring, remain impossible. All we can say is that there is some probability that young and well-nourished mothers will procreate a comparatively larger number of female offspring, 446whilst elderly and ill-nourished mothers will procreate a comparatively larger number of male offspring.

II. Anatomical Investigations.

Of anatomical investigations and discoveries, those more especially relating to the sex-relationships of twins and triplets have been applied to the elucidation of the problem of the determination of sex.

The first and most important fact in this connection, one that is not merely a rule confirmed again and again by anatomists and gynecologists, but is further, as Mayrhofer has demonstrated as a result of his researches in von Braun’s clinic, a “natural law,” is this, that twins and triplets enclosed in a common chorion are invariably of the same sex. The sex-identity of such twins has been referred to the similarity of their nutritive conditions (Leuckart, Ploss), and more especially to the communication between their bloodvessels; and an intimate connection between these relationships and the determination of sex has been believed to exist.

Mayrhofer, however, opposes this assumption by the following deductions (“The Determination of Sex in the Human Species”); “Fœtuses enclosed within a single chorion always possess a common placenta, in which the blood-channels from both umbilical cords frequently, in the case of twins perhaps invariably, communicate. It might therefore be supposed that the sex-identity of embryos enclosed within a single chorion is due to the intermixture of their blood in the placenta. Hyrtl, however, describes a triplet’s placenta, in which, though all three fœtuses were enclosed within a single chorion, the vessels passing to the umbilical cord of one of the fœtuses were entirely distinct from the vascular area common to the two other fœtuses; it is therefore probable that in the case also of twins enclosed within a single chorion there is not necessarily any communication between their bloodvessels in the common placenta. But even if it were proved that in the case of twins enclosed within a single chorion their bloodvessels always do communicate in the common placenta, we could not therefore infer that the intermixture of the blood of the two fœtuses is the cause of their sexual identity.

“For the intermixture of the blood of the two fœtuses in the common placenta could never lead to a complete identity in the composition of the blood of the two; it could only lead to a diminution 447of the differences which would exist between the bloods if their placental circulations were entirely distinct, and the similarity in the bloods thus established could not be expected to do more than make it a general rule that such twins or triplets should be of the same sex; but to this rule exceptions might be expected to occur in certain cases, as when hæmatopoiesis in the two (or three) fœtuses was very different, or when the circulation through the intercommunicating bloodvessels was interfered with through the pressure of fibrinous deposits—differences between the bloods would then arise sufficient to cause differences in sex (if identical composition of the bloods is presumed to be the cause of the sexual identity).

“Experience teaches us that the existence of communicating vessels in the placenta does not suffice to induce a close similarity of growth and of the formation of the organs in twin fœtuses; nor does it prevent the illness and death of one fœtus leaving the health of the other undisturbed, although the communicating channels remain open; so that, if we except acardiac monsters, it is correct to say that each fœtus pursues a secluded life, uninfluenced by the life of its neighbour. Acardiac monsters, on the other hand, always receive blood which has already served for the nutrition of the normal fœtus, and the result of this is an arrested development and a striking preponderance of connective tissue in the acardiac twin. But notwithstanding the fact that the failure of its own proper circulation (which is indeed rendered possible by the existence of the communicating vessels in the placenta) leads to its defective nutrition with a blood inferior to that supplied to the normal fœtus, the acardiac monster is always of the same sex as the normal twin.”

From these considerations Mayrhofer rightly infers that the identity of sex of two fœtuses contained in a single chorion, since it does not depend upon the existence of communicating vessels in the placenta, must arise from a developmental tendency already existing in the two germs at the time of conception—or, in other words, that at the time of conception their sex is already inalterably determined.

This conclusion with respect to the sex of twins contained in a single chorion may very readily be extended to the inference that in the case of all human fœtuses the sex is already determined at the time of conception.

Another anatomical fact is that many twins are contained in a 448single chorion for this reason, that they originate from two germinal vesicles within a single ovum. It is an open question whether it is not possible for two embryos contained in separate chorions to come to lie in a single chorion through atrophy of the intermediate wall. If this is indeed possible, the invariable identity of sex in the case of fœtuses lying in a single chorion must lead us to agree with Mayrhofer in inferring that two ova lying within a single follicle, simultaneously fertilized, give rise to embryos of identical sex.

B. S. Schultze and Ahlfeld, as a result of the investigations regarding twins, also came to the conclusion that the sexual identity of twins depends upon their derivation from a single ovum. If, in accordance with what has been said above, an explanation of the sexual identity of certain twins is to be found in the fact that for such twins there has been a single conception only, and hence the influence, whatever it may be, by which sex is determined acts on both germs at the same time—still the sexual identity of twins in general is remarkable and has not yet been fully explained. The sexual identity in fact occurs much more frequently than appears to correspond to the percentage of twins derived from a single ovum. Von Fricks examined the data relating to multiple births in Prussia during the period of 1826 to 1879 and compiled the following table:

Per Cent. Twins. Triplets. Quadruplets. Quintuplets.

Boys only 32.6 24.5 14.3 33.3

Girls only 30.3 22.5 19.4

Boys and girls 37.1 53.0 66.3 66.7

2 B. 1 G. 28.5

1 B. 2 G. 24.5

2 B. 2 G. 23.4

3 B. 1 G. 19.5

1 B. 3 G. 23.4

4 B. 1 G. 33.3

3 B. 2 G. 33.3

According to Ahlfeld, of twin births in general, the ratio of those with a common chorion to those with separate chorions is 1 : 8.15. If, however, we wished to explain the frequency with which twins 449are of identical sex from the occurrence of such twins derived from a single ovum, we should expect to find a very different ratio, namely, 1 : 3.84; that is to say, twins with a common chorion would have to be nearly three times as common as they actually are. From these facts Düsing endeavours to draw the conclusion that external conditions have an influence upon the determination of sex, for very many external conditions are identical in the case of twins; as, for instance, the age of the father, the age of the mother, the nutritive conditions of the ova and of the spermatozoa, the nutrition of the embryo, etc.—all of these would influence both the twins in the same direction. A difference in the sex of twins, on the other hand, might be due to two successive fertilizations.

B. S. Schultze has been led by his embryological studies to the conclusion that there are male and female ova. Thus he believes that sexually identical twins originate from a single ovum with two germinal vesicles, thus assuming that a double fertilization of such ova is possible. But since in such cases the sexes of the resulting twins are always identical the spermatozoon can have no influence upon the determination of sex, but the conditions leading to the development of one sex or the other must pre-exist in the ovum—i. e., there must be male and female ova.

That as a matter of actual fact in some cases the female progenitor exercises an overwhelming influence on the determination of sex, and that the opinion held by so many that this determination depends upon the mother alone is sometimes supported by facts, is shown by the incident recorded by Darwin (“Descent of Man,” Vol. I.), that an Arab mare was delivered seven times successively of a filly, never of a colt, although she was covered by seven different stallions. On the other hand, the circumstance, if it is not to be attributed to pure chance, can also be explained by the constitutional vigour of this mare (Hensen) without adopting the above hypothesis.

Recently Upjohn has maintained that there are two kinds of spermatozoa, male and female; the latter are the commonest, but the former are the more energetic.

An interesting anatomical fact bearing upon this question has been discovered by M. Nussbaum, namely, that in ascaris megalocephala the reproductive glands are indicated already before the separation of the germinal layers; and Nussbaum suggests that this is also the case in all animals, although the proof cannot be obtained in every instance.

450Semper has shown also in the case of some of the plagiostomata that long before the beginning of the definitive development of the reproductive organs, the apparently hermaphrodite embryo already possesses at least the tendency toward the constitution of one sex or the other. For in these animals, at a time so early that as yet the reproductive glands exhibit no sexual differentiation whatever, the sexes can nevertheless be distinguished by what appears to be a secondary sexual character. In the female, namely, one ovary only is developed; and very early indeed in the embryos destined to become females we can observe an asymmetrical development of the two germinal furrows. By this characteristic the two sexes can be distinguished far earlier than it is possible to do so by the recognition of a histological differentiation of the reproductive glands.

According to Mayrhofer the prepotency of the male gives rise to the procreation of an excess of males in this way, that physical prosperity of the male probably leads to the generation of boys, whereas prosperity of the female tends to give rise to the generation of girls. Moreover, economizing of the semen by infrequent sexual intercourse tends to originate offspring of the male sex. In this connection Hensen remarks, apropos of the greater excess of male offspring among the Jews: “We might ask whether, in consequence of the comparative sexual continence of the Jews which demands a definite power of endurance on the part of the ova, there may not be effected a certain selection of the ova; and thus we may perhaps explain how it is that in this race an exceptional vigour is somewhat more often to be observed than in other races.” Bock assumes that “thinner semen,” such as results from more frequent sexual intercourse, favours the procreation of the female sex, whereas when intercourse is less frequent a larger number of boys is likely to be born. Janke indicates as two important fundamental principles of scientific physiology that, (1) sexual intercourse represents as it were a contest between the two parties to the sexual act as to which shall transmit his or her sexual influence to the child, the victor in the contest determining the sex of the offspring, and (2) that a crossed inheritance occurs, inasmuch as whichever progenitor proves stronger in this contest transmits to the child the sex other than his or her own. He therefore advises women who long to have a boy to drink a glass of champagne before fulfilling their conjugal duties in order to gain increased sexual vigour.

Fiquet also expresses the opinion that when a vigorous, passionate, 451and sanguine male progenitor has intercourse with a frigid and phlegmatic woman there will be a preponderant tendency for the offspring to be female; whereas, when the conditions are the opposite of these, the male progenitor being phlegmatic and cold, the female on the contrary sanguine, passionate, and ardent, the offspring will probably be of the male sex.

In opposition to these opinions of Fiquet and Janke, to the effect that the temperament and the sexual vigour of the progenitors have a determining influence in the origination of the sex of the offspring, Düsing insists that the quality of the reproductive products are alone influential. Düsing lays down the following proposition: “The greater the scarcity of individuals of one sex is, the more extensive consequently the demands made upon the sexual capacities of the individuals of that sex, the more rapidly their reproductive products are employed; and the younger these products therefore are when employed the more individuals of their own sex will appear among the offspring.”

Richarz believes, on the contrary, that the prepotency of the male gives rise to the procreation of more girls; a mother of high reproductive capacity will have more boys, one of less reproductive capacity, on the other hand, more girls.

Starkweather (“The Law of Sex,” London, 1883) states his view in the proposition: “The superior parent produces the opposite sex;” and he holds the quaint view that this superiority is displayed in certain anatomical characters of the face of the progenitor. He endeavours from the shape of the head and from the facial expression to deduce the superiority of the male and the female progenitor respectively. A high, square forehead, with prominent supra-ciliary ridges, constitutes, according to Starkweather, one of the principal symptoms of this superiority; important also are a strongly developed middle third to the nose, narrow lips, etc. He declares that in families known to him the possession of this Roman nose in the father is signalized by the possession also of a large number of daughters, while a Roman-nosed mother has many sons. The more the parents’ noses resemble each other the more equal will be the distribution of the sexes among the offspring. He connects this fact (!) also with the fact that the possessor of the aquiline nose is the ruler of the family. Men of great strength of character procreate chiefly daughters; women, on the other hand, with a powerful character and a firm will bring into the world a notable excess of boys. In the Southern States of the American 452union Starkweather found confirmation of his theory, since he observed there that among the offspring of white fathers and coloured mothers there was an excess of girls amounting to 12 to 15 per cent. Among the half-castes of Java, the so-called Lipplapps, in the third generation girls only are born, and these are sterile. The excess of girls in these cases depends upon the superiority of the white father; this superiority is transmitted to the few sons of the second generation, and these therefore procreate girls only to constitute the third generation; the latter are not powerful enough to bear children at all.

Roth has revived the old view that one ovary provides the germs for the male offspring, the other those for the female offspring. He believes further that in the process of cohabitation the mechanical impressions and stimuli received by one-half of the external genital organs, reinforced by contact with and pulling on the pubic hair, are transmitted through the pudic nerve and the hypogastric plexus to the corresponding half of the vagina and the uterus, to the Fallopian tube of that side and to the corresponding ovary. If, now, we can consider it as established (?), that in the human female one ovary discharges male ova only and the other female ova only, it seems to him that it is the corresponding half of the external genital organs, when specifically stimulated in sexual intercourse, and the consequently increased vital activity in the pudic nerve and its connections with the hypogastric plexus, that must be regarded as the organ by means of which sex is determined. Roth has also been informed by laymen that when for some time they have procreated daughters only they subsequently procreated sons, “when, having been accustomed to sleep on one side of their wife, they adopted the practice of sleeping on the other.”

Ricardi reports that in Modena the peasants say that a man whose wife has hitherto had daughters only, must, if he wishes to have a son, assume some other posture than usual in the performance of coitus.

III. Experimental Investigations.

A considerable number of years ago, Thury attacked the problem of the determination of sex by the experimental method. In his series of experiments he ascertained, using 29 cows, that in the case of 22 of these, which were served early in their heat, the calves were without exception heifers, while in the case of the remaining 7, which were served late in their heat, the calves were equally 453without exception bull-calves (Thury, “The Law of the Determination of the Sexes,” Leipzig, 1863); in the record of these experiments no mention is made of the age of the cows. Thury concluded that the sex was determined according to the fertilization of the ovum soon or late after its liberation from the ovary; namely, that an ovum fertilized soon after its discharge produced a female, whilst an ovum which had become comparatively old before it was fertilized became a male.

Thury’s sensational experiments gave rise to a succession of similar experiments, made mostly by cattle-breeders, above all in agricultural colleges and in stud-farms.

Some of these experiments were made in the agricultural colleges at Proskau and Eldera. The cows, which according to Thury’s views should have been delivered of heifers, were served as soon as their heat was observed (the heat lasted as a rule from 24 to 30 hours); these were delivered of 5 heifers and 5 bull-calves (in Proskau) and of 3 heifers and 5 bull-calves (in Eldera); the sexual ratio in these cases was therefore normal. On the other hand, cows which were not served until their heat had lasted for 20 hours were delivered (in Proskau) of 1 heifer and 4 bull-calves.

Further experiments (in Waldau) gave the result that cows served early were delivered of 1 heifer and 1 bull-calf. In another series (in Eldera) 9 cows served as soon as heat was observed (or, speaking strictly, in from ½ to 1½ hours of this), gave birth to 7 heifers and 2 bull-calves.

Experiments made at the Royal Friedrich Wilhelm Stud-Farm gave the following results: In the case of 20 mares, which if Thury’s theory had been correct should all have given birth to fillies, 11 only fulfilled this expectation; but 10, on the other hand, were colts. Touchon, in his experiments at Hohenhau, obtained 11 calves and 2 foals, exhibiting the sex expected in accordance with Thury’s theory.

Düsing made a compilation of the figures given in all the experiments made to test Thury’s theory, with the following results: Cows fertilized early were delivered of 13 bull-calves and 29 heifers; mares fertilized early were delivered of 10 colts and 13 fillies; cows fertilized late were delivered of 5 bull-calves and 2 heifers.

Gerbe made experiments on rabbits, putting the buck to some doe-rabbits soon after the beginning of their heat, but to others as late as possible in their heat. On examining the young in the horns of the uterus, from the ovary downward, the distribution of the sexes was found to be approximately equal.

454Whilst Coste’s experiments on a hen gave results contradictory to Thury’s theory, Albini’s experiments, made also on the common fowl, gave results in agreement with that theory. He found that the hens began again to lay fertilized eggs 3 to 6 days after intercourse with the cock (from which they had previously been kept separate); on the average, the distribution of the sexes in the chickens hatched from these eggs was approximately equal, with, however, a slight preponderance of cock birds. On the ninth and tenth days after separation from the cock the eggs laid were half fertilized and half unfertilized; on the twelfth day after separation from the cock the unfertilized eggs were in a great majority; but even as late as the eighteenth day after separation some of the eggs laid were still fertilized. The fertilized eggs laid from the tenth to the fifteenth day after separation when incubated produced a great preponderance of hen birds.

We have to thank breeders for a large number of experiments, such as those made by the breeder Fiquet, at Houston in Texas, who found that a bull upon whose sexual capacities excessive demands were made, procreated bull-calves exclusively; whereas in herds containing numerous bulls there were found among the calves born a preponderance of heifers. In thirty experiments on cattle Fiquet always found that the larger the number of cows a bull had to serve, and the longer they were kept in service, the larger was the proportion of bull-calves among their offspring. On the other hand, if certain cows had their sexual desires first satisfied by a gelded animal and were then served by a vigorous and lusty bull, an excessive proportion of heifers was born to these animals.

Janke obtained similar results in the breeding of sheep. In a report made to Düsing he states that in the early part of the lambing season more ewe-lambs are born than rams; in the latter part of the lambing season, on the contrary, more rams than ewes. The explanation he gives is that at the commencement of the pairing the rams are fresh and lusty, whilst later their potency is comparatively exhausted. In stud-farms, according to the same observer, it is a familiar experience that the most vigorous stallions serving a mare in the morning commonly procreate a filly; but if later in the day they serve a second mare they almost always procreate a colt. This, he thinks, finds its explanation in the fact that the stallion, when he serves the second mare, is in a condition of comparative sexual exhaustion, the more so because he usually covers the first mare twice.

455Maritegoute’s breeding experiments at the sheep-farm of Blanc (Haut-Garonne), on the other hand, gave divergent results. In the early part of the pairing season, as long as the ram’s sexual powers were completely unimpaired, he procreated more male than female lambs. But when a few days later a great number of the ewes were simultaneously on heat and the ram, owing to very frequent acts of intercourse, began to be sexually exhausted, the procreation of female lambs was in excess. But when, finally, this period of maximum demands upon the ram’s powers was past, and the number of ewes on heat became once more small, the procreation of male lambs in preference to female was again observed.

The data obtained by Düsing from the Prussian stud-farms, in which, when greater sexual demands were made on the stallions, more males were procreated, have been already mentioned.

Fiquet made interesting experiments on cows and believed that in this way he was able to demonstrate the influence of nutrition upon the determination of sex—to such a degree, indeed, that he believed it was possible to breed calves of either sex at will. The following method gave him positive results in more than thirty instances. He never had the cow served by the bull at the first heat, but only at the second (if a cow is left unserved when on heat, the heat recurs after an interval of three weeks). The interval of three weeks was utilized in the preparation of cow and bull for the copulatory act. If a bull-calf was wanted the cow was supplied with the most invigorating fodder and was kept on the richest pasture available. The bull, on the other hand, that was to serve this cow was turned out to graze on the poorest pasture and was given poor fodder. At the end of the three weeks, when the cow came on heat for the second time, its sexual appetite was as intense as possible, whereas the bull showed but slight inclination to the sexual act. If the bull now served the cow a bull-calf was procreated. The opposite procedure led to the procreation of a heifer. For this purpose Fiquet kept the cow on low diet during the interval between the first and second heats, and had her first served by a castrated animal. When in this way, and by the low diet, the sexual appetite of the cow had been sufficiently diminished, it was served by a lusty bull, which for a long time had not been put to any cow, and the sexual potency of which had been increased to the uttermost by feeding it for several weeks on the most invigorating fodder.

The results of these experiments, according to which the nutrition 456of the parent-animals before the copulatory act has an influence upon the determination of sex, is explained by Düsing in this way, that nutrition influences also the quality of the reproductive products. “Poor nutrition gives rise to diminished functional capacity of the genital apparatus. Thus, for example, the production of semen is lessened. It can, in fact, hardly be replaced as quickly as it is used up. This occurs when there is a lack of adequate means of subsistence, and also when there is a lack of comparatively young males. In both cases alike we trace the effects in the birth of an excess of males. Converse conditions give rise to an excess of female offspring.”

Passing now to consider investigations made by physiologists, Born, at the anatomical institute at Breslau, has endeavoured to solve the problem of the determination of sex by means of experiment. He employed for this purpose rana fusca, an animal with which positive results can be obtained in a comparatively short period of time. He examined the sex both of the frogs in the free state (165), and also of larvæ which he had bred in specially arranged aquaria. Whereas among the frogs developing in the open, the numbers of the sexes appeared to be approximately equal (there was an excess of females amounting to 2 or 3 per cent.); among those bred in the aquaria there was an enormous preponderance of females (96 per cent.). This remarkable result is referred by Born to the inadequate supply of nutriment in the case of the larvæ bred by him (he fed them on hydræ and on putrefying frog and tadpole meat); from an examination of the alimentary canal of tadpoles caught in the open Born ascertained that their normal food was the mud of the pools in which they were hatched, containing infusoria, radiolariæ, diatoms, algæ, etc. The accuracy of this explanation appeared to Born to be more convincingly shown by the results in the case of one of his twenty-one aquaria. In this one alone the percentage of males was as high as 28 per cent., and the tadpoles in this attained the same size as those developed under natural conditions in the open, whilst in all the other aquaria the tadpoles remained abnormally small. This particular aquarium, owing to an oversight, had pond-mud on its floor, whilst all the other aquaria were floored with clean sand.

A. von Griesheim disputes Born’s results and believes that the latter, determining the sex of the tadpoles by means of a hand lens, must have mistaken a great many female tadpoles for males. He himself, by repeated enumerations of a large number 457of tadpoles (685), part caught in the open and part taken from a large aquarium, found that the ratio between the sexes in the case of rana fusca was regularly 36.7 males to 63.3 per cent. females.

E. Pflüger refers the divergence between Born’s results and his own and those of von Griesheim not to any error made by Born in the diagnosis of the sex of the tadpoles, but to the fact that in the latter’s aquaria the mortality of the male tadpoles was probably greater than that of the females. Pflüger endeavoured to ascertain whether the concentration of the semen might have an influence in the determination of sex. A quantity of frog-spawn was fertilized with concentrated semen, taken direct from the seminal vesicles, and another quantity of spawn was fertilized with diluted semen, obtained by making an aqueous extract of the incised testicles. The ratio between the sexes in the case of the two lots of tadpoles, which were kept in separate aquaria, proved, however, to be mathematically identical. But another experiment showed that the number of males was very different, according to the kind or race from which the animals were derived. He therefore believes that for the character of the development of the reproductive organs, the race of the parent animals is determinative. There is very little likelihood of being able to modify this inherited sexual ratio by means of outward influences affecting the ova and the ripe semen prior to fertilization, and just as little by means of a number of abnormal influences (change of climate, of water, of nutriment, etc.) acting on the fertilized ova.

Düsing,—who in his work on “The Regulation of the Sexual Ratio” (Jena, 1884) most ingeniously advocates the thesis that all animals have the power, when there is a lack of individuals of one sex, of procreating an excess of individuals of this deficient sex, or, to put it in another way, that an excess of one sex determines the procreation of an excess of the other sex,—instituted experimental investigations regarding the determination of sex in the following manner (in accordance with a suggestion made by Pflüger): About ninety guinea-pigs were distributed in two pens in such a way that in one pen there was a great deficiency of males and a great excess of females, whilst in the other there was a deficiency of females and an excess of males. Thus the sexual ratios in the two stalls were opposed. In accordance with Düsing’s theory, therefore, more males should have been born in the first pen and more females in the second pen. Every week each pen was examined once or twice, the sex of the new-born young was ascertained, and they 458were distinguished by small incisions in the margin of the ear. A week later, when the young animals had developed a little further, they were re-examined to make sure that no mistake had been made.

At first, in the pen containing the original excess of females, there occurred a quite remarkable excess of male births. This, however, was merely the result of chance, for soon the relationships of the sexes among the new born was reversed, and thenceforward many more females were born than males. But if all the births occurring in this experiment are taken into consideration the number is still far too small to allow trustworthy conclusions to be drawn.

Düsing emphasizes the fact that such an experiment as this, in order to furnish results worth consideration, must be continued until the sexual ratio has become constant, so that it is no longer subject to alteration by chance variations. If we assume that Düsing’s theory is false, the results obtained would be the following: In both the pens, in that in which there was originally an excess of females and in that in which there was originally an excess of males, the births, if observed through a sufficient period, would present a definite sexual ratio which would be the same in both the pens. But if the theory is well founded the sexual ratio of the new born would vary in the two pens: in the stall in which there had originally been a deficiency of males there would be an excess of births of males over females; whereas in the pen in which there had originally been a deficiency of females there would on the contrary be an excess of births of females over males. Düsing recommends that for such experiments even more fruitful animals, such as rats and mice, should be utilized.

Institutes for pisciculture would also be extremely suitable for such experiments in breeding for the determination of the matter under discussion because, owing to the fact that in these animals fertilization is effected outside of the body of the parents, a direct examination of the ova and the semen used in the experiments can be undertaken, and the fertilization can be made to occur under conditions subjected to various alterations; also we can employ the roe and the sperm of fishes whose age, life history, weight and size are accurately known.

Much attention has recently been paid to the theory of Schenk, based, as he states, upon numerous experiments regarding the influences by which sex is determined. This observer also starts from the principle that ovulation is not independent of the influences of 459nutrition and metabolism. He believes that in the cases in which combustion in the body is effected in such a manner that remnants of unconsumed substances, still capable of heat-production, make their appearance in the urine, the ovum of the human female in process of formation is not so far advanced in its development as it is in cases in which the urine is entirely free from sugar, or at any rate is free from any demonstrable traces of the presence of this body. In the former case we shall find that the ovum is not only less mature, but also that it is presumably less well nourished. In his view such an ovum is less completely endowed in respect of the indwelling qualities and forces of its protoplasm, and it appears for this reason to be adapted only for the development of a female individual. But when, on the contrary, in the maternal individual, all the substances formed in and assimilated by the organism have undergone combustion so completely that there is no sugar in the urine, not even in the minutest discernible traces, the maternal body is in a condition suitable for the development of an ovum adapted to become a male individual. From these inferences, weak though the chain of argument is, Schenk draws the conclusion, that by the regulation of the nutritive material supplied to the organism, and by the suitable choice of that material, we are to a considerable extent enabled to support an ovum in its process of maturation in such a manner as to cause it to develop into a male individual.

The nutritive material selected for this purpose must be of such a nature that the elimination in the urine of even the minutest quantities of sugar may be prevented; the urine must appear free from sugar even when the phenyl-hydrazine test is employed. Thus in every case in which we wish to influence a woman’s nutrition in such a way as to lead to the procreation of a male individual we must above all ascertain whether, in the woman in question, the normal quantity of sugar is present in the urine. If after the most careful examination no trace of sugar can be found in the urine, and if reducing substances are present in this excretion in abundance, no change need be made in the diet, and all we have to do is to recommend that the requisite fertilization should be effected as soon as possible, since there is every probability that in this condition the embryo will prove to be of the male sex. But when, on the other hand the “normal” quantity of sugar is present in the urine, or when even traces only of that substance can be detected, it is necessary by changes in the diet to cause the disappearance from the urine of every trace of sugar, and at the same time to bring 460about the appearance in that fluid of an abundance of reducing substances. Schenk claims by the experiments he has made along these lines to have obtained results which show that it is possible in this way to influence the determination of sex.

His method is to nourish the mother mainly on nitrogenous materials and fat, and to give in addition only so much carbohydrate as is necessary to prevent the absence of this from being seriously felt. This diet should be continued for a considerable period, at best for two or three months before the fertilization is effected. After conception also, the same diet should be continued. In such a manner we are able in certain cases to bring about the procreation of male offspring. On the other hand, the desire for the procreation of female offspring remains one which as yet we have no direct means of fulfilling.

These vague experiments and ill-grounded theories of Schenk’s do not, as a matter of fact, constitute an important advance in the theory of the voluntary determination of the sex of the human offspring. What in reality are the decisive influences in the determination of sex, and how the final impulsion in one direction or the other is actually effected, remain altogether obscure. Prediction of the sex of the offspring, and the voluntary procreation of male or female infants, remain problems for the solution of which the most essential data are still lacking.

Ernest Hæckel writes regarding Schenk’s theory: “This important ‘discovery,’ which at the time of its first announcement attracted throughout the world an attention rarely given to true scientific advances, has now dwindled to the incomplete demonstration that the nutritive condition of the mother exercises a certain influence upon the determination of the sex of the child. But we knew this much a long time ago. Düsing and others, partly by physiological experiments and partly by statistical demonstrations, had shown that changes in the quantity and the quality of the nutriment supplied to either parent is capable of influencing the procreation of boys or girls. But if what Professor Schenk maintains were really true peoples living chiefly upon meat (as, for instance, in the pampas of South America) should have an exceptionally large proportion of male offspring; whereas those living mainly on a proteid-free diet (on meal, sugar, and other carbohydrates), should have an exceptionally large proportion of female offspring (as, for example, the rice-eating Indian and Mongolian nations). But this is by no means the case. And many other well-known facts are 461likewise opposed to the ‘epoch-making’ theory of Schenk. Whether the fertilized ovum develops into a boy or a girl, depends, I am convinced, upon far more complex, and to a large extent still entirely unknown, physiological causes. The final judgment upon the ‘Schenk theory’ must be, ‘Much Ado About Nothing.’”

Our exposition of the present standpoint of the doctrine of the origination of sex in the human species, has, in fact, shown that hitherto by statistical work, nor by anatomical investigations, nor, finally, by the experimental method, have results been obtained which render it possible to predict the sex of the unborn infant. And even in respect of the study of those influences which exercise a determining influence upon the origination of sex, no positive, indisputable conclusions have been reached. We can only say it appears probable that there exist several causes of the determination of sex the co-operative action of which proves effectual. Not in the ovum alone, nor in the spermatozoon alone, but in the reciprocal influence they exert one upon the other in the act of conception is sex determined. In the latter connection the relative and absolute ages of the progenitors appear to have a certain influence in the determination of the sex of the embryo; of importance also is the greater or less demand made upon the sexual capacity of the begetter; of influence too is the time at which the ovum is fertilized after its discharge from the ovary. It appears to be fairly well established that when the husband is at least ten years older than the wife, while the latter is at the age at which a woman’s reproductive powers are at a maximum, more boys are conceived than girls (Kisch); also that one of the progenitors upon whose sexual capacities the greater demands are made, tends to procreate an excess of individuals of his or her own sex (Piquet, Düsing); and, finally, that intercourse a considerable time after the cessation of the menstrual flow (in the second week of the intermenstrual interval or later) is favourable to the procreation of a male infant (Thury, Hensen). The influence of nutritive conditions in the determination of sex is less clearly established.

Statistical evidence has proved beyond dispute that given a sufficiently large number of instances in varying conditions the sexual ratio is 106, and this fact suggests that the determination of sex is dependent upon the interaction of two influences operating in opposite directions within narrow limits, in such a manner that the chances of the birth of a male infant preponderate over the chances of the birth of a female infant in the proportion of 106 to 100. In 462elucidation of this fact Hensen makes the following comparison: “Let us imagine a balance the beam of which has two arms of equal length; from the two extremities of this beam two balls of nearly equal weight begin to roll toward one another; if one ball rolls more quickly than the other, if one is lighter than the other, or if one starts to roll before the other, the opposite end of the beam will sink. The three influences are variously distributed; one influence may reinforce another, or may counteract another; but a decisive sinking of one end of the beam will always ultimately ensue. A minimal shortening or lightening of one arm of the balance will make the chance that the other arm will descend correspondingly greater.”

Sterility in Women.

When we study the history of human civilization we find that sterility in women is regarded, not merely as a misfortune, but as a reproach. Among savage races, and in the Orient, where the position of women is one of strict subordination, she does not attain an honourable status until she becomes a mother. In Persia, a sterile woman is always divorced by her husband. In India, also, when a sterile married woman has in vain employed the various religious measures advocated for the relief of her barren condition she is sent back to her parents. Both in China and Japan, a barren woman is regarded as a most miserable creature. Among the negro races, a woman who fails to bear children is the object of scorn and contempt. Among the Dualla negroes, a man whose wife fails to bear children demands from her parents the return of the sum which he paid for her at the time of marriage. Many of the indigenous tribes of South America also make a practice of divorcing a sterile wife. Among the better-class Circassians, the women do not attain an assured position until they have borne a child. In Angola a barren woman is the object of universal contempt, and she often feels the ignominy of her position so keenly that she commits suicide. Alike among the Jews and among the Turks, barrenness in a wife is a recognized ground for divorce, and the woman who has been divorced for this reason will hardly ever succeed in obtaining another husband, for she is regarded as one whose body is not properly developed. According to old German law, barrenness in a wife and impotence in a husband were both grounds for divorce. The code of the Emperor Justinian allowed of divorce in cases in which for the space of two years a husband had been unable to fulfil his marital duties, and such a union was termed 463innuptæ nuptæ. Among the ancient Romans, although they regarded barrenness as a mark of the divine disfavour, according to the laws of Augustus failure to bear children was a punishable offence, and such a punishment was incurred by any married woman who had attained the age of 20 years without having become a mother. In ancient Greece also, divorces due to the barrenness of the wife were by no means uncommon. Among the Slavonic peoples sterility was so greatly despised that there is a Slavonic proverb which runs: “A woman is no woman until she has borne a child”: and in Istria a sterile woman is known by the nickname “Scirke,” which is equivalent to “hermaphrodite.” The Jewish view of the matter is expressed in the Talmudic rabbinical saying: “A wife’s duties are beauty, gentleness, and the bearing of children”; and again, “the poor, the leprous, the blind, and the childless, are like the dead”; and, finally, “he who refrains from marriage with the deliberate intention of having no children, incurs the guilt of murder.” In the Koran we find the fatalistic expression, “God makes a woman barren in accordance with his will.”

We can therefore readily understand that in the most ancient medical writings the question of sterility in women is a matter of earnest consideration. In the works of the early physicians of Hindustan we find several apt remarks on the subject. Susruta says: “Pregnancy most readily results from intercourse during menstruation. At this time the os uteri is open, like the flower of the water lily in the sunshine.” In the Old Testament, in which the newly-created human couples receive the command, “Be fruitful and multiply, and replenish the earth,” we find frequent references to barrenness as a state equally dishonourable and unfortunate, and the use of certain plants is recommended as a means of cure. The Talmud contains several essays dealing with the causes and treatment of sterility.

The Hippocratic collection of writings contains a number of passages dealing with the causes of sterility and with the means to be employed for its relief. We shall have occasion later to refer to these recommendations. Celsus, on the other hand, has little to say on this subject. In the works of Pliny, and also in those of Aristotle, there are references to the topic of sterility.

Among the writers of the first century of our era, Soranus discusses exhaustively the capacity for conception and sterility. In his work we find, among other passages, the unquestionably accurate remark: “Since the majority of marriages are concluded, 464not from love, but in order to procreate children, it is difficult to understand why, in the choice of a wife, less regard is paid to her probable fertility than to the worldly wealth of her parents.”

In the middle ages, Paulus Agineta more especially treats of the diseases of women, and among these, of sterility in women. That in Arabian medicine much attention was paid to this question, we can learn from the writings of Maimonides.

By sterility in women we understand the pathological state in which a woman who is sexually mature fails to conceive, notwithstanding frequently repeated, normal sexual intercourse throughout a considerable period of time.

Sterility is termed congenital (or absolute) when, notwithstanding repeated intercourse throughout a long period (not less than three years), pregnancy has always failed to ensue; it is termed acquired (or relative), when women who have already been pregnant once or more often, cease to conceive, although they are still quite young enough to do so, and have experienced regular sexual intercourse for a long period (not less than three years). In a wider sense of the term, we say that a woman is sterile, when, notwithstanding prolonged and repeated sexual intercourse, in circumstances favourable to procreation, she has failed to give birth to a living and viable infant.

English authors also make a special distinction regarding that form of acquired sterility (which is no great rarity), in which a woman gives birth to a single infant and subsequently remains sterile (“only-child sterility”).

The civilization of the present day, with its shady side, has made it necessary for us to pay an increasing attention to facultative sterility, dependent upon the use during intercourse of means for the prevention of conception; and very recently the surgical tendency of modern gynecology has brought into being a new variety of sterility in women, viz., operative sterility.

The period which must elapse after marriage, before the absence of pregnancy must lead us to regard a woman as sterile, is fixed at three years. This limitation is based upon the statistical data which (see Table on page 368) I gave regarding 556 fruitful marriages.

The ideal state of fertility, that in which conception is the immediate result of the first act of intercourse between husband and wife, the conception being followed in due course by the birth of a child, 465is, like most other ideals, one very rarely attained. In the human species, conception as the immediate result of the first act of sexual intercourse, is an extremely unusual occurrence. To invoke medical assistance for women who have failed to conceive during the first three months of married life, which my experience shows to be more frequently done now than formerly, is devoid of all justification; and still worse is it, in this period of “early love” to subject women, as has often been done recently by overenergetic gynecologists, to local treatment, even to the extent of operative procedures.

We are not justified in speaking of the existence of actual sterility until three years of marital intercourse have failed to result in conception; still, when the commencement of the first pregnancy is delayed for more than sixteen months after marriage, there is considerable probability that the woman is sterile; and this probability increases month by month till the expiry of the second year, whilst as the end of the third year approaches, it becomes tantamount to certainty.

Sterility is one of the commonest of the functional disorders of women, and one of those which most often demand gynecological assistance.

By a statistical study of the marriages of the royal and princely families of Europe and of the marriages of the highest families of the aristocracy, I learned that of 626 marriages, 70 were barren; thus the ratio of fruitless to fruitful marriages proved to be as 1 : 8.87. But in other circles of society, in so far as data relating to the matter were obtainable in my practice, the statistics of infertility were by no means so unfavourable, the ratio working out at about 1 barren to 10 fruitful unions. I must point out, however, that these statistics, like all statistics of fertility, are to a degree invalidated by the fact that in a certain number of the instances included among the barren, an unnoticed abortion may have occurred.

Simpson, in his investigation regarding the frequency of sterile unions, found a ratio of 1 : 8.5 (in 1252 instances). In the English aristocracy, where the marriages are for the most part restricted among the members of a comparatively small number of families, the ratio was 1 : 6.11 (495 instances); on the other hand, among the population of Grangemouth and Bathgate, consisting chiefly of persons engaged in seafaring and agricultural occupations, the ratio of barren to fruitful unions was as 1 : 10.5.

466Spencer Wells and Marion Sims, as a result of their investigations, give a ratio of 1 : 8.

According to Seeligmann, in Hamburg, among marriages of persons in all classes of society, 11.5% are barren. Prochownick found among 2500 women, all of whom had been married for eighteen months or more, and none of whom were more than 40 years of age, that 9% had failed to conceive.

According to Frank and Burdach, who do not publish the figures upon which their estimate is based, only 1 marriage in 50 proves barren. Lever, who also gives merely his percentage result, states that 5% of married women are completely infertile. Hedin, dealing with a Swedish community of 800 persons, states that the percentage of sterile unions is barely 10.

According to Goehlert’s statistical investigations, in the dynasty of the Capets, among 450 marriages, 19.7% were sterile: in the Wittelsbach dynasty (Bavaria), among 177 marriages, 23.7% were sterile; and among the ruling families of Germany (more than 600 marriages), 20.5% were sterile. In this investigation, however, no attention is paid to the age of husband or wife; marriages and remarriages are classed together without discrimination; and those marriages only in which a living child was born are counted as fruitful, so that the unions counted as sterile must contain many in which abortion or stillbirth occurred. In three Esthonian communities in Livonia, Oehren found that among 2799 marriages, 8.4% were barren, but in this instance also stillbirths were ignored.

Ansell reports that of 1919 marriages of women belonging to the upper classes, their mean age being 25 years, 152 proved barren, a proportion of 1 : 12, or about 8%.

Matthews Duncan communicates the following data. In the year 1855, in the cities of Edinburgh and Glasgow, 4447 marriages were contracted, and of these 725 proved barren, a proportion of 1 : 6.1; 75 of these may however be excluded from consideration, inasmuch as the wives were already at the age of 45 or upwards. Among the remaining 4372 marriages, 662 proved barren, a proportion of 1 : 6.6. In other words, 15% of all marriages of women between the ages of 15 and 44 proved sterile.

From France we obtain figures showing a much higher proportion of sterile unions. According to Rochard, in France in the year 1888, of ten million families, two million had no child at all, and two million had each an only child, so that two fifths of the families of France were taking no practical part in the maintenance of the 467population. According to Chevin, the proportion in France of barren to fruitful marriages is as 1 : 5. 20% are entirely barren, while 24% exhibit only-child-sterility.

From Massachusetts, Morton reports that according to the last census returns, one fifth of all married women are childless.

In England, numerous trustworthy statistics can be obtained regarding the frequency of sterile marriages. The average proportion of barren to fruitful unions was:

Among the patients in St. Bartholomew’s Hospital 1 : 8

Among the inhabitants of Grangemouth 1 : 10

Among the inhabitants of Bathgate 1 : 10

Among the British peerage 1 : 6

Among the upper classes 1 : 12

Among the inhabitants of Edinburgh and Glasgow 1 : 7

Matthews Duncan compiled the following table relating to 504 absolutely sterile women met with in his practice:

Age at Marriage. Number of Years Married.

Less than 3. 4 to 8. 9 to 13. 14 to 18. 19 to 23. 24 to 28. 29. Totals.

15 to 19 12 19 15 4 7 2 1 60

20 to 24 70 66 37 24 13 9 219

25 to 29 47 51 20 8 8 134

30 to 34 26 20 8 1 59

35 to 39 6 13 4 23

40 to 45 6 3 9

Totals 167 172 84 40 29 11 1 504

Ansell bases upon the observations made by him in the case of 152 sterile women the conclusion that there is no longer any chance of the occurrence of pregnancy if a woman is:

More than 48 years old, and has had no child for 2 years

More than 47 years old, and has had no child for 3 years

More than 46 years old, and has had no child for 4 years

More than 45 years old, and has had no child for 6 years

More than 44 years old, and has had no child for 8 years

Less than 44 years old, and has had no child for 10 years

If we take into account also cases of acquired sterility, the proportion of barren to fruitful marriages becomes even more unfavourable, and the proportion increases enormously if, with Grünewaldt, we number among the barren women those who fail to continue child-bearing up to the normal climacteric period. Grünewaldt, dealing with about 1500 women suffering from affections of the reproductive organs, excluded all those who were either virgins 468or widows, and also all those who at the time of the observed barrenness were over 35 years of age; this left more than 900 women suffering from affections of the reproductive organs, all of whom were sexually mature, and were living in marital intercourse; of these, nearly 500 were barren, 300 being instances of acquired sterility, and 190 instances of congenital sterility. Thus, according to this observer, disease of the reproductive organs in women led in more than 50% of the cases to disturbance of the reproductive capacity; about one in every three women, previously competent to bear children, became barren when affected with disease of the reproductive organs; and among every five gynecological patients of the condition already specified as regards age and sexual intercourse, one proves congenitally sterile.

It must not, however, be forgotten, that sooner or later after marriage artificial sterility tends to come into being, its early or late appearance depending upon the degree of civilization and upon the national and economical conditions of the people and the individuals concerned. This fact must not be left out of the account.

The manner in which, in the human species, fertilization is effected, is still far from clear in all its details; hence it is easy to understand, that the etiology of sterility remains in many respects obscure. It is impossible in every case to find a definite cause. Whereas, on the one hand, notwithstanding the existence of apparently insuperable obstacles, impregnation may nevertheless be effected; so, on the other hand, sterility may exist in cases in which all the circumstances appear favourable to the occurrence of conception. Hence a classification of the different varieties of sterility from the etiological standpoint, is a very difficult task, and the conclusions thus obtained are often vitiated.

Although it cannot be denied that mechanical causes are competent to lead to sterility in women, Sims, in his advocacy of the mechanical doctrine of sterility, widely overshoots the mark. His authority, however, has led to a general acceptance of this doctrine, which is by no means justified by facts. The theory of mechanical obstruction, according to which sterility in women depends upon mechanical obstacles to the passage of the spermatozoa towards the ovaries, is from time to time strikingly illustrated by cases coming under our notice—cases the nature of which can hardly be overlooked; but it is quite wrong to suppose that this causation accounts for the majority of instances of sterility in women, and 469strict limitations should be placed upon the employment of surgical measures based upon this mechanical theory of sterility.

The mechanical view has been counterposed by Von Grünewaldt with a doctrine in which especial stress is laid upon obstacles to utero-gestation, sterility being regarded as a functional disorder brought about by affections of the female reproductive organs rendering the uterus unfit for the incubation of the ovum. It cannot be denied that the elucidation of this casual influence was a valuable contribution to the theory of sterility, and it is unquestionable that many morbid conditions of the uterus exist capable of giving rise to sterility in this manner; but we must avoid the error of regarding this doctrine as a full explanation of the cause of sterility.

If, however, both of these theories of sterility are insufficient, we cannot regard a third theory, that of Matthews Duncan, as filling the gaps in our knowledge. It would be most unfortunate if this author were right in maintaining that all our knowledge of the causes of sterility is to be summed up in the phrase “deficient reproductive energy;” we cannot agree with Duncan in his belief that “Sterility is an imperfection devoid of all perceptible, measurable characteristics;” nor can we follow him when he maintains that local causes, whether they are such as hinder conception, or such as hinder utero-gestation, have a very limited sphere of activity. Matthews Duncan adopts an incomprehensible standpoint when he regards sterility as dependent upon a law of nature, as a condition which may affect distinct classes or an entire population.

According to the latest doctrine of sterility, only in quite exceptional instances is the woman regarded as responsible for the occurrence of sterility; contrariwise, the male genital organs are commonly blamed for the affection, which is in the overwhelming majority of cases supposed to be due to azoospermia, usually dependent upon gonorrhœal infection; compare with this, affections of the female reproductive organs are said to play a quite subordinate role in the etiology of sterility. But for my part, though I recognize the important share that gonorrhœa in the male plays in the causation of sterility, I am of opinion that the extreme view just mentioned is by no means justified by the facts.

Sterility, a functional disturbance of an extremely complicated nature, can, in my opinion, be most usefully elucidated from the etiological standpoint by starting with the assumption that three conditions are absolutely essential to procreation:

4701. that ovulation proceeds in a perfectly normal manner, the maturation of the discharged ova being complete;

2. that normal spermatozoa have access to these normal ova (conjugation of male and female pronuclei);

3. that the uterus is properly adapted for the gestation of the fertilized ovum.

My classification of the varieties of sterility corresponds to these conditions of procreation:

1. sterility due to incapacity for ovulation;

2. sterility due to some hindrance to the conjugation of ovum and spermatozoon (under this head come also those cases in which the male is at fault—azoospermia, and the like);

3. sterility due to incapacity for gestation.

It must also be admitted that there are additional causes of sterility, causes which lie beyond our control. Moreover, as I have already mentioned, in most cases of sterility, we have to do, not with a single cause, but with the resultant of two or more cooperating causes.

Incapacity for Ovulation.

Incapacity for ovulation, the first and most decisive cause of sterility in women, may be absolute and irremediable, or relative and transient. We have to do with the former in cases in which the ovaries are entirely wanting, or when they are affected with organic disease to such a degree that they have become incapable of fulfilling their function of ovulation; incapacity for ovulation is, on the other hand, relative and transient in certain pathological states of the ovary and neighbouring organs, when there is incomplete development or partial atrophy of the ovaries, when there are new-growths of the ovaries, in cases of oophoritis and perioophoritis, in consequence of disturbances of innervation, diseases of the central and peripheral nervous system, violent emotional disturbance, constitutional disorders, such as syphilis, chlorosis, anæmia, universal lipomatosis, scrofula, alcoholism, and morphinism, also in consequence of changes in the supply of nutriment and in the general mode of living, or of senile changes, and finally in consequence of hereditary influences.

The diagnosis of the etiological influence of suppressed or incomplete ovulation in the production of sterility in women is at times beset with great and even insuperable difficulties. The state of the menstrual function, suppression of the flow, or the regularity or irregularity of its occurrence, serve indeed to inform us as to 471the general activity or inactivity of the function of ovulation; but the variations in this function give no certain information as to whether a woman is fertile or infertile. Knowing as we do that generally speaking an intimate connexion subsists between menstruation and ovulation, we are indeed able to assert that regular menstruation and fertility in women run a parallel course, and further, that the greater the irregularity of the menstrual function, the greater the tendency to sterility. Recently, great advances have been made in the technique of manual exploration of the ovaries, and by means of vaginal and rectal bimanual examination, we are now able to obtain accurate information regarding abnormalities in the size, shape, and position of these organs, and regarding any other intrapelvic disorders. In this way we have been enabled to recognize a number of pathological states of the ovaries which affect the functions of these organs. In some cases also there are general symptoms which furnish us with the means of drawing conclusions, more or less trustworthy, regarding the state of the ovarian functions; for instance, the general development of a woman’s body, the condition of the external genitals, the vulva, the mons veneris, the pubic hair, the clitoris, and the mammae. Again, we can derive information from various troubles of which women complain; such as sacrache; a sense of weight and pressure in the pelvis; feelings of tension and shooting pains in the breasts; flushings of the face; haemorrhage from the nose, mouth, or rectum, recurring at regular intervals and vicarious in nature. In many instances, however, it will only be by obtaining data regarding the age, mode of life, and family history, of the person affected, that it will be possible to draw conclusions as to the cause of the sterility.

The female reproductive glands, the ovaries, may, owing to developmental disturbances during foetal life, either be entirely wanting, or they may merely be deprived of certain structural constituents, especially their epithelial elements. In the former case, we have congenital complete unilateral or bilateral absence of the ovary, a condition most commonly associated with the absence or with a rudimentary condition of other portions of the reproductive apparatus; in the latter case, we have the condition somewhat inappropriately named congenital atrophy of the ovary.

Complete absence of both ovaries necessarily leads to absolute sterility. Both congenital absence and congenital atrophy of the ovaries, will usually be found in association with other anomalies of the sexual organs. Absence of one ovary, on the other hand, by no means entails sterility; on the contrary, when a single well-formed ovary exists, ovulation usually proceeds in a perfectly 472normal manner. When such women marry, pregnancy usually follows in the normal proportion of cases; and, in complete opposition to one of the theories of the determination of sex to which allusion has been made, such women bear children of both sexes.

Morgagni described a case of congenital absence of both ovaries in a woman 66 years of age, in whom the external genital organs, the vagina, and the uterus, were imperfectly developed, but the Fallopian tubes were of normal size. Careful examination of the upper borders of the broad ligaments of the uterus disclosed no trace of ovary on either side.

Quain, in a virgin 33 years of age, found the vagina rudimentary, with its mucous membrane but slightly corrugated; at the upper end of this passage was a semilunar fold which probably represented the uterus. The ovaries were absent; a small gland-like body embedded in the left wall of the vagina was regarded by him as a rudimentary ovary. The configuration of the body was feminine, feminine also the disposition; moreover, there was a monthly recurrent epistaxis.

The atrophy of the ovaries which normally takes place at the climacteric period, to be more minutely described in the section on the menopause, has constitutional effects similar to those dependent upon absence or congenital atrophy of the ovaries.

A rudimentary condition of both ovaries, or bilateral atrophy of these organs, with or without associated atrophy of the entire reproductive system, commonly entails sterility. In such cases, in addition to amenorrhœa, we usually find that the breasts are but slightly developed, the pubic hair is scanty, the labia majora and labia minora are small, whilst sexual appetite is deficient, and during coitus the woman is entirely passive. On the other hand, we must not make the mistake of inferring from the fact that the sexual appetite is keen and coitus pleasurable, that therefore the capacity for ovulation is normal. Even after operative removal of both ovaries, some women have assured me, not only that the sexual impulse was as strong as formerly, but even that they continued to experience the sexual orgasm in its full intensity. This is analogous to the well known fact that men who have undergone castration after arriving at sexual maturity may remain capable of performing coitus. It is a matter of history that in the lupanars of ancient Rome, castrated men were kept to enable women to enjoy the pleasures of sexual intercourse without fear of consequences; and it is said that such men are to be found in Italian brothels to this day. In the case of the lower mammals, it appears to be the rule that when the reproductive glands are removed in early youth, every trace of sexual desire disappears.