All these mechanical occlusive pessaries are open to the objection that they are apt to give rise to irritative conditions of the genital organs, causing offensive discharges, pruritus, etc. (Recently in order to diminish this drawback, the pessary has been constructed of vulcanized cambric, instead of rubber, and appears then to have a less irritating effect.) Still worse is the injury to the uterus and to the cervical mucous membrane caused by certain intra-uterine instruments which have been recommended for the prevention of conception. The latest of these is an “obturator,” consisting of a silver or silver-gilt tube, which is passed through the os uteri into the interior of the uterus, and left in situ. It is claimed for it that “it allows the menstrual discharge to flow freely away, but renders the entrance of the spermatozoa extremely difficult.” Biermer reports five cases in which serious injury to health followed the use of one of these obturators. In one of these cases in which there were very severe pains and a discharge from the uterus, Biermer removed from the interior of the uterus a broken wing of the obturator; the patient died, however, and the autopsy disclosed perforation of the uterus. In another of the cases the apparatus was also broken.

Less dangerous is the recently invented tampon-speculum. This is passed into the vagina by the woman herself, in order that through it she may, by means of a special introducer, insert a tablet of boric acid, hydrochlorate of quinine, citric acid, or some other substance lethal to the spermatozoa. Without some such instrument, the introduction of these “ovals” to the proper place is often found difficult by women.

A very remarkable means of bringing about artificial sterility, one resembling the operative procedures sometimes adopted in western countries, is employed in various parts of the world, and notably in the East Indies and in the Sunda Islands, namely, the induction of an artificial malposition of the uterus, more especially of anteversion. Thus, van der Burg writes from the Dutch Indies: “In the girls the sexual impulse develops very early, and is gratified without fear of consequences, when the services of certain skilled elderly women have been requisitioned.” These women appear, in fact, to understand, by means of pressure, rubbing, and kneading, through the abdominal walls (not by the vaginal route), how to induce anteversion or retroversion of the uterus, to such an extent as to prevent the occurrence of conception. It is said that the only inconvenient consequences of this procedure are trifling pains in the lumbo-sacral and inguinal regions, and some trouble in passing water during the first few days after the manipulations have been effected. Later, when a girl who has been treated in this way wishes to marry and become a mother, by a reversal of the manipulations the uterus is restored to its natural position. It is said that these skilled women have been called in by European women in the Dutch Indies, who did not wish to have many children; but it appears that in a woman who has once given birth to a child, the result of the manipulations is less to be depended upon, than in the case of a virgin.

A means of ensuring artificial sterility, which in all civilized states is punishable as a criminal offence, and which is nevertheless very frequently practised, is the artificial induction of abortion. Especially in North America it would appear that there exist regular professional abortionists. In this connection, Thomas, the well-known American gynecologist, writes as follows: “Statistics showing the frequency of criminal abortion are not, and probably never will be, available, for this crime cannot be adequately controlled by human society, and commonly eludes legal punishment. It seems a hard saying, but it is a true one, to assert, that the law pursues unremittingly him who has killed his fellow-man, while it leaves immune him who has killed the embryo in the mother’s womb. On my table there lies at this moment one of the most widely circulated, most respected, and most carefully edited daily newspapers of New York—a paper which finds its way into the best circles of society, and also into the hands of girls and women throughout the country. In its columns I find fifteen advertisements which emanate beyond all question from professional abortionists—from men and women who gain their livelihood by child-murder.”

O. Reyher remarks also that in American newspapers advertisements such as the following are of every-day occurrence: “Pills for the regulation of the periods. Ladies expecting to be confined are warned not to use them on any account, for if they do so abortion will infallibly ensue.”

Emmet, in his “Textbook of Gynecology” also complains of the terrible frequency of criminal abortion, so that “every day we see more unhappiness and misery result from the misuse of conjugal relationships than we see in an entire month as a result of births which take place in a natural manner.”

The American Medical Congress offered a prize for a brief and readable essay, suitable for diffusion among women, showing the criminality and the physical harmfulness of artificial abortion. The prize was awarded to Storer’s essay, entitled “Why Not?”

Among the ancient Greeks, the fear of over-population led to the practice of homosexual intercourse. The states of ancient Greece were in most cases of a very small area, so that a very moderate increase in population would render the means of subsistence insufficient. Hence intercourse with women was avoided, and the sexual impulse was gratified in unnatural ways. Inspired by this fear of over-population, Aristotle urged upon men that they avoid women, and should indulge in the love of men and boys, and at an earlier date, Socrates had celebrated the love of boys as a mark of higher culture. The most notable men of classical Greece practised homosexual intercourse; authors and poets celebrated the love of boys. Stimulated by their example, Sappho of Lesbos became the inspired poetess of the love of women for members of their own sex (Lesbian love).

Among the Romans it was rather satiety in consequence of sexual excesses which led in that country to the diffusion of the Greek love of boys; the consequent childlessness diminished to such an extent the numbers of the Roman burghers and patricians, that Augustus, in the year 16 B. C., enacted the Julian law, by which the procreation of children was rewarded, whilst celibacy became a punishable offence.

At the present day the fear of an excessively large number of children, in relation to the property possessed by the parents and in regard to nutritive possibilities, has led among whole classes, and even among entire nations, to the adoption of preventive measures in sexual intercourse; these measures have, in fact, been developed into a system, which finds adherents among all strata of the population, but more especially, as it is easy to understand, among certain well-to-do sections of the community. In France this system has been adopted to such an extent as to amount to a national calamity.

In few countries of the civilized world, remarks Bebel, are marriages so frequent, relatively to the population, as they are in France, whilst in no country is the average number of children per marriage so small, or the increase of population so slow. The French bourgeoisie long ago adopted this system, and the peasantry and the artizan classes are following their example. In many parts of Germany the same causes have led to the same results. In France, in addition to the prevention of pregnancy and the practice of artificial abortion, infanticide and the exposure of children are also actually employed to keep down the population.

Operative measures for the production of artificial sterility have been practised from very ancient times, and by civilized and savage peoples alike. According to Strabo, the ancient Egyptians and Lydians were acquainted with the art of removing the ovaries from girls and women. The kings of Lydia, Andromytes and Gyges, had the women of their harems castrated, ut iis semper ætate et forma florentibus uteretur. Von Micklucho-Mackay reports that in some parts of Australia the indigens remove the ovaries of certain girls, in order to provide their young men with hetairæ who cannot possibly become pregnant. M. Gillirray saw at Cape York a native deaf and dumb woman whose ovaries had been removed, to prevent her procreating deaf and dumb infants.

We cannot refrain from reference to the astounding proposal of C. A. Weinhold, contained in his work upon the over-population of Central Europe and its consequences to the countries concerned and to civilization in general. He advises, “as a general and urgently required measure, the widespread practice of a sort of infibulation, which is to be undertaken at the age of fourteen and preserved until marriage, and is to be performed in the case of all those individuals who can be proved not to possess sufficient property for the upbringing of an infant, if they should become pregnant as a result of extra-conjugal intercourse. And in those who never attained a financial position in which they might be able to bring up a family, the infibulated condition should be allowed to persist throughout life!”

This proposal is, in fact, no novelty, inasmuch as the bringing about of an artificial adhesion of the labia with a view to the prevention of conception—the operation of infibulation—is practised by many savage peoples. According to the detailed account given by Ploss-Bartels, this operation, in which the inner surfaces of the labia majora are freshened, stitched together, and allowed to adhere, is practised by the Bedschas, the Gallas, the Somalis, the inhabitants of Harrar, at Massaua, etc. The purpose of this practice is to preserve the chastity of the girls until marriage, when the reverse operative procedure is undertaken. If the husband goes away on a journey, in many cases the operation of infibulation is once more performed upon his wives. Slave-dealers also make use of this operation so as to prevent their slaves from becoming pregnant. It is reported, however, that the operation does not invariably produce the desired effect. Hartmann informs us that in Nubia, in Senaar, and in part of Kordofan, the præputium clitoridis or the entire clitoris is cut away, and the margins of the nymphæ are then freshened and stitched together, so that the only aperture left is one sufficiently large for the outflow of the urine.

Brehm states that the operation is performed by old women, who make the necessary incisions with razors; shortly before marriage, the bridegroom sends the girl’s relatives a model of his penis, carved in wood, according to the size of which an aperture is made between the adherent nymphæ; when the woman becomes pregnant, the incision is still further enlarged. In the kingdom of Darfur, the labia majora as well as the nymphæ are freshened and stitched together. In the Berber country, Werne became acquainted with a young widow whose husband had had her submitted to the operation of infibulation no less than seven times. Another somewhat less brutal method of performing infibulation is described by Ploss, as being practised by many Eastern races; a ring is fastened through the labia in such a way as to guard the introitus vaginæ In Europe, during the Middle Ages, such and similar apparatus (“girdles of chastity”) are said to have been employed for the protection of the honour of an absent husband.

Of gynecologists who have advised operative measures for the prevention of pregnancy, in women in whom that condition involved serious dangers, the first, as far as I know, was Blundell. As a result of experiments made on rabbits, he suggested division of the Fallopian tubes as the best way of attaining this end. Later, Froriep and Kocks also endeavoured to induce artificial sterility in women by occlusion of the Fallopian tubes. Froriep’s idea was to bring about obliteration of the lumen of the tubes by means of cauterization with nitrate of silver; Kocks constructed for the same purpose a galvano-caustic uterine sound. But, in the first place, both the methods advocated are too uncertain to be relied upon; and, in the second place, their application is neither easy, nor devoid of serious risk.

Much more effective, however, is the method recommended by Kehrer for the sterilization of women, namely, division of the Fallopian tubes by the vaginal route. Kehrer considers that the physician is justified in preventing the occurrence of pregnancy in a number of morbid conditions—incurable nervous, cardiac, pulmonary, gastric, and renal disorders; various constitutional affections; and, finally, in cases of pelvic deformity of such a degree that the delivery of a living child is impossible except by means of Cæsarean section, but the patient does not wish to be exposed to the risks of this operation. He believes, moreover, that all the methods commonly recommended for the prevention of pregnancy are untrustworthy. So powerful, however, is the sexual impulse, that, as experience shows, the mere prohibition of sexual intercourse, however earnestly made, invariably proves ineffectual. For coitus interruptus to be effective, the interruption must occur at the right moment; and this does not always take place. Cold water douches after coitus are unhygienic; douches of warm water, medicated with sublimate, alcohol, and other drugs lethal to the spermatozoa, are indeed rationally conceived, but often fail of their effect, either because they are deferred until too late, or else because they fail to irrigate all parts of the vagina. Plugs of cotton wool, sponges, etc., are not always introduced in such a way as effectually to occlude the vaginal passage. A suitable and properly introduced occlusive pessary is, indeed, a relatively trustworthy preventive apparatus, but if worn continuously it is apt to become very foul. A thorough douching of the genital passage with an antiseptic solution, performed by the skilled hand, immediately after coitus, would doubtless destroy the spermatozoa with the like certainty with which the same procedure destroys micro-organisms when performed prior to a gynecological operation—but when carried out by the layman, the value of the method is more than doubtful. The operation, for a time actually fashionable, of extirpation of the uterine annexa, certainly gives rise to sterility, but entails the serious disadvantage that the consequent premature menopause is attended by the same disturbances as the natural change of life. On the other hand, section and ligature of the Fallopian tubes is considered by Kehrer to induce sterility without in any other way disturbing the functions of the female reproductive organs. By means of anterior colpotomy we obtain a suitable route for the ligature and section of both tubes at the isthmi. When carried out with the proper antiseptic precautions the operation is almost entirely free from risk; and when the organs are healthy the closure of both the upper and the lower segments of the tubes is effected, and no retention of secretions need be feared as a result of the operation.

With regard to the indications for the performance of this operation, Kehrer insists that it should be undertaken only in cases of serious disease, and when the pros and cons have been conscientiously weighed. A consultation is also indispensable. Moreover, it is essential that husband and wife should both fully understand the nature of the proposed operation, and should form an unbiassed judgment regarding its advisability. To avoid any possibility of subsequent reproaches, Kehrer advises that a written report should be drawn up, giving the reasons for undertaking the sterilization, and that this should be subscribed by the physicians in consultation, by the patient herself, and by her husband.

Recently Pincus has recommended the cauterization of the uterine cavity with superheated steam (atmocausis, castratio uterina). He advises it only in women who are incurably ill (tuberculosis, morbus Brightii, hæmophilia), so that pregnancy and parturition would involve almost certain death.

Kossmann considers that when pregnancy and parturition will endanger a woman’s health and life, it is the physician’s duty to acquaint both husband and wife with this fact; but having done so his duty is fully discharged. “If, after being warned, the married pair choose to indulge in sexual intercourse, they have knowingly and voluntarily run into danger, and for this the physician is in no way responsible.”

As indications for facultative sterility Levy enumerates tubercular disease of the lungs, mental disorders, severe organic or functional diseases of the central nervous system, active syphilis (in certain circumstances), pernicious anæmia, hæmophilia, diabetes mellitus, severe heart disease, chronic disease of the kidneys or liver, certain pelvic deformities, and the tendency to habitual abortion.

I have myself before now stated my opinion that it is the duty of the physician, in the case of a married woman suffering from heart disease, with due regard to the danger which pregnancy will entail upon her, to give needful advice in the matter of the prevention of conception. In women affected with valvular heart disease, and in whom there are serious disturbances of compensation, conception is absolutely to be avoided; also in conditions of marked cardiac degeneration, and when there are distinct symptoms of insufficiency of the heart muscle. When, on slight exertion, palpitation, increased frequency of the pulse, and respiratory need (“air-hunger”), ensue; when there is extensive œdema of the lower extremities which persists even after confinement to bed; when the pulse readily becomes arhythmical both in respect of the strength and the temporal succession of the beats; when the urine is scanty and contains varying quantities of albumen; when there are frequent attacks of heart-weakness, with a small irregular pulse, coldness of the extremities, a cyanotic tint of complexion, nausea, dyspnœa, sense of faintness, or actual syncope—in all such cases, whether dependent upon valvular disease, on pathological changes in the arteries, or upon disease of the myocardium, the occurrence of pregnancy is a true disaster, giving rise in most cases to a grave aggravation of the heart trouble and often enough costing the patient her life. I further regard it as a sound medical axiom that in cases of cardiac disorder of a less severe type than that just described the woman thus affected should not have more than one or two children. This is the more necessary because with each successive pregnancy the functional capacity of the diseased heart decreases in geometrical progression and the danger to life proportionately increases. But in such cases of heart disease the prevention of pregnancy must never be effected by the interruption of coitus by the man before ejaculation, for the reason that this procedure gives rise to manifold reflex cardiac troubles, and especially to paroxysms of tachycardia, with simultaneous diminution in vascular tone, vasomotor disturbances, and states of mental depression—and these entail exceptional dangers in women suffering from heart disease.

The Determination of Sex.

The problem of the determination of sex in the human species is one which has occupied natural philosophers from the very earliest times, and has always greatly interested all classes of the population.

The interest awakened by the subject depends principally on the fact that female children have usually been less desired than male in all periods of history and among almost all races. In the uppermost circles of society the truth of this statement is manifested by the fact that the birth of a prince is announced by a salute of 101 guns, that of a princess by a salute of 35 guns only.

It would serve no useful purpose to transcribe here the opinions, or rather guesses, which were ventured on this topic in earlier days when the very nature of the reproductive process was still entirely unknown, and we shall merely mention that the curious will find various references to the determination of sex in the works of Hippocrates, Aristotle, Plutarch, Soranus, Susruta and Galen.

Broadly speaking, the earlier theories may be said to diverge in two main directions, some holding that the sex of the infant was in some way determined by the mode of intermixture of the male and the female elements in the act of generation, and others maintaining that sex was already inalterably predetermined at the time of intercourse either in the male or in the female sexual elements.

Pari passu with the modern development of the theory of evolution, and with the enormous increase in recent days in anatomical and physiological knowledge, the theory of the determination of sex has been very widely extended. The rival views may be briefly arranged in the four following categories:

I. That sex is already inalterably predetermined in the ovum, upon the constitution of which it solely depends; there are therefore male and female ova, and the process of fertilization exercises no influence whatever upon the determination of sex. The alternative theory to the above, that sex is determined solely by the constitution of the fertilizing spermatozoon—i. e., that the spermatozoa, and not the ova, are male and female, respectively—is one which in recent years has tended more and more to disappear from the field.

II. That sex is determined in the moment of fertilization by the reciprocal interaction of male and female, of zoösperm and ovum. One variant of this theory maintains that each reproductive element strives for the reproduction of its own sex; that a struggle takes place and that the victor in the contest stamps its own sex-likeness upon the fertilized product. According to another view, however, sex is not directly transmitted in this manner; it is supposed that the more powerful the proper reproductive element (according to this theory the ovum) the more strongly does it tend to determine the reproduction of a stronger, i. e., a male organism; thus the greater potency of the female element in the act of reproduction tends to favour the determination of the male sex.

III. That sex is not determined until after fertilization, during the early stages of the development of the embryo; the determining causes are supposed to be various factors capable of influencing the developing organism during this period, and more particularly the nutritive conditions of the mother.

IV. That the determination of sex is not dependent solely upon the action of any single one of the factors above enumerated, but arises as a resultant effect of the operation on the germ of all three of these acting in temporal succession.

Modern physiology has endeavoured to solve this problem by statistical investigations, by anatomical demonstration, and finally by experiment.

I. Statistical Investigations.

Statistical data have been collected showing the ratios between male and female births in the most varied conditions possible, and from these data the attempt has been made to draw valid conclusions regarding the causes of the determination of sex. Now in the first place it is above all necessary to bear in mind that such statistical data cannot possibly have any value unless they relate to very numerous instances, and even then they are liable to be invalidated by various sources of fallacy. We may with advantage quote in this connection the remarks of Hensen in his work on the “Physiology of Reproduction:” “Each individual instance is rendered unique in kind by the interaction of certain incommensurable elements; for instance the state of health of the individual organs in their innumerable combinations, variations in the general health of the parents, the frequency of coitus and the time at which it took place, the desire of the parents to have a son and then no more children, their social position—in these ways innumerable complications are introduced into the problem, and the difficulty of drawing valid conclusions is rendered almost insuperable, unless the number of instances dealt with is enormously large.”

One fact definitely established is that more boys are born than girls, the proportion between the two, known as the sexual ratio, being 106 : 100. Statistics relating to the half of Europe (Oesterlen) and dealing with 59,350,000 births, showed a ratio of 106.3 male to 100 female births; in individual countries variations from this mean are found to occur, but these are not very extensive, the highest ratio being 107.2 : 100, and the lowest ratio 105.2 : 100.

From the works of Hofacker (“Ueber die Eigenschaften welche sich bei Menschen und Tieren von den Eltern auf die Nachkommen vererben”—Concerning the Qualities transmitted from Parents to Offspring in Men and Animals—Tuebingen, 1828) and Sadler (“Law of Population,” London, 1830) conclusions have been drawn regarding the effect of a variation in the age ratio of the parents on the determination of sex. The deductions in question, known as Hofacker and Sadler’s law, are as follows:

1. If the husband is older than the wife more boys are born than girls.

2. If husband and wife are the same age somewhat fewer boys are born than girls.

3. If the wife is older than the husband the excess of female births is larger still.

Hofacker’s actual figures were the following:

Sadler’s results were closely similar:

Goehlert found that the offspring of marriages in which the husband was younger than the wife were 71 boys and 86 girls; of marriages in which husband and wife were of the same age, 263 boys and 282 girls; and of marriages in which the husband was older than the wife, 2,017 boys and 1,865 girls.

Wappaeus, combining the data supplied by these three investigators, Hofacker, Sadler and Goehlert, obtained the following sexual ratios for the entire 8,000 cases (i. e., the number of boys born to each 100 girls born): When the husband was younger than the wife, 88.2; when husband and wife were of the same age, 93.5; when the husband was older than the wife, 113.0.

It will be observed that the mean sexual ratio of these 8,000 cases is 109.6; whilst, as we saw above, when a sufficiently large number of instances is taken, the sexual ratio always closely approximates to 106.3. From this it appears that the numbers dealt with by Hofacker, Sadler and Goehlert in their investigations were too small for the deduction of trustworthy averages.

The same criticism is applicable to the observations of Ahlfeld, Breslau and Noirot, whose results conflict with those just given. According to Ahlfeld, in the case of 1,376 births where the father was at least 10 years older than the mother, the sexual ratio was only 98.2. According to Noirot’s data, in cases in which the father was older than the mother, this ratio was 99.7.

Oesterlen gives the following brief summary of the researches made for the establishment and confirmation of the law of Hofacker and Sadler:

The law of Hofacker and Sadler cannot be regarded as possessing universal validity, although the figures on which it is based seem to show pretty clearly that we are justified in regarding the mutual interaction of the male and female reproductive elements at the moment of fertilization as effective in the determination of sex. In the investigations to which we have hitherto alluded it is only the relative ages of husband and wife that have been taken into account; but other researches have shown that the absolute age alike of the husband and of the wife has an influence in the determination of sex.

The influence of the absolute age of the mother in the determination of sex has been very clearly established. Ahlfeld was the first to draw attention to the fact that among the children of elderly primiparæ there was always to be found an excess of boys, and that there was an increase in this excess proportionate to the greater age of the mother. Among 102 children born to primiparæ over 32 years of age the sexual ratio was 137 : 100; and a later investigation made by the same author in conjunction with Schramm showed that among 1,038 children born to primiparæ over 28 years of age the sexual ratio was 124 : 100.

Hecker obtained similar results. Among 432 children born to primiparæ over thirty years of age the sexual ratio was 133 : 100. Winckel, dealing with primiparæ of the same ages, found a sexual ratio of 136.8 : 100.

Düsing, examining the records of the lying-in hospitals of Leipzig, Dresden and Jena and thus obtaining a very large number of instances whereon to base his conclusions, confirmed the view that elderly primiparæ give birth to an excess of boys, and further that the older they are the larger the excess of male births. He drew up the following table:

As an explanation of this statistically proved fact, that elderly primiparæ gave birth to a large excess of boys, Düsing suggests that these women who conceive for the first time comparatively late in life, are, prior to the conception, in a state corresponding with that of a lower animal species suffering from a deficiency of males, and for this reason exhibit a tendency to procreate a larger number of individuals of the deficient sex. In multiparæ also it is possible to trace the influence of a deficiency of male individuals. When there is such a deficiency the interval between successive births is unduly protracted. Düsing found (once more from the records of the lying-in hospitals of Dresden, Leipzig and Jena) that the longer the interval between one parturition and the next the longer, that is to say, the mother has had to wait for her next conception, the greater is the excess of male births. Düsing therefore lays down the law: “Delayed impregnation gives rise to an excess of male births.”

Bidder considers that his own observations entitle him to modify Ahlfeld’s dictum regarding the influence of age in primiparæ in giving rise to an excess of male births. He tabulates his results as follows:

and formulates the following thesis: Very young primiparæ give birth to an excess of boys; primiparæ in the first bloom of womanhood give birth to an excess of girls; later, however, as the age of the primiparæ increases the excess of male births soon reappears and rapidly increases.

Hofacker’s data and the researches of Hampe agree with those of Bidder in showing that to very young primiparæ, as well as to elderly primiparæ, an excess of boys is born. Among the offspring of 363 mothers, at ages varying from 16 to 26 years, Hofacker found the sexual ratio to be 121; among the offspring of 1,056 mothers, at ages 26 to 36, the ratio was 101; and among the offspring of 567 mothers at ages 36 to 46, the ratio was 111. Hampe tabulated 5,992 instances as follows:

We learn, therefore, that if the age of the progenitors is to be regarded as one of the causes by which sex is determined, we must take into consideration not only the relative ages of husband and wife but, in addition, the absolute age of the wife.

Goehlert undertook a statistical investigation in which the absolute age of the husband was taken into consideration as well as that of the wife. From this it appeared that the maximum sexual ratio was exhibited when the father was between the ages of 30 and 35 years. When the age of the mother is treated as the determining influence, we find the maximum sexual ratio in the offspring of mothers between the ages of 25 and 30 years. Goehlert believes, however, that the paternal influence is more powerful than the maternal in the determination of sex. The respective influences are compared in the following table:

Geissler, studying the data obtainable regarding the sexual ratio during a 10–year period in the Kingdom of Saxony, ascertained that in families possessing two children or more there was a very definite distribution of the possible sex-combinations. Where there was an even number of children those families were in the majority in which the number of boys and girls was identical. If the number of children in the family is an unequal one, those combinations are most frequent in which the number of boys exceeds the number of girls by one; next in frequency are those combinations reversed to this, i. e., in which the number of girls exceeds the number of boys by one. All other combinations are comparatively infrequent in proportion as the discrepancy in number between boys and girls is larger. Rarest of all are families in which the children are all of the same sex; and among these, again, the most unusual are those consisting of boys only.

This distribution of the sex-combination is believed by Geissler to depend upon the fact that in the first birth and all the subsequent births there is generally speaking a slight advantage in favour of the male sex. It has not been proved that the sex of the first-born exercises a determining influence on the sex of the subsequent children. It does, however, seem clear that in the case of parents who have given birth in succession to several children of one sex only, there exists some definite obstacle to the procreation of children of the opposite sex. Putting these exceptions out of consideration, there seems to exist a tendency in the later births of a series toward the procreation, more especially of that sex which has been absent or deficient in the earlier births of the series. The strength of this equalizing tendency increases as soon as it has for the first time manifest itself. It is always greater when the sex deficient in the earlier births of the series has been the male.

I have myself undertaken a statistical investigation of the births occurring in the reigning families of Europe and in the families of the leading members of the aristocracy. The necessary particulars are to be obtained from the genealogical court calendars; and it is my belief that the data obtained regarding these uppermost strata of society are comparatively free from many sources of error by which the ordinary statistics of the subject are apt to be invalidated. For 556 marriages there were 1,972 births, comprising 1,023 boys and 949 girls, and thus exhibiting a sexual ratio of 107.7.

In relation to the relative ages of the parents, the following table was drawn up:

From these figures we may deduce the following conclusions, which are not wholly concordant with the law of Hofacker and Sadler: When the husband is older than the wife the excess of male births among the offspring is greater than it is in the case of an average drawn from the offspring of all marriages (in my cases the difference was 111.8 as compared with 107.7). But a closer analysis shows the difference to be less simple than at first sight appears. If the husband is older than the wife by one to five years, the excess of male births among their offspring (103.8) is less than in the average of all marriages (107.7); the same is true of the offspring of marriages in which the husband is more than five and less than ten years older than the wife, though the difference here is very trifling (106.8 as compared with 107.7). It is not till we come to the offspring of marriages in which the husband is from ten to fifteen years older than the wife that the increase in the excess of male births becomes notable (113.7 as compared with 107.7); and when the husband is more than fifteen years older than the wife the excess of males is higher still (122.1).

If we arrange these data so as to show, in cases in which the husband is older than the wife, the additional influence of the absolute age of the wife, we obtain results which partially conflict with those of Bidder, as follows:

Thus we see that when the wife is very young, i e., less than twenty years of age, even though the husband is older than the wife, there is among their offspring no excess of male births, but the contrary—a sexual ratio of 97.6 only. Most marked is the excess of boys in cases in which the husband is older than the wife, and the age of the wife is from twenty to twenty-five years. When the husband is older than the wife, and the wife’s age lies between twenty-five and thirty-two years, the excess of male births is not so great, though still considerable.

Hence it appears that the law of Hofacker and Sadler, which cannot be regarded as fully valid in the terms in which it was originally expressed, must be modified as follows: If the husband is at least 10 years older than the wife, and the latter is at an age when her reproductive capacity is at its maximum (twenty to twenty-five years), the offspring exhibit a notable excess of male births. There is still a considerable excess of male births in the offspring of marriages in which the husband is at least ten years older than the wife, and the wife is more than twenty-five years of age. On the other hand fewer boys are born than girls as the offspring of marriages in which, although the husband is older than the wife, the wife has not yet attained the age of maximum reproductive capacity—i. e., is less than twenty years of age. The excess of female births is most marked when the husband and wife are of the same age. When the wife is older than the husband there is a moderate excess of male births.

I admit, however, that the figures upon which I have based these conclusions are, like those of Hofacker, too few in number for the foundation of trustworthy inferences. The instances in my computation number 1,972; those in that of Hofacker, 1,996; but, as I have already remarked, there are reasons for believing that the data I have employed admit of the introduction of fewer sources of error.

The influence of the absolute age of the mother in the determination of sex having been statistically proved, many have inferred that this determination is not effected during the instant of fertilization, but occurs at a later stage of intra-uterine life, and is influenced by the manner in which the embryo is nourished by the maternal organism. It is suggested that elderly and immature mothers are unable to furnish the embryo with nutriment so well as those mothers who are at the age of maximum reproductive capacity, and that upon this fact depends the excess of male births in the latter case. (We shall return to this matter—the influence of deficient nutrition in relation to the excess of male births). But the proof of the fact that the absolute age of the father has also an influence in the determination of the sex of the offspring offers a ground for opposing this assumption that the sex of the embryo is determined during intra-uterine life subsequent to fertilization, and suggests that the father also exercises a determining influence in the origination of sex during the act of fertilization.

The absolute age of the husband seems also to have some influence upon the sexual ratio. The absolute age, like the relative age, of the father appears favourable to the procreation of a greater excess of boys. Thus, Hofacker found in 1,193 cases, in which the age of the father was from twenty-four to thirty-six years, that the sexual ratio was 100; in 683 cases in which the age of the father was from thirty-six to forty-eight years, the sexual ratio was 114; and in 105 cases, in which the age of the father was from forty-eight to sixty years, the sexual ratio was 169.

In investigations based upon larger collections of cases Schumann and Düsing have endeavoured to determine the variation in the sexual ratio according to the absolute age of the father.

Düsing examined the statistics of births in Norway, Alsace-Lorraine and Berlin, and from the data thus obtained he compiled the following table:

In this table we find the births arranged in relation to varying ages of the fathers and in relation to mothers whose ages are tabulated in three classes, the ages of the latter being those at which they are most prolific. The table shows clearly that the excess of boys is larger at the beginning and at the end of each column. Thus, the age of the mother remaining constant, young fathers and elderly fathers procreate a larger proportion of boys than do fathers of intermediate age.

But I find in this table, which is based upon a very large number of instances indeed, a confirmation of the thesis which I stated above, for the highest sexual ratio of 113.8 is in this table found in the case of fathers over forty-five years of age who are married to mothers of ages twenty-five to thirty years; this is, as I said, the case in which “the husband is at least ten years older than the wife, and the latter is at the age at which her reproductive capacity is at its maximum.”