CHAPTER I

SCHENK’S THEORY

THE

DETERMINATION OF SEX

BY

DR. LEOPOLD SCHENK

Professor at the Imperial and Royal University, and Director of the

Embryological Institute in Vienna

_AUTHORIZED TRANSLATION_

THE WERNER COMPANY

CHICAGO AKRON, OHIO NEW YORK

1898

Copyrighted, 1898,

BY

THE WERNER COMPANY

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PREFACE

The facts observed and recorded by others assisted me to advance so

far on the trodden path that I made an effort to snatch a secret from

Nature.

What I succeeded in obtaining, though small, induced me to set forth in

the following pages the perhaps not unimportant results.

The labor was long, and engaged my attention for years. And yet, amidst

my continuous labors in the province of Embryology, it remained all the

time a matter of secondary importance, my principal attention being

engaged by far more extensive studies.

My desire is to stimulate others to wider observation. May the facts

which I here discuss prove of utility, and encourage further studies

in this direction with the assistance of modern science.

If we are not in a position to control the processes of Nature, we can

nevertheless exercise over them a more or less effective influence, so

as to obtain such results as are possible.

Whatsoever the question may be that we propose to discuss, it is

sometimes very difficult to reach any answer. And yet, when experience

and diligence have helped us over the difficulties, we succeed at last

in reaching the answer desired. The difficulties assume much less

formidable shapes when an individual is satisfied with shaking his

head and regarding the whole affair with mistrust. In that way the

inexperienced and lazy are at once able to launch their views without

further trouble. They believe or they disbelieve; and they like to have

their say. Any one can in this way easily win himself a place amongst

those who have written on a topic. The man who desires to obtain a

lasting place takes on his shoulders heavier responsibilities.

This book contains but a portion of the vast and wide-reaching

literature dealing with the subject in hand. That literature

extends back to the date of man’s earliest intellectual labors. The

observations that have been recorded by others are here followed by

methods of investigation, and by considerations which may serve to

elucidate the facts. In conclusion, a section has been dedicated to the

methods which I recommend for the artificial influencing of sex. Some

particular experiments are subjoined.

May my little book, then, go out into the world and make known my

views, which are founded exclusively upon facts.

CHAPTER I

In sexually differentiated individuals, the difference of sex is

already apparent in the embryonal state of existence, not only in

the exterior form, but also in the interior cellular rudiments which

subsequently form the genital organs. In both, the earliest forms are

of such a nature that, up to a certain period, it is impossible for

investigations conducted with the means at present at our disposal to

discover any distinction. Soon, however, after this, in such organisms

as have a distinction of sex, elementary male and female forms of

the organs of reproduction can be recognized developing themselves

in the embryo out of the substratum of formative elements. Some of

these remain in a rudimentary condition; others attain to complete

development.

These processes take place at a relatively early period. They do not

seem to make their first appearance, as phenomena of vitality, in the

course of the life-development of the cells of the ovum. But it is

not improbable that, from the very outset, the ovule has a capacity

to transfer (during the process of segmentation) to a corresponding

cell-substance (out of which the generative organs will be subsequently

developed) the force contained in the ovule, so that the cell-substance

may afterwards take up the office of providing for the preservation

of the species. The cells of the ovum derive this power from the

protoplasma of the ovum, and retain it in a rudimentary form for

one sex, whilst for the other they possess it in full measure. This

energy is contained in the ovule itself in an unknown condition. In

it lies the basis of the formation and development of the future sex.

In close connection with this property of the ovule, lies another

faculty, included in the ovule, namely, that the other different

elements proceeding from the cell-body of the ovum, starting from the

protoplasma of the ovum, are endowed with certain vital peculiarities,

according as they belong to the future male, or female, organisms.

It will be plain from this that the germ of the future sex must be

sought in the first cell-segmentation of an ovum. As soon as some

of the cells derived from the primary protoplasm of the ovum have

developed themselves into genital cells, the other elements which have

originated from the same ovum are in such a manner conditioned that,

in the latter stages of their vitality, they adapt themselves, and, in

short, adapt the properties inherent in all the cells, to the sex of

the individual. According, as the ovum is male or female, so are also

the cells which originate from it either all male or all female.

It will be seen that not only do different cells for the different

sexes develop themselves out of an ovum, but that also, at the same

time with these, a peculiarity reveals itself in the other cells,

in accordance with which the sexually different organisms exhibit a

difference in their vital capacities, and take also different forms.

The distinction between male and female characteristics appears to

be determined before the fecundation of the ovum. The formation of

the ova in the ovary, and their further development, seem, however,

not to be independent of external influences. It is possible that

upon these circumstances depend the number of ova contained in the

ovary. But, apart from the question of quantity, it is possible that

many characteristics might so affect the quality of the ovum, as to

exercise an influence over its capacity for fecundation. We may here

mention an experiment which was made with the ova of a rabbit, from

which it was quite clear that the capacity of an ovum for fecundation

was immediately diminished when the surrounding elements attached

to the ovule, in consequence of the density of their investing

substance, offered a resistance to penetration by the spermatozoa.

(Schenk.) The penetration of a spermatozoon into the protoplasm of

the ovum becomes possible only when, in consequence of the movements

of the spermatozoon, the cells of the surface of the ovum can be

thrust aside. This is facilitated when the investing substance is

considerably relaxed, as is the case when the ovum is ripe. Other

circumstances, also, which can in some cases be easily detected, may

prove detrimental to fecundation and development. Indeed, they can even

exercise an influence over the sex which is to be developed out of the

ovum. Bee-masters (F. Gerstung) have frequently shown that the food

exercises a striking influence upon the formation of sex in the ova.

(v. Berlepsch.)

All evidence goes to support the view that such external influences

as would favorably affect the separate sexual individual might also

promote the production of one sex or the other. In Hensen’s valuable

work on generation, a number of instances are adduced, gathered from

various authors, which make it clear that the nutrition of the parents,

apart from any question of race, is capable of exercising an influence

upon the sex of the children. (Ploss.) In plants which produce separate

male and female blossoms (Lenkhart), the male blossoms are more

numerous when the temperature is relatively high, whilst in shaded

places and damp soils a greater number of female individuals will be

observed.

* * * * *

Facts which might assist to explain the origin of sex have been

sought after from very early times, and have been also placed in very

different lights. The result on every occasion, when this subject

has been discussed, has been always a wide difference of opinion.

People have, in consequence, been induced to fall back upon theories

of different sorts, theories which have for varying periods, sometimes

long, sometimes short, been accepted as of some assistance towards a

scientific explanation. In all the theories which have been propounded,

the sex has been regarded as already determined in the ovum, or else

the origin of the sex has been assigned to some early stage of the

development.

The earliest statements extend back into the ages of myth and fable, in

consequence of which any exact comparison of them is not an easy task.

All the different manuals which deal with the present question touch

upon these early views, and for this reason I am unwilling entirely

to ignore them here. I shall, accordingly, select a few of the more

important for mention.

The reproductive glands of the two sexes were supposed to contain

generative matter distributed in such a way, on the right and left,

that the right ovary and the right testicle contained the generative

secretions for the production of the males, and the left ovary and

left testicle those which produced females. It is immediately evident

that, according to this theory, it was impossible to exercise any

influence over the sex of the future individual. This primitive theory

is ever cropping up anew, always to be again rejected. Of various

other theories of the same kind, only those deserve any attention

which rest upon some basis of fact. Accordingly, recourse has been

had to statistics, and an attempt has been made to reach, from the

figures which they furnish, some certainty respecting which sex was

the more numerous, and what should be concluded to be the cause of

the greater prevalence of the one sex or the other. The fact was,

however, apparently overlooked that the available statistics, though

in many respects of the highest scientific value, could be of

real significance only when the numbers were gathered from widely

distributed peoples amongst whom there was none of that wandering about

the world which characterizes modern society.

I am at the same time unwilling to omit data, resting upon numbers

which have been gathered from statistics, and are not without value for

the determination of many important questions.

Ploss has in this way shown that in favorable years, when food was

cheap, the births showed an excess of girls. Under unfavorable

circumstances, more male individuals were born.

A comparison of statistics, however, soon led to another theory, which

culminated in this result, that in all countries an excess of male

individuals was born.

To what extent this relation between the numbers of the sexes can be

maintained, and may serve for a fixed rule, is at the same time a

question to be regarded with caution. An unimpeachable result of such

investigations is rendered more unlikely by the fact that comparisons

of numbers lead to a conclusion of an exactly contrary nature, making

the feminine sex the more numerous. These facts at once suggest that we

are not dealing with fixed or normally recurring numerical proportions,

which would repeat themselves at each numeration. And it is also

possible that external influences may in various ways affect such

numerical proportions.

We may add also that, in investigations of this kind, other circumstances

should be taken into consideration. Thus, in the case of endemic or

epidemic disease, the births which furnish the statistics fluctuate,

and the stability of the numbers, in consequence, is modified by these

exceptional occurrences.

The numbers (Oesterlen) which are based upon the population of half

Europe, are amongst the widest of statistical data, and furnish

information of the highest value.

They represent 59,350,000 births. These showed an excess of male

births. The proportions were 106.3 boys to 100 girls. Of course,

these numbers refer to the new-born, and must necessarily be very

much altered by the age of puberty. In fact, the powerful influences

which come into play in the life after birth would very considerably

affect the former of the above numbers. This is, however, a matter

for further statistical investigation, and of little importance in

our present inquiry. The numbers (Oesterlen) are in this respect very

remarkable: the average of the total number of births in the various

states corresponds very nearly with the numbers in the several states,

or at least shows no difference worthy of consideration. In the single

states, the proportion of boys to 100 girls varied from 105.2 to 107.2.

Thus the proportion of the number of male individuals born to the

number of females very nearly corresponded with the proportion shown

by the total of all countries enumerated. Statistics derived from the

genealogies of Court calendars gave (according to Kisch) 107.7 boys to

100 girls.

I am prompted here to quote also the statistical numbers given in

Hensen’s work, which have been taken from Darwin’s ‘Descent of Man.’ Of

pigs, rabbits, and pigeons, more males are born than females. For every

100 mares, 99.4 horses are born. In the case of greyhounds, 110 dogs

are born for every 100 bitches. Of horned cattle 94.4 males, of poultry

94.7 males are born for every 100 females. The degree of accuracy and

the limits of error which here remain undefined, make fluctuations

easily perceptible. The mistakes, also, which may be made in such

cases, are not always the same.

Statistics have been in many other ways called in to assist in the

discussion of the question before us. In the early decades of the

present century a question was raised--what was the effect upon the

relative number of births of male or female individuals when the

parents were of like or unlike ages?

Hofacker, in the year 1828, and Sadler (an Englishman), in the year

1830, attempted to solve this problem, and found adherents for their

theories based upon numerical returns. But the Frenchman, Girou (Paris,

1838), appeared as an opponent of their views, also supporting his

opinions by numbers obtained in the same manner, probably, as those of

Hofacker and Sadler.

I shall not here reproduce the tables which were constructed for the

discussion of this question. Any one who occupies himself with these

questions can refer to the respective technical works, and I shall

content myself with mentioning some of the results. If the man is older

than the woman, more boys will be born. According to Sadler, the

statistics showed even 121.4 boys for 100 girls.

If both the parents are of the same age, fewer boys than girls will be

born. According to Sadler, in this case for every 100 girls only 94.8

boys are born. But if the woman is older than the man, an excess of

girls in the family is the result. According to the two above-mentioned

authors, when the mother is older than the father the proportions are:

86.5 boys to 100 girls.

Similar numbers collected by other specialists differ not inconsiderably

from those given by Sadler. Regarding the proportions of male and female

births as affected by the respective ages of the parents, Sadler’s

numbers show the widest differences of all. Breslau and Noirot have

arrived at numerical results so different, though less than Sadler’s,

that no thoroughly reliable conclusions can be based upon them. Wall

confesses himself an adherent of this law, and lays down the principle

that in the intercourse of two quite young parents the male sex tends

to predominate. If, on the contrary, the age of the man is distinctly

greater than that of the woman, he insists on the excess of females

amongst the new-born. The French breeder Girou de Buzareingues is

disposed in many respects to support the theory of the influence of

difference of age in the parents upon sex of offspring; but, also, on

the strength of his own experiences in breeding, is partially opposed

to it. According to his theory, he also takes into consideration the

character, the food, etc., of the parents, and would have regard to

their size and strength. In this way he gave his theory a much wider

range. He mentions a great number of facts which he observed in the

human subject. He outlines the expenditure of force, mental and

physical, entailed on the parents by their occupation, and then sets

forth ten very precise particulars from which, in any given case, the

sex of the offspring which will result from the wedlock in question may

be known. The following cases from Girou may be mentioned. A vigorous

man married a corpulent, melancholy, elderly blonde. Seven daughters

were the result of the marriage, all of them resembling their father and

grandfather. Many similar cases are mentioned by Girou, all of which

may be found of interest to the reader, if he be inclined to regard

preponderance of temperament, or physical disposition for procreation

of the species as important factors. Included in his _repertoire_ of

anecdotes are many interesting and piquant details respecting the

results of the pairing of dissimilar temperaments which might be quoted,

were it not that this would lead us too far from our subject, and also

be of no service in the present inquiry.

Bidder is in many respects inclined to give his assent to the theories

of his predecessors, and states that women who bear their first child

between the ages of twenty and twenty-one produce more girls than boys

(Düsing). The older the woman is at the time of her first parturition,

the greater number of male births. An excess of male births will occur

in the case of those who first give birth to children between the

ages of thirty and forty (Eckhardt). Ahlfeld insists that this is a

universal rule in the case of women who become pregnant in later years.

A great number of specialists are of this opinion, and apply the data

afforded by statistics to support it in different ways.

The evidence of Stieda, Berner, and Birelli, and especially that of

Wilkens, respecting the domesticated mammals, leads, however, to this

conclusion, that the theories respecting the relative proportions of

male and female births set forth by Sadler and Hofacker must either be

given up or their value considerably discounted.

Specialists are also to be found who, in order to explain this theory,

have availed themselves of Darwin’s law, and in a certain measure the

results admit of this explanation.

The older parent, who evidently under such normal circumstances as

might be anticipated has a shorter time to live than the younger

individual, his consort, naturally in the struggle for life, makes

an effort for the preservation of his sex. Accordingly, the elderly

husband of a young wife, or _vice versâ_, the elderly wife of a young

husband, will make an effort to preserve the sex which is first

threatened with death, but which may at least be replaced by a majority

of births.

In so far as these theories are mere calculations and results which

have originated from comparisons of numbers (the numbers themselves

being in many cases of no practical value), the conclusions reached

may appear to be astonishing, and may be used to support either one

view or another, or to contradict them. Only one fact appears to be

certainly established, that, on an average, under normal circumstances,

the number of male individuals of our population that are born exceeds

the number of females. The difference amounts to a small and variable

number per cent., but in the case of the new-born, the excess is on the

side of the males. (Süssmilch.)

* * * * *

Thus far we have given such data as statistics have furnished. These,

it is true, belong principally to past epochs, and no new results of

this sort have been used by statisticians. But it would be equally

impossible to deduce from new statistics, or from old, or from both

together, any law of nature affecting the question before us.

* * * * *

I shall proceed next to examine the further theories on this subject

with which I have become acquainted from the perusal of the literature

treating of it. With some of the works which I am about to mention I

am acquainted at first hand. Others I know only from quotations found

in various technical publications. I have not attempted to arrange my

materials in any other way.

In the case of the most widely different branches of natural science,

and whether the author’s aim be descriptive or experimental, it is a

common practice to commence with a glimpse at what has been said by the

earliest writers. I shall begin in the same way. I shall, however, not

take into consideration what has been at various times mere folk-lore,

and is only traditionally known, but shall limit myself to such

traditions as have been preserved in writing. I have, besides, already

spoken above of suppositions respecting the origin of sex which appear

to partake of the nature of myths. To these it was impossible to attach

any importance. And the same must be said of other views which belong

to the epoch of the Greek or Latin writers on natural science, and are

so strange that they can be scarcely brought into any agreement with

modern knowledge.

In Ploss’s work ‘_Das Weib in der Natur and Völkerkunde_’ (Woman in

Nature and Popular Tradition), are to be found the various speculations

of different races respecting the origin of sex. Much of this folk-lore

is of a distinctly surprising character, and calculated to afford

the reader considerable amusement. For example, in Servia, if a man

has a stye on his eyelid he comes to the conclusion that his aunt is

pregnant. If the stye is on the upper eyelid, the child will be a male,

if on the lower, a female.

Amongst the Asiatic races religious ceremonies, prayers, and similar

expedients are considered efficacious, and capable of influencing the

sex.

What question is there of the present day, respecting which we can

consult the literature of the ancients, that does not take us back

to the writings of Hippocrates, Aristotle, or Galen, or to those of

the old authors of those oriental races whom we regard as the earliest

cultivated peoples? Hippocrates held that to produce a male, the

generative material must be of a stronger quality. The future destiny

of the male rendered it necessary that it should be constructed on

a stouter foundation. He must be capable of a stronger development,

and must, therefore, be a product of stronger elements alike on the

father’s and the mother’s side. A second hypothesis was soon added to

this primary one, but without any foundation of facts.

According to Aristotle, the woman supplied the primary material for

the development of the future individual. It was the function of the

man to give the impulse, in consequence of which the future individual

came into being. Next followed the purely mythical theory, already

mentioned, in which Anaxagoras believed. The much-sought-for origin of

the future difference of sex in the various individuals was assigned to

the right or left side of the organism. And Galen even concluded that

the right side of the body was the warmer, and the left the colder,

further claiming for the warmer side the privilege of producing male

individuals.

* * * * *

Various notions respecting the origin of sex have been also accommodated

to these primitive theories of the ancients, without resting upon any

positive foundation. No evidence exists to show from whom they

originated, nor how they were disseminated. Nevertheless, the historical

connection of these speculations justifies a reference to them, and

various hypotheses of this kind will be found in a little publication of

Dr. Heinrich Janke’s (Stuttgart, 1896). The older literature on the

subject of the generation of the sexes has been collected by His.

(_Archiv für Anthropologie, Vol. IV. V._) In ‘_Das Weib in der Natur

and Völkerkunde_’ (Leipzig), Ploss has collected ample information

concerning both ancient and modern ideas on this subject amongst the

different races of mankind. The procreative elements, furnished by the

male and female organs, after their mixture, compete with each other, by

virtue of their inherent forces, for the mastery. In this conflict, if

the male molecules are the more numerous, a male results. On the

contrary, if the female molecules are more numerous, the result is a

female. Nicholaus Venette ascribes the difference of sex to the

earliest phases of the life of the ovule.

* * * * *

The following aspect of the origin of sex is not without interest,

although the theory rests on somewhat insufficient foundations, and

is applicable, in the first instance, only to those creatures which

produce but a single individual at a birth. Many creatures, and

especially certain species of birds, present this phenomenon; they lay

in a single month two eggs. Of these, one is male, the other female. In

this way a provision is made for the equal increase, in each respective

month, of both sexes. In the case of man, it would, in accordance with

this, be anticipated that naturally an equal number of ova of either

sex would be produced by a single individual.

This would lead to the supposition that, in the case of the human

female, in one month a male ovule would reach its perfect development,

and in the next month, anterior to the occurrence of the menses, a

female ovule. Thus the ovary of the human female would contain in one

month a male ovum capable of fecundation, and in the following month

a similar female ovum. After a woman had once given birth to a child

it would then be possible to form a correct idea of the distribution

of the ova of the different sexes. The month of birth and the sex of

the new-born child would be known, and starting from the datum that it

would be the turn of the ovum of the next month to develop the opposite

sex, it would be possible to fix the given month in which an individual

of the male or female sex should be developed. (Dupuys.)

To these less general explanations of the origin of sex belong certain

very startling theories dealing with the question before us. These

notions are set forth at great length in theoretical explanations put

in the shape of popular expositions. According to these views a single

cell of the male or female reproductive glands is regarded as a sort of

complicated compound structure that might be compared to a spherical

world, in which thousands of primal individuals are contained, from

whose powerful and secret activity results the formation of male or

female individuals. (Hinz. Neusalz am Oder, 1897.)

* * * * *

Another very common opinion is that the seasons (Düsing), the climate,

and other local circumstances, have an effect in determining the sex of

the embryo. If the data supplied by Birelli, Berner, C. F. Vilson, and

Felkin, and many other authors, be taken together, it appears that the

different zones of the earth’s surface are not without influence in the

reproduction of one sex rather than the other. More boys appear to be

born in the north; in the warmer south more girls.

Felkin and Vilson adduce the following instance from the south of

Egypt:--The Wagandas, a warlike race, kill the men and the old women

of their conquered foes. The children, girls, and young women they

lead into captivity. On one occasion 480 of the women gave birth to

children on their march. Of the new-born 79 were boys, 403 girls.

This incident led the author to pay further attention to the subject

on the east coast of Africa and in the Soudan. Everywhere he found the

anticipation of an excess of girls supported and confirmed. In fact his

investigations of the phenomenon led him to formulate and advocate a

law that the better nourished and superior parent tends to produce the

opposite sex.

In this case the women are in an inferior position, and in consequence

worse nourished and practically exhausted. Amongst other neighboring

races, where they live peaceably and domestically, the difference

between the number of new-born boys and girls is not a very great one,

although a small average appears in favor of the girls. The influence

of different phases of the moon has also been taken into consideration,

and has been described as so effective that some have even attempted to

prognosticate by these means the sex of a second child after the birth

of a first. (Lioy.)

* * * * *

From Vilson’s statement that the sex of the worse-fed parent

perpetuates itself, a theory has been deduced which has been described

as _cross-heredity of sex_ (_Gekreuzte Geschlechtsvererbung_). In

accordance with this theory a prominent phenomenon would be that the

individual parents were not in a position to propagate their own sex,

but were yet under certain circumstances capable of reproducing the

opposite sex. If the father were the stronger, a girl would result from

the next impregnation; in the opposite case, a boy. A great number of

authors of renown, most of whom are mentioned in works dealing with

these questions, are supporters of this theory.

* * * * *

We have already mentioned that there are some who regard the act of

generation as a conflict in consequence of which the sex of the elder

parent, whether father or mother, will be reproduced, so that the sex

in question may maintain its position. Similarly, in the case of the

so-called cross-heredity of sex there seems to be a conflict for the

preservation of the opposite sex. What conception we are to form of

this conflict seems a difficult question. Any measure of the greater

or less excitability of the centers during the act of generation

(which might be determined in the case of animals) is not easily to be

reached with any degree of probable correctness; and how much less any

numerical index which would express the differences of excitability, of

strength, and so forth, which might be developed during the conflict

of the opposite sexes. The theory of the cross-heredity of sex rests

upon the phenomenon that those female animals which are impregnated by

sexually inferior and older males, whose capacity for reproduction must

be considered as inferior to that of the females, produce more male

than female individuals.

* * * * *

When a queen-bee lays male eggs, it is often asserted that these are

not yet fecundated. It is only after they have been impregnated by the

male that the female individuals appear. That is to say, after the male

influence has had its effect, the causes which lead to the development

of the female make themselves apparent, in accordance with the theory

of the cross-heredity of sex. Previously, this influence was wanting,

and, in consequence, only male individuals resulted from the eggs.

From the unfructified eggs of Daphnia (water-flea) many individuals

are at once developed, and in numbers so great as to be surprising.

According to Heincke, female individuals can be developed from eggs

which have not been fructified, but have been well nourished.

Dr. Clarke, a medical man of Detroit, is of opinion that in the

commixture of the elements, which serve as the basis of the future

individual, some external force is also embodied. Then the situation

would be something like this: there are two elemental forms, which, in

impregnation, are brought near each other, and their union actually

effected; of these the female ovum has the function of occasioning a

male offspring, and the male element that of occasioning a female.

In this act a conflict is supposed to take place, in which each sex

strives for the production of the opposite sex. But here there would

be also an expenditure of force on behalf of its own sex. This appears

to be a labor of love on the part of the sexually more ardent consort,

to which he or she finds himself or herself prompted by nature for the

sake of the weaker female or male sex, but at the same time without

any conscious volition of accomplishing an expenditure of power or

energy in this (reflex) act. Richarz affirms that it is the function

of the man to produce a higher degree of organization during the

development in the germ. But if the productive force of the mother is

more energetic, and exerts a greater influence, the result is a boy.

When, on the contrary, the generative force excited in the mother by

successful fecundation is weaker, the fecundated germ does not attain

the masculine sex.

Cases from married life are mentioned by different authors in which

the husband, partly in consequence of sexual debility, occasioned by

repeated seminal emissions on previous occasions, partly in consequence

of advanced age, and besides, also, through spermatic secretion

(_Samensecretion_), was scarcely capable of performing his conjugal

duties, nevertheless, pregnancy ensued, which after nine months

resulted in the birth of a boy. In these cases the mother would have

decided the sex of the child. But one is more inclined to explain

the origin and development of a boy in these cases by the law of

cross-heredity of sex. It may certainly be concluded from these cases

that a man, from whom it might have been supposed that no procreative

substance was to be had, although he can be reckoned amongst the

patriarchs of his species, may yet sometimes be able to boast that he

has left male offspring to be his direct heir.

On the other hand, Guttceit relates that a man, during the period

anterior to his having a mistress, and whilst he was entirely at the

service of his wife, begot only daughters. When, however, he limited

the time which he spent with his wife by devoting a part to a mistress,

his wife presented him with male offspring. This is a case which might

be explained by the law of cross-heredity of sex.

Serious surgical interference with the female certainly has an effect

upon fecundation. At least, pregnancy appears to be postponed after

the more difficult operations. If, however, impregnation takes place,

either male or female offspring may be anticipated. This contradicts

the theory of cross-heredity of sex, according to which only

individuals of one sex should appear, if one ovary has been removed.

Facts which have been brought to light by experiments with animals,

and by observation in the human subject, tend to give the theory of

cross-heredity of sex a higher value. But under the same circumstances,

other phenomena present themselves to observation which appear to

render some of the postulates of this theory untenable. Various

diseases which are diagnosed by medical men as organic disorders, but

which do not interfere with the power of reproduction, are apparently

without influence on the sex of the offspring, and also without

influence upon a striking prevalence of one or the other sex.

Richarz assigns all the power to the fecundated female individual. He

thus raises the culminating point of the female power of reproduction

to a height above that which other specialists will allow. In this

he is in complete disagreement with Roth, to whom he is also opposed

in other directions. Within certain individual limits (amongst which

is not to be included a diminution of capacity in consequence of

the necessary periodical functional impulses), the female organism

discharges its functions the more frequently and the more perfectly

the less often it is called into operation, and, _e contra_, the less

frequently and the less perfectly the more often it is called into

operation. According to Vernich, very long intervals between successive

pregnancies disturb the progressive increase in the weight of the

children less than very short ones.

One may, without being afraid of making any great mistake, at any rate

in the case of women who bear many children, make the same assertion

respecting the constantly increasing probability of male offspring, as

respecting the increase of weight.

The beneficial effect of a fairly long fallow season upon these

periodically acting organs is revealed in this way among others,

that, often enough, in consequence of prolonged rest and recovery of

strength, the female generative organs, after frequent still births,

became capable of producing healthy children. (Richarz.)

The fundamental law of crossing is supported by this author in every

direction. He recommends it as revivifying the blood and tissues,

in order to combat the evil effects of inbreeding, the exhaustion

of normal and healthy conditions, and as a preventative against the

appearance of degeneration and decay. A similar relation between the

sexes exists in their functions for the continuation of the species.

If an attempt be made (Richarz) to explain the different facts

observed, in accordance with the theory in question, no insuperable

contradictions will be met with. The general excess of male births,

their corresponding increase during the loss of many men in war (a loss

of distinctly stronger men), the high proportion of male births in the

case of mothers who produce their first-born at a comparatively late

age, the same high proportion where polygamy prevails, and, further,

the diminution of male births in the case of unmarried mothers, which

should not be overlooked,--all these phenomena are declared to be in

accord with Richarz’s views.

We will proceed here to give a brief sketch of Richarz’s opinion. Ribot

powerfully supports it in every particular from his own experience and

from historical data. The primary impulse upon which the whole process

of generation depends lies in the organs of the mother. Here lies also

the substratum in which is, as it were, the center of gravity of the

special generative process.

The function of the male sex is to evoke from the feminine substratum

an organism, or, more strictly speaking, to occasion a change in the

germ. If the mother’s generative capacity reaches the highest point the

result is a boy, who in external appearance resembles his mother.

If, however, it happens that the forces which act in the mother are

inferior to those of the father, the infant will be a female. She will

resemble her father, and will also inherit her father’s temperament.

Sex is not a transmissible attribute inherited directly from the

parents. Personal appearance and other characteristics will on the

whole correspond rather more with one of the parents than with the

other. Yet in every case the influence of the other parent will make

itself felt, and will in many respects exercise a modifying influence

over external appearance and other characteristics.

These views have been attacked by Roth, who declares himself against

Richarz’s hypotheses. His objections are contained in a work entitled

‘The Phenomena of Heredity’ (_Ueber die Thatsachen der Vererbung_). He

directly attacks the theory of cross-heredity of sex, and according to

his theory claims for each parent an equal share in the formation of

the future individual, at least in the earliest stages. Fecundation,

according to Roth, would at once be effective in determining the sex of

the future individual.

We shall have occasion hereafter to speak of the observations which

Mayerhofer has made upon the origin of sex. Here we shall mention only

a single fact. This is a result of his experiments with animals, and

seems to have a relation to the theory of cross-heredity of sex.

Ewes impregnated by a powerful ram bear more males than females, so

long as the ram is in possession of his full forces. After a time the

ram has to perform his functions repeatedly during a few days, as great

numbers of the ewes are rutting. The fatigued or exhausted ram then

begets only females.

Next the number of rutting ewes diminishes. The ram gradually recovers

his strength. Whilst constantly employing it with the remaining rutting

ewes he again begets male individuals. Now, according to the rule of

cross-heredity of sex, the number of females ought to be greatest at

the outset, because we here have a male of exceptional force. When the

ram is exhausted, according to the theory of cross sexual heredity the

males ought to be more numerous. It appears, therefore, that in this

experiment of Mayerhofer’s we have something which remains in want of

explanation. We shall presently have occasion to speak more fully of

the facts which this author communicates respecting the origin of sex

in man, and will then return to this subject.

The information which we have concerning a stallion (Sir Hercules)

belonging to the stud of Count Lehndorff deserves attention. This

stallion was twenty-six years old, and had to cover twenty-three mares.

The result was twenty-four foals of the male sex. This case of the

ardent mares and the old stallion can be explained by the theory of

cross-heredity of sex.

Particular attention should be here directed to a phenomenon which

seems to imply that a sexually exhausted individual always has

his advantage of propagating his own sex secured. It is a sort of

fulfilment of duty on the part of a strong female animal when her

litter shows a majority of male individuals, or male individuals

only. In this connection may be mentioned the facts communicated by

Settegast, Nathusius-Hundisburg, and De la Tellais, who arrived at

their results from experiments upon the proportions of the sexes of

the offspring of the domesticated mammalia.

* * * * *

Attempts to solve the problem of the origin of difference of sex by

means of experiments have been numerous. So early as the last century

Platz attempted to carry out experiments with living animals.

The temperaments of the breeding couple ought to be concordant. Both

should be either of warm or cool temperament. Warmth and moisture are

primary conditions of fertility, not in plants alone, but amongst the

animals also; and (as Mayoor Zsigmond, of Kaschau, proclaimed in 1723)

represent the primary conditions of the possibility of a conception.

The warm element belongs to the man; the moist to the woman. Where both

qualities are to be found in both, offspring may also be anticipated.

But if this be not the case, for example, if the man’s warmth does not

accord with that of his wife, but is of a higher degree, then he can

beget boys. If he be not so warm, he must, if he wishes for sons, make

a distinct alteration in his diet. According to the prescription given,

he ought to lead a regular life and to limit himself strictly to warm

and dry aliments. The temperament of the woman is often ardent and dry.

In this state it must be regarded as unfitted for the development of

an embryo. Befitting food would not be without an influence upon the

alteration of temperament. Respecting this, experiments had proved this

much, that a suitable change of diet can exercise a salutary influence

over the temperament. A woman who was in the highest degree beautiful

in face and in every part comely had a temperament which would accord

with that of any man.

Then comes the theory of the allotment of the male and female in man,

and in all the vertebrata, to the right and left sides of organs of

generation. This is a theory which is being always brought forward,

even by the most recent writers, some of whom go so far as actually to

wish to support it by experiments.

Thus the excision of one or the other of the testicles of the male

is recommended in order that the owner may be able to breed the sex

which he desires. It still remains, in order to effect the artificial

determination of the sex, that the female should also play her part

correctly, so that the semen of the male may be conveyed to an ovule

from the required ovary. An effort was accordingly made to secure

intercourse in such a manner that the semen of the male might be

delivered in a certain direction in agreement with the anatomical

position of the duct which was to lead the seed into the required

ovary. But it was practically difficult to settle what position in the

intercourse was the right one. Experience proved that in a certain

case on two successive occasions male individuals were born when

the impregnation had been so contrived that the semen should enter

the right ovary. Therefore the left ovary was for female offspring.

It is not our concern to enter into further explanations of these

occurrences. Only this much may be said, that experiments have been

constantly made which might lead to some conclusive solution of these

questions, without any result having been obtained.

* * * * *

A publication appeared in the year 1786 dealing with the above-mentioned

theory, and at the time attracted much attention. It has now become

difficult to procure, and is often mentioned on account of its containing

much that is valuable for influencing sex, both amongst men and animals,

that has been gathered from all the authors of the previous century, and

more especially from all the ancient authors who had written on this

subject.

The author was J. Ch. Hencke, organist at Hildesheim, and the title

of his book, ‘The Secret of Nature Completely Discovered, both in

the Procreation of Man, and for the absolute choice of the Sex of

Children.’ Brunswick, 1786. (_Völlig entdecktes Geheimniss der Natur,

sowohl in der Erzeugung des Menschen als auch in der willkürlichen Wahl

des Geschlechts der Kinder._ _Braunschweig, 1786._) The author relies

upon exploded theories, according to which the offspring is evolved,

as it were, out of a mixture of the generative secretions of the two

sexes, and can be induced to develop into either a male or female

individual. Thus the sex is not previously determined, only in the

course of its development out of the developing mass, which consists of

a mixture of male and female generative secretions, distinctive sexual

characteristics make their appearance, according to the predominance

of the male or female portion of the mixture. But here, also, the

old theory is set forth very precisely. The generative matter of the

right testicle serves to fructify ova from which males are developed,

that of the left testicle is used to fructify and develop female ova.

Similarly, the tenet is propounded that the right ovary contains male

ova and the left such only as will, when developed, produce female

offspring.

* * * * *

These doctrines, as a basis for the breeding of animals, Hencke had

discovered by castrating swine, dogs, and rabbits. Thus it happened

that a boar, who, after castration, had only the left testicle, twice

running bred with a sow female young only. Similar phenomena occurred

with other animals, so that this method was recommended by the author

to the breeders of his time. But it happened, also, that a surgeon

upon opening the body of a woman who had had sons only and never a

single daughter, found the left ovary very thin and withered, so that

it was hardly possible that it could serve for the development of

a new individual. On the contrary, the right ovary was in a normal

condition. It now remained only to discover some device for man,

by which he might be able, during the act of generation, to avail

himself of the discoveries thus made, so as to obtain the result of an

absolute choice of the sex of the offspring. The ligation of one of the

testicles was Hencke’s infallible remedy. When this severe proceeding

proved impracticable, in its place was substituted an elevation of

the testicle by means of its suspending muscle (the cremaster). Under

certain conditions this takes place of itself in particular positions,

and was accordingly recommended as an established proceeding for men.

One other conclusion of Hencke’s deserves particular mention. He was

bold enough not only to assert that the right and left sexual glands

served exclusively for the generation of male and female individuals,

respectively, but also asserted that the generative matter from the

right or left gland of one parent was productive only when united with

that of the same gland of the other parent. His counsels were not for

such persons as are too heated, too ardent. “For young, hot, hasty

men,” he says, “who are altogether without consideration, I am not

writing; but for chaste married people, and especially for those to

whom the production of a child of one or the other sex is a matter of

importance.”

* * * * *

Couteau established the fact that each seminal duct had its own

orifice, through which the semen was poured into the urethra. This

fact was in his days of the greatest importance, as it prevented any

mixture of the semen of a man’s two testicles. Hencke firmly insisted

that the semen was discharged by one testicle or seminal vesicle

alone, in the case when the testicle was raised up. But we need not

here follow further Hencke’s theories which he deduced from his own

experiments. In the present day these theories will satisfy no one.

Results which have been obtained either after ovariotomy, or after the

extirpation of testicles, have made us perfectly certain about the

value of one or the other generative gland for the production of the

male or female sex. The case of Schatz, which has been also pointed to

us as important in other specialist works, may not be uninteresting

here. The left ovary of a young girl was removed, together with a

portion of the left tube, and the right ovary, also, with the exception

of a margin of about two millimetres’ breadth. When she was married she

gave birth to a girl, whereas a boy should have been expected, seeing

that only male offspring were to be produced by the right ovary.

Scarcely any work that lies before us on this subject is so much

regarded as that of Hencke. At the same time, and although it had

in its day the widest circulation, it frequently met with the most

unqualified condemnation. Dr. von Seligson, in his discourse before the

Society of Medical Practitioners at Moscow (1895), on the subject of

influencing the development of sex, in connection with Hencke’s theory,

attached value to a great number of experiments tending to support the

old view. It was, however, admitted that by a departure of nature from

the ordinary law (somewhat resembling a transposition of the viscera)

male or female ova might occur in the respectively opposite ovaries.

* * * * *

De Bay, who was opposed to the theory of the anteriorly-developed

sexual products of the right and left ovaries, asserts that the

quality of the generative products depends upon the quantity of

nitrogen existing in the chemical composition of the ovum and the

semen. A large proportion of nitrogen in the ovum occasions the

development of a girl. If, on the contrary, the semen contains a great

quantity of nitrogen, a male individual will result. To determine the

proportion of nitrogen, or to give it scientific value in such cases,

seems to be a difficult matter.

* * * * *

Mention is also made of cases of tubal pregnancy in which the sex

was determined, and an effort has been made here, also, to find some

support for the theory of the existence of sex in the ovum whilst

in the ovary on the right or left side. Fourteen of these tubal

pregnancies, described by different authors, showed boys on the right

and girls on the left side. (Seligson.) In such anomalous cases where

the embryo has developed itself in the Fallopian tube, and has not

reached the uterine cavity, there is no doubt that the developed ovum

originated in the ovary of the side on which it was found.

Efforts are made to confute the different objections raised in many

quarters. The mention made by the traveler, Peter Kolben, of the

practice of cutting out one testicle, which is the custom of certain

African tribes (this is contradicted by Le Vaillant [1784], and by

Fritsch [1880]), and the accounts of Otto Finsch, may not deserve

credit, as they rest upon assertions made by other persons. Accounts

are further given, drawn from medical experience, of men who, after

prolonged orchitis, with consequent occlusion of the vas deferens,

begot only children of one sex, or in other cases were unable to induce

pregnancy. Also the discharge of semen was asserted not to take place

from both spermatic ducts at the same time. After many digressions,

Seligson in the end adheres to Hencke’s theory on no sufficient

grounds, and then bases on that theory a method, upon which I shall not

here pass judgment, but merely mention it without describing it.

At all events, there can be no question of a compression of the

spermatic cord in any way, for it could not be accomplished, either

manually or with the aid of various kinds of apparatus, without giving

rise to excessive pain.

In this case, as Hencke in his time explained, the cremaster muscle

raises the testicle up towards the inguinal canal. At complete erection

the testicle is drawn up and pressed against the inguinal ring. This

gives more favorable conditions for leading the semen forward from this

one of the two testicles; and this portion of the semen is used for

impregnation, to which end also a favorable attitude and a free passage

into the ovary must be provided. According to the views of the author,

this method, if adopted in procreation, will lead to the desired result

of producing a given sex. Exceptions are admitted. Exceptions occurred

in five families with twenty-three children. The author clings firmly

to his theory that each testicle possesses its own special spermatozoa

and each ovary its special ova, in which a given sex is already in

existence, and from which in fruitful intercourse male or female

individuals originate.

* * * * *

Next after a number of theories which have been current on this

subject, we reach some others, to which more or less value has been

attributed. Morello attached weight to the concentration of the semen.

Thin, liquid semen was to be favorable to the production of females;

thick semen produced males. According to modern theories, based upon

observation of invertebrate animals (O. Hertwig, Balfour, Landois,

Minot, and others), it appears improbable that this position can

be maintained. The supporters of this theory assert that a single

spermatozoon suffices for the fertilization of an ovule, or to develop

the ovum into a so-called “oosperm,” that is to say, to form a really

fertilized ovum. (Perhaps the excess of semen serves for the earliest

nutritive processes of the ovum; which would, however, be difficult to

prove.) This fact has been also confirmed in the case of the higher

animals, and it might be in a similar manner brought to an issue in the

case of man. However, observations of this kind have not yet proved

possible with man. But in the case when several spermatozoa penetrate

the interior of a single ovum, anomalies in the process of development

result from the formation of several nuclei. Such ova, also, perhaps in

consequence of excess of semen, are very often aborted and perish.

In order to throw light on the causes determining sex, Pflüger (in

connection with results obtained by Born, which will be cited

later) attempted to determine the relative numbers of the sexes,

under normal conditions, in the case of the frog (_Rana fusca_). The

numbers were taken by his pupils, A. von Griesheim and Dr. W. Kochs.

The identification of the sex was made with a microscope under the

supervision of Pflüger. According to Pflüger the Graafian follicles

are easily identified with the aid of a microscope, if they are not in

their earliest stage. They contain an ovum with a scanty yolk and large

germinal vesicles with germinal markings. The whole is surrounded by

connective tissue.

According to Pflüger, the epithelium is wanting in such very young

follicles. In these frogs after their metamorphosis the testicle

consists of tubes, with multinuclear epithelia, and is easily

distinguishable from the always large ovaries of the tadpoles. By

different concentrations of semen, Pflüger attempted to influence the

proportion between the male and female sexes.

According to Pflüger, there are normally found amongst frogs in a

state of nature 36.3 per cent. males, and 63.7 per cent. females. With

thinner or thicker semen, the average number can be altered. With thin

semen Pflüger obtained 27.3 males and 72.7 females per cent. With

concentrated semen he obtained 39.4 males, and 60.6 females. Pflüger

carried out some other experiments, and came to the conclusion that the

concentration of the semen or the extract from the testicles exercised

either a very small influence or no influence at all upon the sex.

When he took an average result from all his experiments, he found that

out of 806 frogs which he raised, 288 were males. Whilst the normal

proportion of the males developed freely under natural conditions was

36.3 per cent., that reached by experiment was 35.7 per cent. It should

be here remarked that among the tadpoles many are found whose sex is

not yet determined. They are in a hermaphrodite condition, out of which

they develop into either males or females.

* * * * *

Robin, the well-known French histologist, made the question of the

origin of sex the subject of an extensive inquiry. His investigations

start from the following point:--In warm climates the whole quantity of

blood in the inhabitants is less than in temperate zones. The process

of respiration in the inhabitants of warm climates is also not so free

as in the case of those who inhabit temperate or cold zones.

From this it would seem that some process connected with nutrition,

and with the passage of nourishment into the blood, is the cause of

the number of male births being greater in the cold zones than it is

in the temperate zones, or in the inhabited regions lying nearer

to the equator. It would follow from these considerations, that if

the women were subjected to such a régime as would materially affect

their respiration and the quality of their blood, more boys than

girls, or the contrary, might be bred. If so, breathing an atmosphere

containing more oxygen, with a corresponding diet, would be the right

receipt for producing in the woman such a basis that in the course

of development the male generative organs (which Robin considers the

anatomically more perfectly developed) might be evolved instead of the

female. According to Robin, the male sexual apparatus in comparison

with that of the female is provided with the more perfectly developed

character. Robin further insists that strong men will beget more male

individuals. Further, that a woman who indulges in sexual intercourse

somewhat seldom has female children; and that voluptuous women, who

are fruitful, generally bear boys. A number of experiments with

domesticated mammalia are adduced in support of this view.

* * * * *

Hegar teaches that in the case of a merely rudimentary development of

the germinal gland either sex is developed.

With the views of Robin may be connected also other suggestions

regarding the food of the parents. These have been tried both with men

and animals. But we shall not here go further into them. Nor shall we

mention the different kinds of food or drink which have been employed,

whether by men or women, to produce a greater sexual activity.

* * * * *

The eminent naturalist Born, of Breslau, made a long series of

experiments, which are of the highest interest in reference to the

doctrine of the origin of sex. It is easy to fertilize frogs’ eggs

artificially. The ripe eggs are taken directly from the female,

and the testicles of the male rubbed with water. This fluid, which

now contains spermatozoa, serves to fertilize the eggs. Spallenzani

had already undertaken artificial fructification. Born observed,

during his study of the course of development, that the effect of his

breeding as regarded sex was to produce 95 per cent. of females. This

number is evidently so remarkable that it ought to secure particular

attention. No such extreme contrast between the numbers of males and

females is to be found amongst the frogs that develop freely under

natural circumstances. It seemed to Born that his result was to be

referred to insufficient nourishment, and that the tadpoles, being

somewhat unfavorably circumstanced, had not been able to attain the

development of the stronger sex. In this experiment on the evolution

of sex it appeared that not only was there an excessive production

of females, but that the other organs of the embryo and its whole

constitution could be modified by means of nutrition. It is also to

be observed respecting this most interesting experiment that many of

the tadpoles perished of hunger. Now, the number of still-born males

of the human species very much exceeds the number of still-born girls.

The mortality amongst males is so great that the average is from 136

to 140 still-born boys to 100 still-born girls. An attempt has been

made (Pflüger) to explain this phenomenon in the human subject on the

ground that the tenacity of life in the female sex in the period of

embryonal existence exceeded that of the male. Consequently, boys would

more easily perish during development than girls. If this observation

made with respect to human beings were applied to the tadpoles, it

might also explain the high percentage which the females showed among

the frogs. Very likely the male tadpoles possessed less capacity of

resistance; or, in other words, were less tenacious of life than the

females. It will be understood that this view would apply only as a

partial explanation of the facts set forth by Born.

* * * * *

In the artificial breeding of trout, which is conducted under cover, in

which process the embryos which have crept out of the ovarian follicle

are kept with the yolk-sacs in small reservoirs under a continuous flow

of water, it is observed that single individuals develop themselves

further. They lose their store of yolk with the yolk-sacs. In the

course of their further development and nutrition they arrive only

very slowly at the development of the internal generative organs. Even

in a very advanced stage the sex is not yet so plainly indicated as

in fish of the same size living free. Indeed, it is even affirmed by

many persons of experience that in the artificial breeding of trout

even those that have attained their full growth remain unfruitful and

cannot be used for further breeding. (D’Audeville and Arens raised, in

the case of trout, more females by dry impregnation.)

* * * * *

Here might be adduced also many other doctrines of greater or less

interest respecting the theory of the origin of sexual distinction.

Only in order that I may not introduce too much literary matter, I

shall mention only a few of the more important and noticeable theories

before I return once more to the experiments upon the influence of food

upon the development of sex. Janke’s work (small edition), published at

Stuttgart in 1896, furnishes a synopsis of the literary work done, as

do other books which treat of this subject.

* * * * *

Mons. Thury, professor at Geneva, published at Leipzig, in the year

1863, a book on the law of breeding the sexes, which, on account of

its contents, attracted great attention. In this work the author, after

a number of successful experiments and other investigations, shows how

an influence may be exerted over the sex of plants, animals, and men.

This work stirred me up to the endeavor to devote myself to this

question, so far as that might be possible. I shall give a short sketch

of Thury’s work, together with the critical revision of it by Dr. H. A.

Pagenstecher, of Heidelberg.

The doctrine respecting the origin of sex in cattle was laid down by

Thury from his own investigations. The principal point in his doctrine

of the origin of sex in animals he considers to be the condition of the

ovum at the time when it is fertilized. If the ovum has reached the

stage of ripeness, which may be described as an advanced stage, we may

expect to have, after fertilization has taken place, a male individual,

which will develop itself out of the ovum. If, however, the ovum

has reached only an imperfect state of ripeness when successful

impregnation takes place, then no such powerful and perfect specimen

of the race as the male is can be developed, and the result of such an

ovum is always a female.

* * * * *

From this it follows that, according to Thury, the cause of sex lies in

the ovum developing itself in the ovary, and the degree of its ripeness

is the only factor in the development of one sex or the other.

It is not, however, shown what the systems are by which such an ovum

can be correctly judged, so as to determine the different degrees of

ripeness. We now know very well certain signs which appear upon the

maturation of the ovum, of which we shall not say more here. Of these

Thury could know nothing in 1863, because at that time they had not

been discovered.

Thus the sex depends upon the ripeness of the female’s ovum at the

time of its fecundation. In the case of its having reached the highest

degree of ripeness, a male is the result. It is impossible for the ovum

to attain a higher degree of ripeness. If the ovum of a human female

has arrived at this supreme degree of ripeness, it has reached that

stage in which it is capable of becoming the basis of the most perfect

living creature which exists upon our globe.

Rutting is an external sign of the maturity of the ovum amongst the

lower animals. When, during the rutting period, an ovum is detached

from the ovary, and passes through the Fallopian tubes to the cavity

of the uterus, the fructification can take place at the beginning of

the rutting period. At this period its ripeness is not so far advanced.

The result of the development of such an ovum is a female. But when

the fecundation has taken place at the end of the rutting period, the

ovum has reached its highest degree of development, and, if effectively

fecundated, it will become a male. It follows that the signs of rutting

should be carefully studied, as in fact is habitually done by practical

farmers. The duration of the rutting period and the influences which

affect fertilization should be accurately known in order to lead to any

practical result.

Females at their first conception would usually produce, or would be

particularly disposed to produce, female individuals. Experiments

succeed better with such as have often produced young. In their case

the symptoms which indicate the commencement or the conclusion of

the rutting are much more easily determined, so that they are better

adapted for these experiments.

* * * * *

We know well that in the case of the lower animals when rutting, as

in the case of the human female during menstruation, an ovum is

liberated from the follicle in the ovary, and ordinarily passes away

in the menstrual discharge. In fact, a follicle of the ovary bursts,

and, to be precise, that one which protrudes most beyond the surface

of the ovary. This bursting of the follicle has not actually been

observed. But that this event takes place there can be no doubt, for

the locality of the fissure is perceptible, and the ovum is found

either at hand on the ovary, or else on the fimbria. The increase of

fluid in the follicle of the ovary, and the excessive charge of blood

in the vessels on the walls of the follicle, seem to be, without any

actual contraction taking place, the physiological causes of the

freeing of the ovum from the follicle, so that it may come in contact

with the semen. Ovulation can take place without intercourse. But

sexual intercourse can also favor ovulation; at least, it appears to

facilitate the separation of the ovum from the ovary.

Bischoff made known the fact of the separation of the ovum from the

follicle. He showed that the presence of sperm in the feminine organs

of generation of the animals was indifferent, that the rutting of the

animal was the index of the ripeness of the ovum. Eimer, Beneke, Van

Bamecke, and Hensen, call attention to the phenomenon which is observed

in the case of bats, who for a whole month before the detachment of the

ovum from the follicle have their uteri full of semen.

* * * * *

These processes which take place at rutting time are attended with

sexual excitement and congestion of the external genitals. It is not,

however, necessary that these processes should in the case of all

animals occur at the same time as ovulation. If rutting animals are

restrained from sexual intercourse, the sexual excitement of the female

passes off; but the symptoms of rutting again make their appearance

after a time. These are the phenomena of the so-called rutting season.

This rutting season lasts with sheep fourteen days, with swine

fifteen to eighteen days; with cows, horses, and apes four weeks. It

corresponds to the menstruation of the human female (Hensen). Many

bitches admit the dog only when six or seven days have elapsed since

the issue of blood. In the case of many animals rutting is marked by a

flow of blood from the genitals. This is the case with apes, bitches,

swine, and many other mammalia.

* * * * *

Under these circumstances, the symptoms of rutting are sufficiently

distinctly marked to make it possible, as Thury suggests, to determine

the advanced state of ripeness or its commencement in the ova. But it

is scarcely possible to say when the period of ripeness commenced in

this ovum or that. An ovum which had begun to ripen early may, at

the beginning of the rutting time, have attained to the condition of

a male-producing ovum. At the same time, others which are fertilized

at the conclusion of the rutting, but had begun to ripen comparatively

late, may, at the end of the rutting time, not yet have advanced far

enough to be able to develop male individuals.

* * * * *

Thury bases his doctrine on a number of phenomena of the vegetable and

animal world, and upon various experiences in the case of man. He also

adduces many statistical data in explanation and support of his theory.

The observations on plants make it indisputably clear that all the

circumstances which favor growth and ripening are favorable conditions

for the development of male organs. If all these circumstances are

lacking, female organs are produced.

Dark and cold, for instance, cause the male organs to perish. In

recent times a great number of extended studies of the phenomena of

vegetable life in this direction have appeared. I may mention more

particularly the following experiments made by M. von Treskow in

Gorlitz with _Arisæma_ (Verhandlungen des Botanischen Vereins der

Provinz Brandenburg, 1895). This plant first produces male flowers. In

the later year, when it has become larger, it produces female flowers.

The transition from the male flowers of the early stage to the female

flowers of the later stage can be hastened at pleasure by planting in

rich garden mold and manuring with horn shavings. If, on the other

hand, the plant be placed in poor, sandy soil, it reverts to the male

flowers. The same author quotes in his essay a remark of Heyer’s

(Halle, 1884), who declares that no sufficient observations exist

respecting the influence which different situations exert over sex.

I adduce this instance, for the sake of remarking respecting it, that

on this subject also controversies exist, which must be settled by

wider studies of the life of plants.

Cornaz has tried to derive from cows evidence in support of Thury’s

theory. He had twenty-nine cows impregnated with attention to the

rutting time, and from twenty-nine births received twenty-two females

and seven males. Cornaz attested his experiment by a declaration, and

the experiment was repeated in the French state domains.

But the experiment alone was striking enough to invite repetition. It

also met with partial success. But the plan was afterwards entirely

given up, perhaps in consequence of disappointments.

In this case it very likely happened--as in such experiments it very

easily may happen--that, in consequence of insufficient practical

knowledge on the part of the experimenter, the actual commencement

of the rutting time was overlooked. In addition, it is well known

that animals, in consequence even of an amount of exercise not very

exhausting, and in many other ways, as well as in consequence of the

food they have taken, may exhibit variations in the activity of their

rutting. It is not, therefore, surprising if the results of experiments

show much that was unexpected.

I here pass over a great number of proofs which Thury gives in his

essay. Funcke (1866) made in his ‘Physiology’ the following remarks

on Thury’s theory:--“Although the origin and determination of sex is

not indisputably proved to depend upon the degree of ripeness of the

ovum, it appears to me that we have not reached the right time for

determining the factor upon which it does depend. These experiments

have been made to repose upon a fact, which fact certainly proves,

beyond the possibility of dispute, a relation between the fertilization

of the ovum and the subsequent sex. This fact is that, in the case of

certain creatures capable of parthenogenesis (unisexual procreation),

we find that, from unfertilized ova one sex always results, and from

fertilized ova the other. But any closer interpretation of this

function of the semen is rendered nugatory in advance by this, that it

is in some cases the male and in others the female that results from

the unfertilized ova.”

* * * * *

Thury’s theory can be very suitably brought into agreement with the

theory of cross-heredity of sex, and explained by the assistance of

that view. The cow, at the beginning of her rutting, is not in a

condition of great sexual vigor. If the ovum be effectually fertilized,

it may be supposed that the bull, in procreative activity the superior

consort, will be fitted not to reproduce his own sex, but that of the

weaker cow. At the end of the rutting period the cow, which is brought

to the bull, has her ovum ripened to the highest possible degree, and

in consequence, when compared, from a sexual point of view, with the

bull, is distinctly the stronger and superior, and a male calf is in

this case the result of conception.

According to the theory of cross-heredity of sex, female creatures

should in the former instance be produced, and in the latter males,

which same result is reached in accordance with the theory of Thury.

Attempts have been also made to apply Thury’s theory to the human

species. The menstruation of women has been compared with the

rutting of the lower animals, and has been considered a protracted,

oft-repeated rutting. Now, as an ovum is specially developed every

month, it follows that this ovum requires a certain part of a month to

attain a more or less advanced degree of ripeness. According to this,

the ova which are fertilized a short time after menstruation will

develop only female individuals, whilst those which have had a longer

time in which to attain to ripeness would develop themselves into males.

The mucous membrane of the womb ought, about ten days before the

beginning of menstruation, to thicken itself distinctly in consequence

of a turgescence and dilatation of the vessels. In consequence it

appears swollen and loosened, and it has reached the culminating point

of swelling when the menstruation is at its highest. After menstruation

the swelling does not immediately decrease, but lasts on for about

nine days, until the mucous membrane returns to its normal condition.

(Hensen.) Thus it seems that the swelling and hyperæmia in the womb

appear at the same time as the conditions which lead to the ripening of

the ovum. The fertilization of the human ovum would be, therefore, most

efficacious at the time when the mucous membrane of the womb is also

most appropriately prepared, and it is probable that the same moment

is the one when all the other coincident factors are of a sort best

calculated for the reception, the fixing, and the protection of the

ovum. It is simultaneously with these processes in the mucous membrane

of the womb, and in the other parts of the generative organs of the

woman, that the ripening of the ovum is effected.

Now, it may appear not to be a matter of indifference (and may very

likely even have some connection with the development of sex) whether

the ovum is fertilized at a period during which the mucous membrane

is passing through its changes in order to reach its highest point of

swelling, or at the time, when, after menstruation, the mucous membrane

is, during so considerable a period (nine days), passing through a

retrograde metamorphosis in order to return to its normal condition.

This protracted process seems to correspond to the protracted rutting

in the form of a menstruation. If so, the human uterus, as Thury’s

theory would declare, would be prepared, to a certain extent, in

different ways, for the reception of the ovum, according to the

different sex-conditions of the future child.

* * * * *

It is not sufficiently known to how great an extent the principles of

Thury’s theory have hitherto found their right application to the case

of man. They seem in practice to be applied in different ways.

It seems that in cases where a result was obtained it could be more

easily explained by the principles which have been already described

under the theory of cross-heredity of sex. The assumption of a greater

or lesser degree of ripeness of the ovum which was to be developed was

a very questionable one.

The different processes with which we have become, in more recent

times, acquainted as symptoms of the ripening of the ovum, are not

here intended. Such symptoms can be observed both in the ova of

the invertebrata and in those of the vertebrata. These symptoms,

which are such as the attainment of the normal size of the ovum of

the species in question, the protrusion of the orientation points

(_Richtungskörperchen_), the steps towards the formation of a female

anterior nucleus (_Vorkern_), etc., do not here apply, for the

recognition of that higher degree of ripeness in the ovum which is

necessary at the time of fructification for the development of a male

individual.

All the above symptoms occur alike in the ova destined for the male and

for the female sex. That ripeness of the ovum upon which Thury’s theory

insists, lies in the nature of the ovum apart from any anatomical

signs. It is a condition of the ovum which we can only attempt to

explain by laying down the principle that an ovum which has been for a

longer time prepared in the female generative organs previously to its

fertilization, must be riper than another which has had less time for

this preliminary process.

* * * * *

We have mentioned above that on the occasion of Thury’s experiment,

the desired result was effected in twenty-nine cases. Pagenstecher,

Siebold, and Köll have dealt critically with Thury’s work. Coste was

not in a position to confirm these experiments, nor to verify them.

In order to test Thury’s results as applied to the human subject,

Schröder obtained the assistance of young women, who were in a position

to give him positive and accurate information respecting the time at

which they became pregnant. The women could name the day on which they

had had sexual intercourse, and knew the date of the last menses.

From careful calculation of the interval between these dates, it was

possible to ascertain approximately at what stage impregnation of the

ova took place, the degree of ripeness of the impregnated ova could

also be inferred from the space of time that had elapsed since the

last menstruation, and the sex of the fœtus was noted. Schröder found

that on an average of twenty-six cases in which boys were born, the

conception had taken place 10.08 days after menstruation; on an average

of twenty-nine cases in which girls were born, 9.76 days after. In

consequence, he was not able to confirm Thury’s theory in the case of

the human subject.

* * * * *

The experiments of Albini in Naples (according to Kronecker’s report

‘_Centralblatt für medicinische Wissenschaft_,’ 1868), which he made

during four years in his great poultry-yard showed in the first place

that hens for eight days after being separated from the cock laid none

but fertile eggs. On the ninth and tenth day the fertile and infertile

eggs were of equal number. On the twelfth day all the eggs were

infertile. Nevertheless fertile eggs appeared even on the eighteenth

day. It is possible that they had been impregnated by spermatozoa which

had remained in the folds of the mucous membrane of the uterus.

Hens never yet impregnated, or such as had not been impregnated for at

least a month, in three days (after impregnation) laid fertile eggs,

which increased in number daily.

According to Albini, hens can in Naples leave the eggs which they

are hatching. The shell can be partly broken off and again replaced

without the embryos necessarily perishing. But care must be taken that

no fungoid growth reaches the germ, as this is easily fatal to it.

Indeed, it has been recently shown that new-laid or well-preserved eggs

are free from all micro-organisms. When these appear they have made

their way into the egg through the mechanically injured or otherwise

altered calcareous shell. They do not have their origin in the egg from

the mother. The egg of the bird is perfectly free from micro-organisms

when it is laid. If, however, only traces of pure cultivations of

micro-organisms be in a suitable way applied to such eggs externally

(Lenderer), they always have a fatal effect upon the developing germ,

even when they are not any of the so-called pathogenic microbes.

* * * * *

And now the result of Albini’s breeding experiments upon poultry with

respect to the origin of sex.

From three to six days after intercourse with the cock the hens lay

eggs, from which on the average an equal number of males and females

are developed. In the warmer part of the year the number of males

appears to be greater.

_Better nourishment of parents seems also to exercise an influence over

the sex of the young._

Such eggs as were laid from ten to fifteen days after complete

separation from the cock, gave when hatched generally a distinctly

greater number of females. Albini found that the greater number of

these died of anæmia. He ascribed that to imperfect fertilization, and

considered that development of an excessive number of females was to be

ascribed to the same cause.

Albini inclines towards the theory of Thury, in accordance with which

the principal cause of the development of sex lies in the degree of

ripeness of the ovum. He is opposed to the theory of Coste and Gerbe,

which declares that the ova of the birds and mammals are fertilized

when they fall from the ovary. The place where this took place was,

according to their theory, exactly localized, at the opening of the

Fallopian tube, and not at any place in the length of the tube.

Fertilization in the Fallopian tube or uterus is allowed to be

possible, and it is admitted that, in exceptional cases, fertilization

of the hen’s egg is possible so long as it is not surrounded by the

shell-membrane.

This opinion, however, is in direct contradiction to that of Lenkart

and Newport and many others, who hold that the albumen, which gathers

around the yolk in the oviduct, hinders the penetration of the

spermatozoa into the yolk. When Albini had collected his facts he came

to the conclusion that, in the case of animals which bear many young,

the last are mostly male, and explains this by the hypothesis that the

ova passing through the Fallopian tube thrust the semen back, so that

the ova which come behind are therefore fertilized in a more advanced

stage.

* * * * *

Meyer believes that he has incontestably proved against Ahlfeld that

the sex is determined at conception. He does not appear to be disposed

to admit the existence of male and female ova in the ovary; but he

thinks it absolutely certain that the sex is determined at conception

by the reciprocal action of the ovum and the semen. This view follows

from the fact that, as Thury’s theory demands, a fertilization and a

determination of the sex must necessarily take place as regards time

either at the beginning or the end of the mingling of semen and ovum.

The longer the ovum exists free from the ovary, the longer it remains

without the surrounding of those elements (contained in the ovary)

which are necessary to it. Apparently, in consequence of the absence

of these elements, it is all the time drawing nearer extinction, or

it may at least become gradually less capable of maintaining its own

sex--which is feminine. At least, it appears, before it is overtaken

by the total extinction which threatens it if it is not fertilized,

to lose the energy necessary, when fertilization ensues, to maintain

its sex, and so may become fitted to assume the opposite masculine

sex. This much, however, seems to be quite certain, according to

Mayerhofer, that the human ovary does not contain male and female

ova already possessed of sex. Equally impossible is it to imagine

male and female seminal filaments (spermatozoa) already existing in

the organism, and provided with distinct capacities for generating

definite sexes. We are unacquainted with any special anatomical signs

indicating any such distinction, and do not, even after microscopic

investigation, find ourselves prompted to assume the existence of

such distinct forms as would allow us to conclude the existence of

so fundamental a difference. It is true that in many of the lower

animals different forms of spermatozoa are known. These are developed

in one and the same testicle, and under the microscope whisk about

confusedly with vivacious movements. We find this in the case of a

kind of snail (_Murex brandaris_). If we observe a drop of the semen

of this creature diluted with sea water, the greater number of the

spermatozoa, possessing head, central portion, and tail, move about

very energetically. Amongst them are other spermatozoa, distinctly

larger and of different form, whose shape suggests spindle-like

elements, ending in thin thread-like tails. All these objects exhibit

a striking vivacity of movement. Whether these objects represent a

particular kind of spermatozoa (as some have supposed), exhibiting

definite sexual character, or whether they are not cells, striking on

account of their movements, out of which spermatozoa are developed (the

so-called spermatides or spermatogonia, transition forms out of which

spermatozoa are developed), is at present an open question.

H. A. Pagenstecher attempted an important readjustment of Thury’s

theory, and tried to show that it might be made concordant with what

had been elucidated by previous observations. He holds fast to the

axiom (Joh. Muller, Home, Geoffrey St. Hilaire, etc.), that the embryo

is at first sexless, and that the ovum after its fertilization still

has this character, and must possess the potentiality of developing its

sex in two different directions. The factors which determine sex must

be external to the embryo.

Pagenstecher remarks that the relations which have existed anterior

to the fertilization of the ovum, as well as its age (with which its

ripeness is connected), are from the outset without influence on sex.

The embryonal germ, before its fertilization, is an embryo whose sexual

development is undetermined. In this case fertilization acts as an

external factor in the direction of determining the sexual quality of

this indeterminate embryo.

The act of impregnation would be of influence upon the sex of the

embryo in accordance with the character of the father. That follows

from Pagenstecher’s explanations of Hofacker’s observations. According

to Hofacker we get from men of twenty-four years of age and upwards,

as also from sheep of a certain age, an average of a greater number

of males. In the case of mothers, also, as we have already pointed

out, the sexually-stronger age (Lenkart, Girou de Buzareingues,

Hofacker, Morel de Vindé, Sadler) and the food have an influence upon

the majority of births of female individuals. Here should be added the

experience of Nasse and Van den Bosch. The observations of Dzierzon,

von Siebold, Lenkart, and von Berlepsh, on the development of sex in

bees, and, according to von Siebold, among the Psychids, should also

be taken into consideration. When the females of certain Psychids are

not impregnated they lay only female ova. If they are impregnated,

male ova appear also. The tree-lice (Cestoni, Réaumur) give birth to

living young without impregnation. These are at first only female,

_afterwards males appear as well_. After this impregnation commences,

and the females begin to lay ova.

The experiments of Knight, who found that melons and cucumbers produce

male blossoms under higher temperature and female under lower (which

was verified by Mauz), demonstrate that, in this case, such external

factors as warmth, light, dryness, have an influence upon sex.

Pagenstecher, however, believes that the conditions of origin of sex

are not the same in animals and plants. We must not, he says, from

these observations draw conclusions off-hand respecting the sexual

propagation of plants nor of animals in general.

It must be further pointed out with regard to the thesis that ova which

are emitted last have had more time to ripen, that we must reflect

whether the process of ripening may not have also begun late.

Thury’s observation that the last egg laid by a singing bird developed

a male (communicated by O. Bourrit), and that in the case of hens the

majority of the later eggs were males, seemed to Pagenstecher not quite

certain. He mentions also a method by which, in poultry breeding, the

breeding experiments can be conducted on a regular principle, which I

shall quote word for word:--

“For this experiment a number of hens are taken which may be

anticipated to be “setters,” unless the use of incubators is preferred.

The hens are to be separated, and the eggs which each one lays in her

own particular nest are to be marked with numbers corresponding to the

days on which they were laid.

“The eggs of the different hens are now to be rearranged, so that the

eggs which each particular hen is given to hatch shall, as nearly as

possible, have the same numbers. For example, if the number of the hens

be six, and the period of laying up to the time when the hens begin to

set be thirty days, one hen will have eggs to hatch with the numbers 1

to 5, the next 6 to 10, the third 11 to 15, the fourth 16 to 20, the

fifth 21 to 25, the sixth 26 to 30.

“In this way the doubt will be avoided, which necessarily arises, if I

give the eggs of one hen, although marked, to be hatched by her alone.

“In the latter case, it can very seldom be known with certainty from

which egg-shell a cock or hen issued.

“In this experiment, on the contrary, one can quietly wait until the

cocks and hens in the growing broods of the different hens can be

clearly distinguished and numbered, seeing that each brood has numbers

(of the days of laying) of very nearly the same value. The experiment

is easier and less subject to the possibility of error when the eggs

belong to different varieties and are taken from known parents.”

Fertilization in many cases alters the future sex as soon as it affects

the germ in some corresponding manner. The germ develops itself, and,

in the case of creatures whose ova develop without fertilization,

evolves one, or the other, or both of the sexes. According to

Pagenstecher, fertilization often alters the determination of the sex

of the germs which attain to development in the ova. The point of time

in the life of an ovum, at which it has reached that degree of ripeness

which gives it such a character that the semen can no longer affect the

determination of the sex, cannot be absolutely settled. A more powerful

bull might beget female calves earlier in the late rutting time than an

older one.

After further explanations and critical expositions, which suggest

themselves in the course of the examination of the theory, Pagenstecher

lays stress upon the following important dicta of Thury’s teaching:--

1. Sex depends upon the ripeness of the ovum at the time of

fertilization.

2. The ovum which, at the moment of fertilization, has not yet reached

a certain degree of ripeness, produces a female. If this degree of

ripeness has been passed, the ovum, upon fertilization, produces a male.

3. If at the time of rutting a single ovum is detached from the ovary,

and descends slowly through the genital canal (animals which bear a

single offspring), fertilization taking place at the beginning of the

rutting suffices to produce a female, and at the end of the rutting to

produce a male, provided that the change in the condition of the ovum

takes place normally during its passage through the genital canal.

Both the theory as Thury stated it, and the critical remarks that have

been made upon it, have been further elucidated in many subsequent

works. Here Pictet, Chavannes, C. Vogt, De Philippi, and others, have

taken part. Pictet believes in the uniformity of the sexual life of

vegetables and animals, so that both would be subject to identical

fundamental laws.

The facts which stand in certain relations with the fundamental laws

are numerous, and the manner in which they tend to affect those

fundamental laws occasions various combinations in the variety of

phenomena.

For the animal kingdom Thury adduces a number of observations as the

foundation of his teaching. We shall here turn our attention to some of

them.

We have already pointed out that in the case of the eggs of the singing

birds, which are laid by turns, the young which emerges from the last

strikingly smaller egg, the so-called “nest egg,” is always a male.

According to the theory of Thury, the ripeness of the ovum depends

also upon the place which, in the animals, it occupies in the ovary.

In consequence, according to this author, it is not improbable that

we shall find an irregularity in the successive production of male and

female ova.

If the activity of the generative apparatus of the female should be

increased by any circumstance, in the case of the animals the ripening

of the ovum would be accelerated. The consequence would be an earlier

detachment or emptying out of the ova from the ovary. In consequence,

the generative operations in the animal are of a more complex nature

than in plants, a fact which is of great significance for the

determination of sex.

The continuous intercourse of the male with the female increases

the capacity for accelerating the ripening of the ovum. According

to Burdach the mother animals who do not have frequent intercourse

with the male bear more females, because their ova do not, before

fertilization, attain so high a degree of ripeness as to be able to

develop into males. Also, it appears from observations on animals,

not to be improbable that the male chooses the time of intercourse.

The determination of the chosen time depends upon many influences. The

causes of choice may be sought in many factors. Some of these depend

upon external influences; others have internal causes. The causes may

be general or personal. They may depend upon external form, or be

occasioned by other phenomena of the animal world. It is always easy

for these phenomena, which in their nature are of the most different

kinds, to escape observation.

Amongst cattle and sheep the first-born are more often females.

(Girou.) Also in the human species a greater number of females are

observed amongst the first-born. Here, on the one hand, regular

intercourse with the male is to some extent unfamiliar; whilst, also,

according to Thury, the choice of the date of marriage might be of

importance. The constancy of the births may be explained by the

regularity of the intercourse of the two parents in consequence of the

reciprocal ties which surround family life.

From illegitimate births more girls result than from marriage.

The reason of this might be sought in the influence of the active

excitement of the female at the time at which the conception took

place, that is, shortly after menstruation, when the woman is most

easily excitable.

* * * * *

The various theories respecting the explanation of the production of

sex which are known to us, from the earliest accounts down to the

modern predominance of natural philosophy, have been collected by W.

His. (‘_Archiv für Anthropologie_,’ Band 4, 5.)

Since then, it is true, during the course of successive studies, and

more especially of those which have been made during the present

century, many substantial alterations have appeared in the views held

respecting the cause of the different development of sex. We have seen

this above.

Thus, discoveries have been made which have exercised a very wide

influence, for example, that of the ovum in man and in the other

mammalia (Baer, 1828), or the penetration of the spermatozoa into the

protoplasm of the ovum as a necessary condition of fertilization. In

later times it has been made certain that the head of the spermatozoon

is a nucleus, and that only one spermatozoon penetrates into the

interior of the ovum. Afterwards its head as a nucleus unites with

a nucleus-part of the ovum, forming a new nucleus in the ovule,

which, together with the surrounding protoplasm, serves as the point

of departure of the further processes of development, and in this

condition is described as an oosperm. After this follow other extensive

details of the process of development, which will not be described

here. It may be already seen, from the few principal factors of the

process mentioned, that our theory respecting the development of the

sex in the embryo will have to be substantially altered. We shall here

adduce only the fundamental doctrines respecting the development of

the generative organs laid down by Waldeyer in his masterly work on

the ovary and the ovum. The teaching for which we are indebted to His,

Kölliker, Schäfer-Korschelt, Heider, Duval, Kollmann, Minot, Bonnet,

Bergh, Prénant, Balfour, Romiti, Kuppfer, and others, must also be well

remembered, as well as the acquisitions of new information connected

with the physiology of the embryo, and, of quite recent date, the

mechanism of development (Roux), which can acquaint us more especially

with the particulars respecting the states and processes in the ovule

during the earliest life-stages of its development.

The doctrines of the physiology of metabolism in men and beasts under

different circumstances have exercised so powerful an influence

over our comprehension of the relations of the individual during the

sexual-life, that we practically find in all these teachings a powerful

support, whence we may obtain many elucidations bearing upon the

question lying before us, and may discover the principles necessary to

complete our theory.

But, before entering upon the fundamental principles of the theory

which I have set forth, I wish to mention a treatise of Mayrhofer’s,

the principal results of which I shall briefly recapitulate. After that

I shall mention briefly such information as I have met with respecting

the nutrition of the mother.

Mayrhofer was led by critical notices and the observations of others,

and, further, by his own experiences, to conclusions which he set forth

in propositions, some of which I select here.

In the plants and the lower animals food plays a principal part in the

development of sex. The sex is not generated, but depends upon external

influences over the fruit which is in a state of development. And here

we have a stage which precedes the separate sex in man, in which stage

sexual neutrality must be regarded as normal, where also we find a kind

of hermaphroditism.

Whether sex in the human species is determined at conception, or only

develops itself afterwards, we must attempt to discover from obstetric

experience.

The twins and triplets contained by one chorion are of the same

sex, and have a common placenta in which the blood passages of both

umbilical cords communicate with one another. On this account, also,

many opine that the identity of sex is occasioned by the intermixture

of the blood, an opinion regarded, on the contrary, by others,

with incredulity, because the intermixture of the blood might very

possibly lead merely to a mixture and not to homogeneity, under which

circumstances dissimilarity of development would be possible enough.

We may here adduce the following facts also (Jhering): The armadilloes

produce a number of young in one litter, which are normally developed

in a single chorion, and are of the same sex, as in the case with man

when twins are developed in one chorion.

Heartless monstrosities (_Acardiaci_) are, in spite of imperfect

nutrition (the conditions of proper nutrition by the blood are wanting

in the embryo), of the same sex as normal offspring. Now, cases of this

kind demonstrate that, in the later periods of development, although

the conditions of nutrition are not alike, nevertheless the similarity

of sex in the twins is maintained; so the foundation of the future sex

would be laid at the period of conception. This rule which proves valid

for the twins found in a single chorion, would apply for all human ova

in general, because all possess the capacity of attaining their sexual

character at conception.

According to Mayrhofer, placentæ are rare in which, where there are

two chorions, communication is found between the vessels of the two

umbilical cords. In addition to what has been already mentioned,

Mayrhofer lays down the law, which we find frequently stated in many

quarters, that the older of the two parents has a greater preponderance

in favor of the propagation of his, or her, sex. Especially the

physical maturity on the man’s side enables him to propagate his own

sex, either in connection with younger or older women. A superiority on

the part of the woman produces girls.

Our author only partly supports Thury’s theory, and considers it an

open question whether the time of impregnation has any influence on the

origin of sex. But he lays down this principle, that an economy of the

semen by infrequent indulgence in intercourse is extremely favorable

to the production of males.

It may be possible to obtain more exact data respecting the origin of

sex from the artificial breeding of fish. In this case the properties

of the sperm, as well as of the ova, might be observed at an earlier

date by means of a fertilization effected externally. Attention might

be also paid to the age of the parents. In short, all the factors of

artificial influence upon the development of sex can in this case be

taken in hand and controlled by varying the process of artificial

fertilization. The author does not appear to know that the results

obtained by artificial breeding differ remarkably from those which are

the consequence of the natural multiplication of fish, nor that the

development of sex is unfavorably affected in many ways. The cause of

that lies very likely in the nutrition of the young fry, and perhaps,

also, partly in cross-breeding.

What influence the physical welfare of the parents, and especially

of the mother, has on the sex of the offspring in man, besides other

factors deserving of attention, ought to be discoverable from the

statistics of the lying-in hospitals. This is, in my opinion, hardly to

be expected.

* * * * *

On various occasions, whilst taking into consideration the possibility

of an influence on the part of the parents over the sex of the child

(in such respects as have been placed before us in the literature

dealing with this subject), we often had occasion to direct attention

to the food of the parents. And especially the food of the mother

seemed to us to be of the highest importance.

Now, it is universally known that metabolism is increased during

pregnancy. The products of excretion in the case of pregnant women are

much smaller than the quantity of matter taken in, in the shape of

food. The difference, to a great extent, represents the matter taken

to form the bodily substance of the embryo, in accordance with the

anterior laws which have been fixed by the doctrines of the physiology

of metabolism. It will, then, be necessary to pay particular attention

to the investigation of metabolism. Suggestions are not wanting.

They will be found amongst the observations of leading specialists.

For example, Winckel observed that during pregnancy the temperature

was slightly raised. This increase of temperature must practically

be explained as due to the higher and more productive process of

oxidization, which has to be accomplished by the human female for the

sake of nourishing the fœtus.

During pregnancy the number of blood corpuscles suffers an observable

diminution. Still plainer is the reduction of the quantity of

hæmoglobin, when measured with Fleischl’s hæmatometer. This last

phenomenon is very likely connected with a greater consumption of

hæmoglobin, the substance being used up by oxidization.

Observations of setting hens are not without interest. In their case,

also, a diminution of hæmoglobin is observable during the period of

incubation. The hæmoglobin can sink to nearly 50 per cent. of the

normal amount. With the increase of hæmoglobin in the embryo and its

simultaneous diminution in the mother during incubation, it happens, at

a certain period in the process of development, that the embryo in the

egg and the setting hen possess a nearly equal measure of hæmoglobin

with a nearly equal number of blood corpuscles. An increase of the

quantity of hæmoglobin until the normal amount is reached may be

observed in both towards the end of incubation.

The Rhine salmon each year go up in a well-nourished condition from the

sea into the fresh-water streams to spawn. There they remain several

months. They lose much of their muscular substance. (Miescher.) On the

other hand, a great development of the sexual organs and of sexual

secretions takes place, produced, probably, at the expense of the

used-up muscular substance.

Many have paid particular attention to the nourishment of the maternal

organism. Investigations have also been published dealing with the

nutrition of the parent animals in cases when it was desired to

exercise an influence over the sex.

In fact, we have frequently touched upon such subjects, although only

lightly. Here, as we are about to proceed to the subjects of nutrition

and metabolism in the human female awaiting impregnation, we find

ourselves compelled to acquaint the reader with a number of facts which

permit us to assume a connection between the food supply (including

metabolism) and the development of sex.