1. If the husband is older than the wife more boys are born than girls._The sexual life of woman in its physiological, pathological and hygienic aspects

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

than girls.

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

larger still.

_Hofacker’s_ actual figures were the following:

Father younger than mother 90.1 boys to 100 girls.

Father same age as mother 93.3 boys to 100 girls.

Father 4 to 6 years older than mother 108.8 boys to 100 girls.

Father 6 to 9 years older than mother 124.7 boys to 100 girls.

Father 9 to 12 years older than mother 143.7 boys to 100 girls.

Sadler’s results were closely similar:

Father younger than mother 86 boys to 100 girls.

Father same age as mother 94 boys to 100 girls.

Father 1 to 6 years older than mother 103 boys to 100 girls.

Father 6 to 11 years older than mother 126 boys to 100 girls.

Father 11 to 16 years older than mother 147 boys to 100 girls.

Father 16 years and more older than mother 163 boys to 100 girls.

_Goehlert_ found that the offspring of marriages in which the husband

was younger than the wife were 71 boys and 86 girls; of marriages in

which husband and wife were of the same age, 263 boys and 282 girls; and

of marriages in which the husband was older than the wife, 2,017 boys

and 1,865 girls.

_Wappaeus_, combining the data supplied by these three investigators,

_Hofacker_, _Sadler_ and _Goehlert_, obtained the following sexual

ratios for the entire 8,000 cases (_i. e._, the number of boys born to

each 100 girls born): When the husband was younger than the wife, 88.2;

when husband and wife were of the same age, 93.5; when the husband was

older than the wife, 113.0.

It will be observed that the mean sexual ratio of these 8,000 cases is

109.6; whilst, as we saw above, when a sufficiently large number of

instances is taken, the sexual ratio always closely approximates to

106.3. From this it appears that the numbers dealt with by _Hofacker_,

_Sadler_ and _Goehlert_ in their investigations were too small for the

deduction of trustworthy averages.

The same criticism is applicable to the observations of _Ahlfeld_,

_Breslau_ and _Noirot_, whose results conflict with those just given.

According to _Ahlfeld_, in the case of 1,376 births where the father was

at least 10 years older than the mother, the sexual ratio was only 98.2.

According to _Noirot’s_ data, in cases in which the father was older

than the mother, this ratio was 99.7.

_Oesterlen_ gives the following brief summary of the researches made for

the establishment and confirmation of the law of _Hofacker_ and

_Sadler_:

═══════════════╤══════════╤══════════╤══════════╤══════════╤══════════

│ Father │Father and│ Mother │ Sexual │Number of

AUTHOR. │older than│ mother │older than│ ratio. │instances.

│ mother. │same age. │ father. │ │

───────────────┼──────────┼──────────┼──────────┼──────────┼──────────

Hofacker │ 117.8│ 92.0│ 90.6│ 107.5│ 1,996

Sadler │ 121.4│ 94.8│ 86.5│ 114.7│ 2,008

Goehlert │ 108.2│ 93.3│ 82.6│ 105.3│ 4,584

Noirot │ 99.7│ │ 116.0│ 103.5│ 4,000

Legoyt (Calais)│ 109.9│ 107.9│ 101.6│ 107.9│ 6,006

Legoyt (Paris) │ 104.4│ 102.1│ 97.5│ 102.9│ 52,311

Breslau │ 103.9│ 103.1│ 117.6│ 106.6│ 8,084

═══════════════╧══════════╧══════════╧══════════╧══════════╧══════════

The law of _Hofacker_ and _Sadler_ cannot be regarded as possessing

universal validity, although the figures on which it is based seem to

show pretty clearly that we are justified in regarding the mutual

interaction of the male and female reproductive elements at the moment

of fertilization as effective in the determination of sex. In the

investigations to which we have hitherto alluded it is only the relative

ages of husband and wife that have been taken into account; but other

researches have shown that the absolute age alike of the husband and of

the wife has an influence in the determination of sex.

The influence of the absolute age of the mother in the determination of

sex has been very clearly established. _Ahlfeld_ was the first to draw

attention to the fact that among the children of elderly primiparæ there

was always to be found an excess of boys, and that there was an increase

in this excess proportionate to the greater age of the mother. Among 102

children born to primiparæ over 32 years of age the sexual ratio was

137 : 100; and a later investigation made by the same author in

conjunction with _Schramm_ showed that among 1,038 children born to

primiparæ over 28 years of age the sexual ratio was 124 : 100.

_Hecker_ obtained similar results. Among 432 children born to primiparæ

over thirty years of age the sexual ratio was 133 : 100. _Winckel_,

dealing with primiparæ of the same ages, found a sexual ratio of

136.8 : 100.

_Düsing_, examining the records of the lying-in hospitals of Leipzig,

Dresden and Jena and thus obtaining a very large number of instances

whereon to base his conclusions, confirmed the view that elderly

primiparæ give birth to an excess of boys, and further that the older

they are the larger the excess of male births. He drew up the following

table:

══════════╤════════════╤════════════╤════════════╤════════════╤═══════════

Age of │ Leipzig. │ Dresden. │ Jena. │ Total Nos. │ Sexual

primiparæ.│Boys. Girls.│Boys. Girls.│Boys. Girls.│Boys. Girls.│ ratio.

──────────┼────────────┼────────────┼────────────┼────────────┼───────────

15 │ 1 : −│ 1 : 2│ 1 : −│ 3 : 2│} 549 : 494

│ │ │ │ │ = 111.1

16 │ 4 : 4│ 6 : 10│ 2 : 2│ 12 : 16│ „

17 │ 23 : 13│ 20 : 15│ 9 : 7│ 52 : 35│ „

18 │ 67 : 55│ 103 : 100│ 17 : 13│ 187 : 168│ „

19 │ 110 : 103│ 152 : 141│ 33 : 29│ 295 : 273│ „

20 │ 148 : 147│ 187 : 185│ 32 : 45│ 367 : 377│} 807 : 781

│ │ │ │ │ = 103.3

21 │ 157 : 145│ 241 : 201│ 42 : 57│ 440 : 404│ „

22 │ 120 : 133│ 191 : 207│ 48 : 53│ 359 : 393│} 903 : 962

│ │ │ │ │ = 93.9

23 │ 106 : 108│ 168 : 149│ 51 : 51│ 325 : 308│ „

24 │ 71 : 105│ 111 : 118│ 37 : 38│ 219 : 261│ „

25 │ 79 : 57│ 73 : 72│ 35 : 27│ 187 : 156│} 531 : 469

│ │ │ │ │ = 113.2

26 │ 45 : 35│ 30 : 43│ 20 : 20│ 125 : 98│ „

27 │ 31 : 35│ 52 : 55│ 10 : 12│ 93 : 102│ „

28 │ 32 : 33│ 26 : 33│ 19 : 16│ 77 : 72│ „

29 │ 19 : 10│ 26 : 18│ 4 : 13│ 49 : 41│ „

30 │ 9 : 15│ 30 : 13│ 9 : 6│ 48 : 34│} 155 : 104

│ │ │ │ │ = 150.0

31 │ 3 : 8│ 15 : 11│ 3 : 3│ 21 : 22│ „

32 │ 5 : 6│ 12 : 9│ 7 : 3│ 24 : 18│ „

33 │ 2 : 2│ 5 : 5│ 5 : 2│ 12 : 9│ „

34 │ 4 : −│ 8 : 5│ 2 : −│ 14 : 5│ „

35 │ 2 : −│ 9 : 3│ 2 : 1│ 13 : 4│ „

36 │ 1 : −│ 3 : 3│ 1 : 1│ 5 : 4│ „

37 │ 4 : 1│ 4 : 3│ 1 : −│ 9 : 4│ „

38 │ − : −│ − : 1│ 1 : −│ 1 : 1│ „

39 │ − : −│ 4 : −│ 1 : −│ 5 : −│ „

40 │ 1 : 1│ 2 : 1│ 1 : −│ 4 : 2│ „

41 │ − : −│ − : 1│ − : −│ − : 1│ „

──────────┴────────────┴────────────┴────────────┴────────────┴───────────

As an explanation of this statistically proved fact, that elderly

primiparæ gave birth to a large excess of boys, _Düsing_ suggests that

these women who conceive for the first time comparatively late in life,

are, prior to the conception, in a state corresponding with that of a

lower animal species suffering from a deficiency of males, and for this

reason exhibit a tendency to procreate a larger number of individuals of

the deficient sex. In multiparæ also it is possible to trace the

influence of a deficiency of male individuals. When there is such a

deficiency the interval between successive births is unduly protracted.

_Düsing_ found (once more from the records of the lying-in hospitals of

Dresden, Leipzig and Jena) that the longer the interval between one

parturition and the next the longer, that is to say, the mother has had

to wait for her next conception, the greater is the excess of male

births. _Düsing_ therefore lays down the law: “Delayed impregnation

gives rise to an excess of male births.”

═══════════╤════════════╤════════════╤════════════╤════════════╤═══════

Age of │ Leipzig. │ Dresden. │ Jena. │ Total Nos. │Sexual

primiparæ. │Boys. Girls.│Boys. Girls.│Boys. Girls.│Boys. Girls.│ratio.

───────────┼────────────┼────────────┼────────────┼────────────┼───────

1 │ 162 : 158 │ 194 : 178 │ 58 : 45 │ 414 : 381 │ 108.6

2 │ 366 : 307 │ 374 : 361 │ 168 : 145 │ 908 : 813 │ 111.6

3 │ 198 : 196 │ 207 : 194 │ 116 : 94 │ 521 : 484 │ 107.7

4 │ 127 : 109 │ 132 : 106 │ 59 : 45 │ 318 : 260 │} 115.7

5 │ 59 : 54 │ 55 : 54 │ 38 : 38 │ 152 : 146 │ „

6 │ 61 : 62 │ 52 : 49 │ 49 : 24 │ 162 : 135 │} 121.9

8, 9 and 10│ 18 : 16 │ 41 : 23 │ 16 : 24 │ 75 : 63 │ „

11 and more│ 5 : 15 │ 12 : 9 │ 4 : 6 │ 41 : 30 │ „

───────────┴────────────┴────────────┴────────────┴────────────┴───────

Totals: 4,903 births, 2,591 m.; 2,312 f.; sexual ratio = 112.06.

_Bidder_ considers that his own observations entitle him to modify

_Ahlfeld’s_ dictum regarding the influence of age in primiparæ in giving

rise to an excess of male births. He tabulates his results as follows:

═════════════════╤═════════════════╤═════════════════

AGE OF MOTHER. │Number of cases. │ Sexual ratio.

─────────────────┼─────────────────┼─────────────────

17 to 20 │ 80│ 122.2

20 to 22 │ 405│ 130.1

22 to 24 │ 369│ 109.9

24 to 26 │ 1,138│ 104.6

26 to 30 │ 2,049│ 105.5

30 to 32 │ 878│ 112.5

32 to 36 │ 1,120│ 119.6

36 to 39 │ 676│ 123.1

40 and upward │ 215│ 131.5

═════════════════╧═════════════════╧═════════════════

and formulates the following thesis: Very young primiparæ give birth to

an excess of boys; primiparæ in the first bloom of womanhood give birth

to an excess of girls; later, however, as the age of the primiparæ

increases the excess of male births soon reappears and rapidly

increases.

_Hofacker’s_ data and the researches of _Hampe_ agree with those of

_Bidder_ in showing that to very young primiparæ, as well as to elderly

primiparæ, an excess of boys is born. Among the offspring of 363

mothers, at ages varying from 16 to 26 years, _Hofacker_ found the

sexual ratio to be 121; among the offspring of 1,056 mothers, at ages 26

to 36, the ratio was 101; and among the offspring of 567 mothers at ages

36 to 46, the ratio was 111. _Hampe_ tabulated 5,992 instances as

follows:

═══════════════════════╤═══════════════════════╤═══════════════════════

AGE OF MOTHER. │ Number of instances. │ Sexual ratio.

───────────────────────┼───────────────────────┼───────────────────────

Below 20 years │ 56│ 107.7

20 to 25 years │ 871│ 90.6

25 to 30 years │ 1,633│ 114.9

30 to 35 years │ 1,631│ 108.3

35 to 40 years │ 1,185│ 117.1

Over 40 years │ 616│ 124.0

═══════════════════════╧═══════════════════════╧═══════════════════════

We learn, therefore, that if the age of the progenitors is to be

regarded as one of the causes by which sex is determined, we must take

into consideration not only the relative ages of husband and wife but,

in addition, the absolute age of the wife.

_Goehlert_ undertook a statistical investigation in which the absolute

age of the husband was taken into consideration as well as that of the

wife. From this it appeared that the maximum sexual ratio was exhibited

when the father was between the ages of 30 and 35 years. When the age of

the mother is treated as the determining influence, we find the maximum

sexual ratio in the offspring of mothers between the ages of 25 and 30

years. _Goehlert_ believes, however, that the paternal influence is more

powerful than the maternal in the determination of sex. The respective

influences are compared in the following table:

══════════════╤═══════════════════════════════════════════════════════

AGE OF FATHER.│ AGE OF MOTHER.

──────────────┼─────────────┬─────────────┬─────────────┬─────────────

„ │ 20 to 30 │ 30 to 40 │ Over 40 │ Totals.

│ years. │ years. │ years. │

──────────────┼─────────────┼─────────────┼─────────────┼─────────────

25 to 35 years│ 105.76│ 107.87│ 109.14│ 106.6

35 to 45 years│ 102.8│ 105.1│ 105.3│ 104.7

Over 45 years │ │ 104.3│ 103.9│ 109.1

In general │ 105.25│ 105.97│ 104.9│ 105.5

══════════════╧═════════════╧═════════════╧═════════════╧═════════════

_Geissler_, studying the data obtainable regarding the sexual ratio

during a 10–year period in the Kingdom of Saxony, ascertained that in

families possessing two children or more there was a very definite

distribution of the possible sex-combinations. Where there was an even

number of children those families were in the majority in which the

number of boys and girls was identical. If the number of children in the

family is an unequal one, those combinations are most frequent in which

the number of boys exceeds the number of girls by one; next in frequency

are those combinations reversed to this, _i. e._, in which the number of

girls exceeds the number of boys by one. All other combinations are

comparatively infrequent in proportion as the discrepancy in number

between boys and girls is larger. Rarest of all are families in which

the children are all of the same sex; and among these, again, the most

unusual are those consisting of boys only.

This distribution of the sex-combination is believed by _Geissler_ to

depend upon the fact that in the first birth and all the subsequent

births there is generally speaking a slight advantage in favour of the

male sex. It has not been proved that the sex of the first-born

exercises a determining influence on the sex of the subsequent children.

It does, however, seem clear that in the case of parents who have given

birth in succession to several children of one sex only, there exists

some definite obstacle to the procreation of children of the opposite

sex. Putting these exceptions out of consideration, there seems to exist

a tendency in the later births of a series toward the procreation, more

especially of that sex which has been absent or deficient in the earlier

births of the series. The strength of this equalizing tendency increases

as soon as it has for the first time manifest itself. It is always

greater when the sex deficient in the earlier births of the series has

been the male.

I have myself undertaken a statistical investigation of the births

occurring in the reigning families of Europe and in the families of the

leading members of the aristocracy. The necessary particulars are to be

obtained from the genealogical court calendars; and it is my belief that

the data obtained regarding these uppermost strata of society are

comparatively free from many sources of error by which the ordinary

statistics of the subject are apt to be invalidated. For 556 marriages

there were 1,972 births, comprising 1,023 boys and 949 girls, and thus

exhibiting a sexual ratio of 107.7.

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

drawn up:

══════════════════════════════════════════════════╤══════╤══════╤══════

│ │ │Sexual

│Boys. │Girls.│ratio.

──────────────────────────────────────────────────┼──────┼──────┼──────

Husband older than wife by one to five years │ 294│ 283│ 103.8

Husband older than wife by more than five and less│ │ │

than ten years │ 327│ 306│ 106.8

Husband older than wife by more than ten and less │ │ │

than fifteen years │ 190│ 167│ 113.7

Husband older than wife by more than fifteen years│ 138│ 113│ 122.1

Husband same age as wife │ 34│ 42│ 80.9

Husband younger than wife │ 40│ 38│ 105.2

══════════════════════════════════════════════════╧══════╧══════╧══════

From these figures we may deduce the following conclusions, which are

not wholly concordant with the law of _Hofacker_ and _Sadler_: When the

husband is older than the wife the excess of male births among the

offspring is greater than it is in the case of an average drawn from the

offspring of all marriages (in my cases the difference was 111.8 as

compared with 107.7). But a closer analysis shows the difference to be

less simple than at first sight appears. If the husband is older than

the wife by one to five years, the excess of male births among their

offspring (103.8) is less than in the average of all marriages (107.7);

the same is true of the offspring of marriages in which the husband is

more than five and less than ten years older than the wife, though the

difference here is very trifling (106.8 as compared with 107.7). It is

not till we come to the offspring of marriages in which the husband is

from ten to fifteen years older than the wife that the increase in the

excess of male births becomes notable (113.7 as compared with 107.7);

and when the husband is more than fifteen years older than the wife the

excess of males is higher still (122.1).

If we arrange these data so as to show, in cases in which the husband is

older than the wife, the additional influence of the absolute age of the

wife, we obtain results which partially conflict with those of _Bidder_,

as follows:

HUSBAND OLDER THAN WIFE. │ │ │Sexual

│Boys. │Girls.│ratio.

Wife’s age, 15 to 20 years │ 280│ 287│ 97.6

Wife’s age, 20 to 26 years │ 595│ 513│ 116.0

Wife’s age, 26 to 33 years │ 74│ 69│ 110.1

Thus we see that when the wife is very young, i e., less than twenty

years of age, even though the husband is older than the wife, there is

among their offspring no excess of male births, but the contrary—a

sexual ratio of 97.6 only. Most marked is the excess of boys in cases in

which the husband is older than the wife, and the age of the wife is

from twenty to twenty-five years. When the husband is older than the

wife, and the wife’s age lies between twenty-five and thirty-two years,

the excess of male births is not so great, though still considerable.

Hence it appears that the law of _Hofacker_ and _Sadler_, which cannot

be regarded as fully valid in the terms in which it was originally

expressed, must be modified as follows: If the husband is at least 10

years older than the wife, and the latter is at an age when her

reproductive capacity is at its maximum (twenty to twenty-five years),

the offspring exhibit a notable excess of male births. There is still a

considerable excess of male births in the offspring of marriages in

which the husband is at least ten years older than the wife, and the

wife is more than twenty-five years of age. On the other hand fewer boys

are born than girls as the offspring of marriages in which, although the

husband is older than the wife, the wife has not yet attained the age of

maximum reproductive capacity—_i. e._, is less than twenty years of age.

The excess of female births is most marked when the husband and wife are

of the same age. When the wife is older than the husband there is a

moderate excess of male births.

I admit, however, that the figures upon which I have based these

conclusions are, like those of _Hofacker_, too few in number for the

foundation of trustworthy inferences. The instances in my computation

number 1,972; those in that of _Hofacker_, 1,996; but, as I have already

remarked, there are reasons for believing that the data I have employed

admit of the introduction of fewer sources of error.

The influence of the absolute age of the mother in the determination of

sex having been statistically proved, many have inferred that this

determination is not effected during the instant of fertilization, but

occurs at a later stage of intra-uterine life, and is influenced by the

manner in which the embryo is nourished by the maternal organism. It is

suggested that elderly and immature mothers are unable to furnish the

embryo with nutriment so well as those mothers who are at the age of

maximum reproductive capacity, and that upon this fact depends the

excess of male births in the latter case. (We shall return to this

matter—the influence of deficient nutrition in relation to the excess of

male births). But the proof of the fact that the absolute age of the

father has also an influence in the determination of the sex of the

offspring offers a ground for opposing this assumption that the sex of

the embryo is determined during intra-uterine life subsequent to

fertilization, and suggests that the father also exercises a determining

influence in the origination of sex during the act of fertilization.

The absolute age of the husband seems also to have some influence upon

the sexual ratio. The absolute age, like the relative age, of the father

appears favourable to the procreation of a greater excess of boys. Thus,

_Hofacker_ found in 1,193 cases, in which the age of the father was from

twenty-four to thirty-six years, that the sexual ratio was 100; in 683

cases in which the age of the father was from thirty-six to forty-eight

years, the sexual ratio was 114; and in 105 cases, in which the age of

the father was from forty-eight to sixty years, the sexual ratio was

169.

In investigations based upon larger collections of cases _Schumann_ and

_Düsing_ have endeavoured to determine the variation in the sexual ratio

according to the absolute age of the father.

_Düsing_ examined the statistics of births in Norway, Alsace-Lorraine

and Berlin, and from the data thus obtained he compiled the following

table:

════════╤════════════════════╤════════════════════╤════════════════════

AGE OF │ 30 TO 35 YEARS. │ 25 TO 30 YEARS. │ 20 TO 25 YEARS.

MOTHER. │ │ │

────────┼──────┬──────┬──────┼──────┬──────┬──────┼──────┬──────┬──────

AGE OF │Boys. │Girls.│Sexual│Boys. │Girls.│Sexual│Boys. │Girls.│Sexual

FATHER. │ │ │ratio.│ │ │ratio.│ │ │ratio.

────────┼──────┼──────┼──────┼──────┼──────┼──────┼──────┼──────┼──────

15 to 30│ 8,525│ 7,887│ 108.1│27,389│25,843│ 106.0│21,560│20,330│ 106.0

years │ │ │ │ │ │ │ │ │

30 to 35│23,283│21,823│ 106.9│23,394│23,486│ 103.9│ 7,954│ 7,469│ 106.5

years │ │ │ │ │ │ │ │ │

35 to 40│17,885│17,070│ 104.7│10,272│ 9,838│ 104.2│ 2,426│ 2,416│ 100.4

years │ │ │ │ │ │ │ │ │

40 to 45│ 7,972│ 7,681│ 103.8│ 3,165│ 3,058│ 103.5│ }│ 1,100│ 105.0

years │ │ │ │ │ │ │ 1,154│ │

Over 45 │ 4,220│ 3,997│ 105.6│ 1,734│ 1,525│ 113.8│ „ │ „ │ „

years │ │ │ │ │ │ │ │ │

────────┴──────┴──────┴──────┴──────┴──────┴──────┴──────┴──────┴──────

In this table we find the births arranged in relation to varying ages of

the fathers and in relation to mothers whose ages are tabulated in three

classes, the ages of the latter being those at which they are most

prolific. The table shows clearly that the excess of boys is larger at

the beginning and at the end of each column. Thus, the age of the mother

remaining constant, young fathers and elderly fathers procreate a larger

proportion of boys than do fathers of intermediate age.

But I find in this table, which is based upon a very large number of

instances indeed, a confirmation of the thesis which I stated above, for

the highest sexual ratio of 113.8 is in this table found in the case of

fathers over forty-five years of age who are married to mothers of ages

twenty-five to thirty years; this is, as I said, the case in which “the

husband is at least ten years older than the wife, and the latter is at

the age at which her reproductive capacity is at its maximum.”

From such figures as these, which seem to show the influence of the

absolute age of the father upon the determination of sex, it has by many

been inferred that the man exercises a preponderating influence upon the

determination of the sex of the embryo, impressing his own sex upon it,

and that the greater the sexual potency of the begetter the more

powerful also is the influence exercised by the latter; that the point

of first importance in this connection is the sexual capacity of the

man; and that the excess of male births increases _pari passu_ with the

increase in the potency of the procreating male.

Two additional considerations have been adduced to demonstrate the

influence of the father in determining the sex of the offspring. The

first of these is a comparison of the ratio between male and female

births in towns and in rural districts, respectively; and the second is

a comparison between the ratio of males to females in the offspring of

married and of unmarried parents, respectively.

In towns the excess of male births is smaller than it is in the country.

The average sexual ratio in Prussia during the five-year period, 1875 to

1880, is given by _Düsing_ as follows:

In Berlin 105.70

In other large towns 105.72

In medium sized towns 105.44

In small towns 106.17

In rural districts 106.62

The indisputable fact that in towns more girls are born than in rural

districts is referred to the fact that in the country the husband

usually enters on marriage with his virile powers completely unimpaired,

whereas in towns many men only marry after they have for many years

expended their best forces in irregular sexual intercourse, and thus

reserve for their wives only the dregs. But, as we shall show presently,

the difference between town and country in this respect is susceptible

of a different interpretation.

It has also been asserted (_Horn_) that extra-conjugal sexual

intercourse is favourable to the procreation of boys, the suggestion

being that the greater sexual vigour in the former case determines a

preponderance of males in the offspring; but this assumption is

invalidated by the statistical evidence which now accumulates, that

among illegitimate offspring there is a smaller excess of boys than

among legitimate offspring. _Babbage_, for instance, came to this

conclusion as a result of the comparison of 1,000,000 illegitimate

births with 14,000,000 legitimate births. On the other hand, the

following utterance of _Ploss_ appears extremely artificial: “In a

country in which illegitimate births are very numerous, in which the

illegitimate children are for the most part begotten by enervated

debauchees, the excess of male births is smaller; but in a country in

which the illegitimate births are less numerous, and in which the

illegitimate infants are for the most part the fruit of love and are

begotten by youthful lovers, the excess of male offspring is larger.”

Next to the age of the progenitors, their nutritive condition is shown

by statistical investigations to exercise an important influence in the

determination of sex. The following proposition has, in fact, been

established: Where the supply of nutriment is deficient, the offspring

contains an excessive proportion of boys.

_Ploss_, in an article on “The Causes of Variations in the Sexual

Ratio,” published in twelfth volume of the “Berliner geburtsh.

Monatsheft,” has collected a number of statistical data to demonstrate

that the determination of sex is principally dependent upon the

nutritive condition of the mother. In his opinion the determination of

the sex of the embryo depends neither upon the quality of the ovum nor

upon that of the spermatozoon, nor again upon the reciprocal influences

exerted by ovum and spermatozoon on one another. During the earliest

time after fertilization the embryo is sexually neutral and only later,

as a result of some new influence acting upon it, does it receive an

impulse toward the formation either of the male or of the female sex.

Among all the external conditions which are capable during this period

of exercising a determinative influence the most important are the

nutritive conditions, for nutrition is the most important factor in

determining the form of the young animal, and most of the other outward

conditions, such as light, heat, and chemical changes, affect the embryo

in a mediate manner only, through the changes they are respectively

capable of inducing in its nutrition and metabolism. But _Ploss_ is not

content with asserting that the nutritive condition of the mother is of

great importance in determining the sex of the embryo; he goes further

than this, and declares that it is scanty nutrition of the mother which

especially gives rise to the birth of males, whereas abundant nutrition

of the mother tends to give rise to the birth of females. He refers to

observations made in respect of other animals than man. _St. Hilaire_

observed that among the underfed animals in menageries there was an

excess of male births. _Hofacker_ and _Girou de Bazarcingues_ have noted

similar phenomena in the case of domestic animals; they found that when

these were richly fed they gave birth to an excess of females, but that

when they were poorly nourished they gave birth, on the contrary, to an

excess of males. Among sheep, with whom the number of male and of female

births is approximately identical, _Martegoute_ found that those animals

which had given birth to female lambs had on the average a greater

weight than those ewes which had given birth to male lambs. During the

period of lactation, also, the former lost weight more than the latter.

When _Ploss_ had further ascertained that among those engaged in the

fur-trade it is the established belief that from fruitful regions the

skins chiefly of female animals will be obtained, but from barren

regions, on the other hand, among the skins obtained those of male

animals will preponderate, it appeared to him that he was justified in

drawing the conclusion that among the mammalia a well-nourished mother,

one capable of providing abundant nutriment for her offspring, is, on

the whole, more likely to give birth to a female than to a male, and

conversely. He then endeavoured, by reference to the statistics of

population, to show that in the case of human beings also, when the

mother is exceptionally well nourished, there is especial likelihood of

a girl being born; whereas when the mother is ill nourished she is more

likely to give birth to a boy—odd as it may seem, at first sight, that a

rich diet should determine the production of the so-called less powerful

sex, the female; and conversely. (_Ploss_, be it noted however, denies

that male new-born infants are more powerful than female.) The fact that

in the country, comparatively speaking, many more boys are born than in

towns (_vide supra_) is explained by _Ploss_ as dependent on the fact

that townswomen are on the whole better nourished than the countrywomen,

owing to the greater consumption of meat by the former.

The circumstance again (likewise alluded to above), that in the case of

illegitimate births almost always the excess of male births is less

marked than in the case of the offspring of legal unions, is regarded by

_Ploss_ as offering further proof of the influence of nutritive

conditions upon the determination of sex. Illegitimate mothers are on

the average women at the very best age for child-bearing, women who have

worked vigorously, are themselves well nourished, and are therefore

better able to nourish their unborn offspring than (on the average)

married women. Further, it is a remarkable fact that in Saxony, regions

of which the elevation above the sea-level is less than 1,000 feet,

produce comparatively more girls than regions at an altitude of 1,000 to

2,000 feet above the sea. This _Ploss_ refers to the worse nutrition of

the women living at the higher altitude, for the fact is well known that

the higher we go above the sea the less fertile is the soil and the more

limited is its produce.

Starting from the view that the lower classes of the population are in

good years better nourished than they are in bad years, _Ploss_ compared

statistically the rise and fall of the prices of foodstuffs, in Saxony,

with the variations of the sexual ratio in the same kingdom; and he

found, in correspondence with his theory, that in bad times there was a

greater excess of male births than there was during periods in which

food was cheaper. Moreover, the consumption of meat appeared to have

more influence upon the variations in the sexual ratio than was

exercised by the consumption of vegetable foodstuffs. _Ploss_

endeavoured to show graphically that with an increase in the price of

provisions there corresponded an increase in the excess of male births,

and _vice versa_.

That after times of great wars, pestilence, and emigration, in which the

male portion of the population has been decimated, there occurs a

notable increase in the excess of male births, is explained by _Ploss_

by the assumption that in consequence of the deficiency of male labour,

the general supply of provisions is deficient, just as it is after years

of bad harvests; hence, in consequence of the scanty nutrition of the

mothers, the number of female births is depressed and the number of male

births increases. Those countries which in general possess a more

thriving population, such as Saxony, England, Belgium, Prussia, etc.,

exhibit a smaller excess of male births when compared with those

countries in which a more widespread poverty exists, such as Russia,

Lombardy, Bohemia, and even France. With increasing prosperity,

fruitfulness increases, and there is an increase also in the proportion

of female births.

These views of _Ploss’s_ are, however, rightly contested by _Breslau_

and _Wappaeus_.

_Breslau_ (“The Causes of the Determination of Sex”) offers in the first

place theoretical objections to the view that nutritive conditions in

the mother are determinative in the production of the sex of the

offspring; and he then proceeds to quote statistical data which are

opposed to any such theory. He rightly insists, in the first place,

that, inasmuch as it is unquestionable that in the act of fertilization

the spermatozoon induces in the ovum certain changes, the effect of

which is manifested in days far later than those of intra-uterine life,

by the production of the most manifold and various somatic and psychical

resemblances to the father, it is obvious that this single occurrence of

the fusion of the spermatozoon, the bearer of the paternal influences,

with the ovum is competent to induce in the ovum a molecular arrangement

upon which the determination of sex may be supposed to depend—it is not

necessary to suppose that for this determination, repeated actions, or a

prolonged period of time, is requisite.

In this connection a reference to birds is instructive, for in this

division of the animal kingdom we seem absolutely compelled to assume

that the sex of the offspring is irrevocably determined in the moment of

fertilization. “In birds, who lay an egg every day, eggs which are kept

all at the same temperature during the period of incubation, and some of

which develop into cock and others into hen birds—how is it possible to

imagine that the nutritive condition of the parent is determinative of

the sex of the offspring, since this nutritive condition cannot

reasonably be supposed to change to any notable extent from one day to

the next and then back again?”

The paternal influence in the determination of sex is regarded by

_Breslau_ as likely to be at least as important as that exercised by the

mother. Unquestionably the semen is subject to certain variations in

quality and in quantity, and it is possible that these variations may

make themselves felt in the subsequent development of the embryo. Of the

semen, as of all secretions, we can assume with some probability that in

certain conditions (conditions which are, indeed, but little

understood), it may exhibit a greater or less intensity in its

stimulating qualities, and that in this way it may be subject to

changes, according to which it will tend to influence the development of

the embryo, now in the female, and now in the male direction. Again, in

view of the continued interchange of nutritive materials between the

embryo and the maternal organism, it is probable enough that the

constitution of the maternal organism and likewise that of the ovum, at

the moment of fertilization, are not matters of indifference to the

determination of sex. But to attribute to the nutritive condition of the

maternal organism the sole or even the principal influence in the

determination of the sex is an unjustifiable assumption.

The proofs alleged by _Ploss_ from the animal world in support of his

thesis, viz., that in the case of poorly nourished animals there is a

marked excess of male offspring, are justly controverted by _Breslau_

with the remark that the observations on animals are but few in number,

and further that we know nothing whatever regarding the normal sexual

ratios among the offspring of such animals as lions, tigers, hyænas,

bears, etc., in the free state.

If, again, domestic animals when well nourished give birth to an excess

of female offspring, and when ill nourished and overworked to an excess

of male offspring, in the former case we can only regard the excess of

female births as a pathological phenomenon, inasmuch as a superabundant

supply of nutriment is not that which furnishes the highest powers or is

most suited to the preservation of life. Again, the accounts given by

fur-dealers are quite untrustworthy, since these men commonly obtain

their goods at third and fourth hand; moreover, most of the animals

whose pelts form articles of commerce, are beasts of prey, such as the

otter, the lynx, the bear, the wolf, the fox, etc.—and these animals

have no “pasturage.” Among vegetable-feeding animals the females are no

doubt found on the pasturage more often than the males, for the reason

that the females have to nourish both themselves and their young,

whereas the males, which have themselves only to provide for, are

contented with less food and inhabit chiefly more retired and less

fertile regions; they are also shyer and are less easily shot and

trapped. Regarding statistical data relating to the influence of

nutrition on the production of boys, _Breslau_ shows, from the figures

of the Canton of Zurich, that with few exceptions, the years in which

the price of corn was lowest were the years in which the production of

boys was greatest, and _vice versa_—the exact opposite of the results

obtained by _Ploss_ from his examination of the figures relating to

births and the price of provisions in Saxony.

_Wappaeus_ contests the conclusions of _Ploss_ even more vigorously, and

adduces the statistics of Sweden in the 20–year period 1770 to 1790, in

which period this kingdom repeatedly suffered from famine in consequence

of failure of the crops, so that the births and deaths were largely

affected. It appeared, however, that the more abundant or more scanty

nutrition of the inhabitants of Sweden during this period had no marked

influence upon the sexual ratio.

If scanty nutrition of the mother had, in fact, any influence upon the

determination of the sex of the embryo in the direction alleged by

_Ploss_, viz., so as to bring about the birth of a greater excess of

boys, this influence should be manifested with exceptional clearness in

the case of twins, for it is obvious that the nutriment that is

insufficient for one embryo would be still scantier for two. Hence

various statistical investigations have been undertaken to determine the

sexual ratio in the case of twin births. _Ploss_ found that in Saxony,

in the case of 23,420 twin births, the sexual ratio was 106.7 boys to

100 girls; _Moser_ gives the sexual ratio in the case of twin births as

106; _Meckel von Hemsbach_ gives it as 105.4; _Hecker_, 116 and 122;

_Sickel_, 112.3. _Düsing_ combined the figures relating to twin births

in various lying-in hospitals, published by _Hecker_, _Sickel_,

_Baillarger_, _Siebold_, _Elsässer_, and _Levy_, respectively, and thus

obtained a sexual ratio of 121.5 boys to 100 girls. This excess of boys

is notably greater than among births in general.

But other statistical data are available which show a reversed

condition, viz., that in the case of twin births the sexual ratio is

lower than usual. According to _von Frick’s_ collection of twin births

in Prussia, the sexual ratio was 104.7 boys to 100 girls; whereas in the

case of single births in the same country the sexual ratio was 106.35 to

100. _Riecke_, in Württemberg, in the case of 60 twin births found 58

boys and 62 girls. In the case of twin births observed by _Braun_,

_Chiari_, and _Späth_, 94 in all, the children were in 64 of these of

identical sexes, namely, in 30 instances boys, and in 34 instances

girls. According to _Breslau_, in the case of twin births in the Canton

Zurich, the sexual ratio was 104.1 to 100; whereas in the case of single

births the sexual ratio was 106.2 to 100.

As regards triplets the reports of the sexual ratio vary from

111.76 : 100 (_Meckel von Hemsbach_) to 104.55 : 100 (_Neefe_).

It is obvious that the statistical data at present available regarding

the sexual ratio in the case of multiple births are far too variable for

it to be possible to base upon them any valid conclusions as to the

influence of the nutritive condition of the mother upon the

determination of the sex of the offspring. And taken as a whole the

statistical data hitherto available do not enable us to infer with

confidence that nutritive conditions, and more especially the nutritive

state of the maternal organism, exercise any effect upon the

determination of the sex of the offspring.

Another attempt at the utilization of statistics has been to ascertain

whether the time of fertilization in relation to menstruation, (in the

first days after the flow, or later in the intermenstrual interval) has

any influence upon the determination of sex. The starting point in this

investigation was the earlier view that sex depends upon the state of

the ovum, and the belief that a very favourable state of ovum and sperm

favours the production of the female sex. The ovum, after its discharge

from the ovary, like the spermatozoon after its discharge from the

testicle, tends sooner or later toward death, and the only thing that

can save either from this ultimate fate, is for the two to unite to form

a new organism. Precisely what moment in the history of the detached

ovum is the most favourable, is a matter regarding which we have no

exact information, but it is probable that at the moment of its

discharge from the ruptured follicle, it is at the zenith of its vital

powers. On this theory the determination of sex depends upon the period

at which, after its liberation from the follicle, the ovum encounters a

spermatozoon; the ovum which is fertilized early in its career becomes a

female embryo; the ovum, on the other hand, which is not fertilized

until it has become comparatively old, becomes a male embryo. But, as

_Hensen_ points out, a spermatozoon, according to _its_ condition, may

either fail sufficiently to fortify an ovum which itself is in good

condition; or, on the other hand, a powerful spermatozoon may fortify an

ovum of deficient vitality. But it is difficult to say precisely on what

considerations the greater or less vitality of the spermatozoon

depends—or, to speak more in accordance with the terms of the theory, we

do not know exactly what makes it a good spermatozoon or the reverse. It

may be “bad,” either because it has remained too long in the testicle or

because it has been discharged too quickly, is too recently secreted;

moreover, a long sojourn of the spermatozoon in the uterus will

doubtless suffice to lower its vitality.

The Jews, more especially, whose religious ordinances forbid them to

have sexual intercourse either during or shortly after menstruation, and

among whom there is a great excess of male births, have been adduced as

a proof of the thesis that sexual intercourse during the later part of

the intermenstrual interval tends to favour the procreation of boys. In

Leviticus xv. 19, we read: “And if a woman have an issue, and her issue

in her flesh be blood, she shall be put apart seven days.” From the

commentary in the Talmud it appears that these seven days are to be

reckoned from the commencement of the flow. Statistical reports from

various countries show that among the Jews there is a greater excess of

male births than among the other inhabitants of the respective

countries. The overplus of male births exhibited by the Jews varies from

1 to 15%, the difference probably depending on the fact that the number

of instances under consideration is too small for uniform results to be

possible. In Prussia, during the period 1820 to 1834, the sexual ratio

among the Jewish births was 111 : 100; during the period 1849 to 1852 it

was 106 : 100; in Hungary during the period 1835 to 1855 it was

117.1 : 100; in Sweden, 1851 to 1855, it was 108 : 100. Among

illegitimate children of the Jewish community the sexual ratio was, in

Austria, 123.9, in Prussia, 118.6.

_Fürst_, examining the cases in _von Braun’s_ clinic, and making a

statistical collection of the days of conception and of delivery, has

endeavoured to prove that “there is an excess of boys when conception

occurs during the period of post-menstrual anæmia.” His figures show, in

fact, a very notable excess of boys in cases in which conception has

occurred during the five days immediately following the cessation the

menstrual flow; and an excess of girls when conception has occurred

during the later part of the intermenstrual interval. Thus, in the

former case the excess of boys is represented by the figures 37 : 12; in

the latter case the excess of girls is represented by the figures 79

(girls) : 65 (boys). These figures are explained by _Fürst_ on the

theory that in the human species conception during the period of

post-menstrual anæmia probably leads to an enormous excess of male

conceptions (owing to the fact that the unfertilized ovum is badly

nourished during the days just before conception); whereas in the later

part of the intermenstrual interval the better nourishment of the ovum

probably leads to the procreation of an excess of girls—hypotheses which

are based on a quite inadequate number of instances. _Fürst_ gives the

following table:

═════════════════╤═════════════════╤═════════════════╤═════════════════

NUMBER OF DAYS │ Number of boys │ Number of girls │ Boys and girls

BETWEEN REPUTED │ born. │ born. │ together.

END OF │ │ │

MENSTRUATION AND │ │ │

REPUTED │ │ │

OCCURRENCE OF │ │ │

CONCEPTION. │ │ │

─────────────────┼─────────────────┼─────────────────┼─────────────────

1│ 7│ 1│ 8

2│ 6│ 3│ 9

3│ 9│ 5│ 14

4│ 15│ 3│ 18

5│ 3│ 6│ 9

6│ 5│ 6│ 11

7│ 6│ 5│ 11

8│ 2│ 8│ 10

9│ 4│ 5│ 9

10│ 6│ 4│ 10

11│ 6│ 5│ 11

12│ 3│ 6│ 9

13│ 4│ 5│ 9

14│ 6│ 5│ 13

15│ 1│ 2│ 3

16│ 2│ 5│ 7

17│ 2│ 3│ 5

18│ 3│ │ 3

19│ 1│ 3│ 4

20│ 1│ 2│ 2

21│ 1│ 1│ 2

22│ 4│ 1│ 5

23│ │ 1│ 1

24│ 1│ │ 1

25│ │ 2│ 2

26│ 2│ │ 2

27│ │ 1│ 1

28│ 1│ 1│ 2

31│ 1│ │ 1

│ 102│ 91│ 193

═════════════════╧═════════════════╧═════════════════╧═════════════════

_Baust_ gives a report, based, he says, upon “thoroughly trustworthy

data,” furnished by personal friends, regarding 14 cases, which show, in

his opinion, that every conception occurring in a week after the

cessation of the menstrual flow leads to the birth of a girl; but that

when conception occurs on the fifth or sixth day after menstruation the

result varies as regard sex. _Swift_, from a report of 20 cases, draws

the conclusion that in the intermenstrual interval, boys, in the latter

part of the interval girls are conceived.

The influence of the strength of menstruation upon the determination of

sex has also been studied by the statistical method, starting with the

idea that menstruation, in proportion to its strength, affords on the

average a measure for the subsequent nutrition of the embryo, and this

nutrition is further supposed to determine the sex. _Düsing_ therefore

arranged the births occurring in the lying-in hospitals of Dresden,

Leipzig and Jena, according to the information given regarding

menstruation in the clinical history of each case; it appeared that when

menstruation was comparatively scanty, there was a greater excess of

boys than when menstruation was comparatively abundant. The actual

figures were the following:

═══════════════╤═══════════════════════════╤═══════════════════════════

│ Abundant menstruation. │ Scanty menstruation.

───────────────┼─────────────┬─────────────┼─────────────┬─────────────

Dresden │ 902│ 847│ 495│ 431

Jena │ 66│ 69│ 56│ 45

Leipzig │ 21│ 22│ 239│ 211

───────────────┼─────────────┼─────────────┼─────────────┼─────────────

Totals │ 989│ 938│ 790│ 687

Sexual ratio │ 105.4 │ 114.7

═══════════════╧═══════════════════════════╧═══════════════════════════

Here also we may append the figures obtained by _Düsing_ regarding the

births of foals at the Prussian stud-farms, which he regards as

supporting his view that by natural selection all animals have acquired

the faculty, whenever stronger demands are made upon their sexual

capacity, of procreating a larger number of individuals of their own

sex. In the tables we learn how many mares on an average a stallion had

covered in each year, that is, we learn how great were the demands made

upon the sexual capacity of the stallion in that particular breeding

stable in that year. The figures relating to the years 1859 to 1892 were

tabulated and averages were drawn with the following results:

═════════════════╤═══════════════════════════════════╤═════════════════

NUMBER OF MARES │ NUMBER OF FOALS BORN. │ Sexual ratio.

SERVED. │ │

─────────────────┼─────────────────┬─────────────────┼─────────────────

„ │ Colts. │ Fillies. │ „

60–70 │ 42,445│ 41,933│ 101.22

55–59 │ 56,511│ 66,226│ 100.49

50–54 │ 59,940│ 61,096│ 98.18

45–49 │ 57,077│ 59,216│ 96.39

40–44 │ 59,967│ 62,007│ 96.71

35–39 │ 38,348│ 40,181│ 95.44

20–34 │ 26,354│ 27,069│ 97.35

From these figures, which relate a very large number of instances

indeed, we learn that when greater demands are made upon the stallion,

more males are procreated. In fact, except for two slight divergencies,

the rise in the sexual ratio proceeds strictly _pari passu_ with the

increase in the number of mares covered.

I must, however, draw attention to the fact that this assumption when

applied to the human species, that the man on whom whose sexual capacity

especially extensive demands are made, procreates an especially large

number of male children, is not confirmed by the sexual ratio among the

offspring of polygamous marriages in which unquestionably greater

demands are made upon the husband’s sexual powers than is the case in

monogamic unions.

The reports of travellers of earlier days, to the effect that in

Oriental countries more girls are born than boys, have recently been

confirmed by several observers. _Campbell_ states that in the harems of

Siam the number of boys and girls born is equal. _Clarke_ states that

among the Mohammedan Indians more girls are born than boys. According to

_McLennan_ Indian experience teaches us that where polyandry prevails

male offspring predominate in numbers; but where polygamy prevails there

is, on the contrary, an excess of female infants. The following data

collected by _Goehlert_ from historical reports and from genealogical

writings, regarding the progeny of notable persons living in polygamous

unions, show certainly a large excess of female offspring over male:

│ CHILDREN. │ Sexual ratio.

„ │ Male. │ Female. │ „

Morocco: Muley │ 24│ 124│ 19.4

Scherif │ │ │

Palestine: │ │ │

Rehoboam, King │ 28│ 60│ 46.6

of the Jews │ │ │

Arabia: Imon of │ 14│ 74│ 18.9

Sana │ │ │

Turkey: nine │ 110│ 128│ 85.9

sultans │ │ │

According to _Tousenel_, love marriages give rise to more daughters than

sons, whereas among the offspring of conventional or compulsory

marriages, male children predominate. Further, among the offspring of

legitimate unions, the excess of males is greater than among the

offspring of illegitimate unions. A physician, _V. J. Cook_, maintains

that boys are procreated in the evenings (before midnight), but girls

during the early morning hours—at which latter time women are less

“impressionable” than during the evening hours.

_Düsing_, starting from the common belief that all animals have the

faculty, when there is a lack of individuals of one sex, of procreating

an excess of offspring of the sex which is deficient and thus of

restoring the balance between the sexes, maintains that numerous

factors, through the co-operation of which the sexual ratio is

regulated, act in temporal succession. He shows that the individuality

of the mother has an influence upon the sex. But this finds expression

through the qualitative constitution of the ovum; hence already before

fertilization there must exist a tendency toward the development of one

sex or the other—for example, younger ova tend to become females; older

ova, on the contrary, to become males. It has further been shown that

the individuality of the father, that is to say, the qualitative

constitution of the sperm, has an influence in the determination of sex.

Thus, by means of the influence of the sperm, the already-mentioned

pre-existing tendency of the ovum can in some instances be counteracted

and overpowered. The influences in the personality of the father and of

the mother, which during fertilization find expression in the

qualitative constitution of the sperm and of the ovum, respectively, can

thus bring about a resultant tendency, acting in one direction or the

other with varying force. Thus, after fertilization, we have this

resultant tendency toward the formation of a male or female embryo.

But, _Düsing_ continues, at this time the sex is not definitely

determined. The influence of the nutritive condition in which the

fertilized ovum finds itself has yet to make itself felt. This influence

on the determination of sex through the maternal nutrition, continues

(in the human embryo) for as long as three months, but even when the

reproductive organs of the embryo have definitely begun to diverge in

the direction of the masculine or the feminine type, as the case may be,

some nutritive influence, if it is sufficiently powerful, may yet turn

the balance in the other direction, so that a partial or complete

hermaphrodite results, a being uniting the characteristics of both

sexes.

Actual inheritance of sex, of which people used to speak, cannot, in

_Düsing’s_ opinion, possibly occur. The mode in which one sex or the

other develops is indeed inherited; but the decision which sex shall

develop does not depend upon inheritance, but is determined by the

co-operation of several outward influences. The qualities by which this

is effected are acquired by adaptation to general or special vital

conditions.

_Wilckens_ (“A study of the Sexual Ratio and of the Causes of the

Determination of Sex in Domestic Animals”) opposes the views of Düsing,

on account of the results of his own investigations, relating to the

births of 30,000 domestic animals. He formed the following conclusions:

1. _Locality_ (soil and climate) has an influence upon the sexual ratio

and upon the determination of sex in domestic animals, but this

influence is probably indirect only, being exerted through the

intermediation of the nutrition of the embryo _in utero_.

2. _The season_ in which the domestic animal is conceived affects the

sex; the hot season favours the production of males, the cold season

that of females; in the hot season, in general, the appetite and

nutrition of domestic animals diminish, whereas in the cold season these

increase.

3. Regarding the _male progenitor_, neither his age, nor his sexual

energy, nor the demand made upon that energy, nor the age of the semen,

has any influence upon the sexual ratio or the determination of the sex

of the offspring.

4. The age of the _female progenitor_ influences the sexual ratio and

the determination of the sex of the offspring in this way, that in

general, primiparæ and young mothers conceive a larger number of female

offspring. This influence of age may be referred to the fact that in

general young mothers nourish their offspring _in utero_ better than

older mothers.

5. The _nutrition of the fruit in utero_ influences the determination of

sex, speaking generally, in the following way, that better nutrition

favours the determination of the female sex, worse nutrition favours the

determination of the male sex.

6. In addition to the influence of nutrition of the fruit upon the

determination of sex, _other influences_, whose nature still remains

_obscure_, must also co-operate, because one and the same progenitor in

similar nutritive conditions does not always procreate offspring of the

same sex.

7. Owing to the operation of these _unknown influences_, prediction of

the sex of the offspring, and voluntary determination of the sex of the

offspring, remain impossible. All we can say is that there is some

probability that young and well-nourished mothers will procreate a

comparatively larger number of female offspring, whilst elderly and

ill-nourished mothers will procreate a comparatively larger number of

male offspring.

_II. Anatomical Investigations._

Of anatomical investigations and discoveries, those more especially

relating to the sex-relationships of twins and triplets have been

applied to the elucidation of the problem of the determination of sex.

The first and most important fact in this connection, one that is not

merely a rule confirmed again and again by anatomists and gynecologists,

but is further, as _Mayrhofer_ has demonstrated as a result of his

researches in _von Braun’s_ clinic, a “natural law,” is this, that twins

and triplets enclosed in a common chorion are invariably of the same

sex. The sex-identity of such twins has been referred to the similarity

of their nutritive conditions (_Leuckart_, _Ploss_), and more especially

to the communication between their bloodvessels; and an intimate

connection between these relationships and the determination of sex has

been believed to exist.

_Mayrhofer_, however, opposes this assumption by the following

deductions (“The Determination of Sex in the Human Species”); “Fœtuses

enclosed within a single chorion always possess a common placenta, in

which the blood-channels from both umbilical cords frequently, in the

case of twins perhaps invariably, communicate. It might therefore be

supposed that the sex-identity of embryos enclosed within a single

chorion is due to the intermixture of their blood in the placenta.

_Hyrtl_, however, describes a triplet’s placenta, in which, though all

three fœtuses were enclosed within a single chorion, the vessels passing

to the umbilical cord of one of the fœtuses were entirely distinct from

the vascular area common to the two other fœtuses; it is therefore

probable that in the case also of twins enclosed within a single chorion

there is not _necessarily_ any communication between their bloodvessels

in the common placenta. But even if it were proved that in the case of

twins enclosed within a single chorion their bloodvessels always do

communicate in the common placenta, we could not therefore infer that

the intermixture of the blood of the two fœtuses is the cause of their

sexual identity.

“For the intermixture of the blood of the two fœtuses in the common

placenta could never lead to a complete identity in the composition of

the blood of the two; it could only lead to a diminution of the

differences which would exist between the bloods if their placental

circulations were entirely distinct, and the similarity in the bloods

thus established could not be expected to do more than make it a general

rule that such twins or triplets should be of the same sex; but to this

rule exceptions might be expected to occur in certain cases, as when

hæmatopoiesis in the two (or three) fœtuses was very different, or when

the circulation through the intercommunicating bloodvessels was

interfered with through the pressure of fibrinous deposits—differences

between the bloods would then arise sufficient to cause differences in

sex (if identical composition of the bloods is presumed to be the cause

of the sexual identity).

“Experience teaches us that the existence of communicating vessels in

the placenta does not suffice to induce a close similarity of growth and

of the formation of the organs in twin fœtuses; nor does it prevent the

illness and death of one fœtus leaving the health of the other

undisturbed, although the communicating channels remain open; so that,

if we except acardiac monsters, it is correct to say that each fœtus

pursues a secluded life, uninfluenced by the life of its neighbour.

Acardiac monsters, on the other hand, always receive blood which has

already served for the nutrition of the normal fœtus, and the result of

this is an arrested development and a striking preponderance of

connective tissue in the acardiac twin. But notwithstanding the fact

that the failure of its own proper circulation (which is indeed rendered

possible by the existence of the communicating vessels in the placenta)

leads to its defective nutrition with a blood inferior to that supplied

to the normal fœtus, the acardiac monster is always of the same sex as

the normal twin.”

From these considerations _Mayrhofer_ rightly infers that the identity

of sex of two fœtuses contained in a single chorion, since it does not

depend upon the existence of communicating vessels in the placenta, must

arise from a developmental tendency already existing in the two germs at

the time of conception—or, in other words, that at the time of

conception their sex is already inalterably determined.

This conclusion with respect to the sex of twins contained in a single

chorion may very readily be extended to the inference that in the case

of all human fœtuses the sex is already determined at the time of

conception.

Another anatomical fact is that many twins are contained in a single

chorion for this reason, that they originate from two germinal vesicles

within a single ovum. It is an open question whether it is not possible

for two embryos contained in separate chorions to come to lie in a

single chorion through atrophy of the intermediate wall. If this is

indeed possible, the invariable identity of sex in the case of fœtuses

lying in a single chorion must lead us to agree with _Mayrhofer_ in

inferring that two ova lying within a single follicle, simultaneously

fertilized, give rise to embryos of identical sex.

_B. S. Schultze_ and _Ahlfeld_, as a result of the investigations

regarding twins, also came to the conclusion that the sexual identity of

twins depends upon their derivation from a single ovum. If, in

accordance with what has been said above, an explanation of the sexual

identity of certain twins is to be found in the fact that for such twins

there has been a single conception only, and hence the influence,

whatever it may be, by which sex is determined acts on both germs at the

same time—still the sexual identity of twins in general is remarkable

and has not yet been fully explained. The sexual identity in fact occurs

much more frequently than appears to correspond to the percentage of

twins derived from a single ovum. _Von Fricks_ examined the data

relating to multiple births in Prussia during the period of 1826 to 1879

and compiled the following table:

══════════════╤═════════════╤═════════════╤═════════════╤═════════════

Per Cent. │ Twins. │ Triplets. │Quadruplets. │Quintuplets.

Boys only │ 32.6│ 24.5│ 14.3│ 33.3

Girls only │ 30.3│ 22.5│ 19.4│

Boys and girls│ 37.1│ 53.0│ 66.3│ 66.7

│ 2 B. 1 G. │ 28.5│ │

│ 1 B. 2 G. │ 24.5│ │

│ │ 2 B. 2 G. │ 23.4│

│ │ 3 B. 1 G. │ 19.5│

│ │ 1 B. 3 G. │ 23.4│

│ │ │ 4 B. 1 G. │ 33.3

│ │ │ 3 B. 2 G. │ 33.3

According to _Ahlfeld_, of twin births in general, the ratio of those

with a common chorion to those with separate chorions is 1 : 8.15. If,

however, we wished to explain the frequency with which twins are of

identical sex from the occurrence of such twins derived from a single

ovum, we should expect to find a very different ratio, namely, 1 : 3.84;

that is to say, twins with a common chorion would have to be nearly

three times as common as they actually are. From these facts _Düsing_

endeavours to draw the conclusion that external conditions have an

influence upon the determination of sex, for very many external

conditions are identical in the case of twins; as, for instance, the age

of the father, the age of the mother, the nutritive conditions of the

ova and of the spermatozoa, the nutrition of the embryo, etc.—all of

these would influence both the twins in the same direction. A difference

in the sex of twins, on the other hand, might be due to two successive

fertilizations.

_B. S. Schultze_ has been led by his embryological studies to the

conclusion that there are male and female ova. Thus he believes that

sexually identical twins originate from a single ovum with two germinal

vesicles, thus assuming that a double fertilization of such ova is

possible. But since in such cases the sexes of the resulting twins are

always identical the spermatozoon can have no influence upon the

determination of sex, but the conditions leading to the development of

one sex or the other must pre-exist in the ovum—_i. e._, there must be

male and female ova.

That as a matter of actual fact in some cases the female progenitor

exercises an overwhelming influence on the determination of sex, and

that the opinion held by so many that this determination depends upon

the mother alone is sometimes supported by facts, is shown by the

incident recorded by _Darwin_ (“Descent of Man,” Vol. I.), that an Arab

mare was delivered seven times successively of a filly, never of a colt,

although she was covered by seven different stallions. On the other

hand, the circumstance, if it is not to be attributed to pure chance,

can also be explained by the constitutional vigour of this mare

(_Hensen_) without adopting the above hypothesis.

Recently _Upjohn_ has maintained that there are two kinds of

spermatozoa, male and female; the latter are the commonest, but the

former are the more energetic.

An interesting anatomical fact bearing upon this question has been

discovered by _M. Nussbaum_, namely, that in ascaris megalocephala the

reproductive glands are indicated already before the separation of the

germinal layers; and _Nussbaum_ suggests that this is also the case in

all animals, although the proof cannot be obtained in every instance.

_Semper_ has shown also in the case of some of the plagiostomata that

long before the beginning of the definitive development of the

reproductive organs, the apparently hermaphrodite embryo already

possesses at least the tendency toward the constitution of one sex or

the other. For in these animals, at a time so early that as yet the

reproductive glands exhibit no sexual differentiation whatever, the

sexes can nevertheless be distinguished by what appears to be a

secondary sexual character. In the female, namely, one ovary only is

developed; and very early indeed in the embryos destined to become

females we can observe an asymmetrical development of the two germinal

furrows. By this characteristic the two sexes can be distinguished far

earlier than it is possible to do so by the recognition of a

histological differentiation of the reproductive glands.

According to _Mayrhofer_ the prepotency of the male gives rise to the

procreation of an excess of males in this way, that physical prosperity

of the male probably leads to the generation of boys, whereas prosperity

of the female tends to give rise to the generation of girls. Moreover,

economizing of the semen by infrequent sexual intercourse tends to

originate offspring of the male sex. In this connection _Hensen_

remarks, apropos of the greater excess of male offspring among the Jews:

“We might ask whether, in consequence of the comparative sexual

continence of the Jews which demands a definite power of endurance on

the part of the ova, there may not be effected a certain selection of

the ova; and thus we may perhaps explain how it is that in this race an

exceptional vigour is somewhat more often to be observed than in other

races.” _Bock_ assumes that “thinner semen,” such as results from more

frequent sexual intercourse, favours the procreation of the female sex,

whereas when intercourse is less frequent a larger number of boys is

likely to be born. _Janke_ indicates as two important fundamental

principles of scientific physiology that, (1) sexual intercourse

represents as it were a contest between the two parties to the sexual

act as to which shall transmit his or her sexual influence to the child,

the victor in the contest determining the sex of the offspring, and (2)

that a crossed inheritance occurs, inasmuch as whichever progenitor

proves stronger in this contest transmits to the child the sex other

than his or her own. He therefore advises women who long to have a boy

to drink a glass of champagne before fulfilling their conjugal duties in

order to gain increased sexual vigour.

_Fiquet_ also expresses the opinion that when a vigorous, passionate,

and sanguine male progenitor has intercourse with a frigid and

phlegmatic woman there will be a preponderant tendency for the offspring

to be female; whereas, when the conditions are the opposite of these,

the male progenitor being phlegmatic and cold, the female on the

contrary sanguine, passionate, and ardent, the offspring will probably

be of the male sex.

In opposition to these opinions of _Fiquet_ and _Janke_, to the effect

that the temperament and the sexual vigour of the progenitors have a

determining influence in the origination of the sex of the offspring,

_Düsing_ insists that the quality of the reproductive products are alone

influential. _Düsing_ lays down the following proposition: “The greater

the scarcity of individuals of one sex is, the more extensive

consequently the demands made upon the sexual capacities of the

individuals of that sex, the more rapidly their reproductive products

are employed; and the younger these products therefore are when employed

the more individuals of their own sex will appear among the offspring.”

_Richarz_ believes, on the contrary, that the prepotency of the male

gives rise to the procreation of more girls; a mother of high

reproductive capacity will have more boys, one of less reproductive

capacity, on the other hand, more girls.

_Starkweather_ (“The Law of Sex,” London, 1883) states his view in the

proposition: “The superior parent produces the opposite sex;” and he

holds the quaint view that this superiority is displayed in certain

anatomical characters of the face of the progenitor. He endeavours from

the shape of the head and from the facial expression to deduce the

superiority of the male and the female progenitor respectively. A high,

square forehead, with prominent supra-ciliary ridges, constitutes,

according to _Starkweather_, one of the principal symptoms of this

superiority; important also are a strongly developed middle third to the

nose, narrow lips, etc. He declares that in families known to him the

possession of this Roman nose in the father is signalized by the

possession also of a large number of daughters, while a Roman-nosed

mother has many sons. The more the parents’ noses resemble each other

the more equal will be the distribution of the sexes among the

offspring. He connects this fact (!) also with the fact that the

possessor of the aquiline nose is the ruler of the family. Men of great

strength of character procreate chiefly daughters; women, on the other

hand, with a powerful character and a firm will bring into the world a

notable excess of boys. In the Southern States of the American union

_Starkweather_ found confirmation of his theory, since he observed there

that among the offspring of white fathers and coloured mothers there was

an excess of girls amounting to 12 to 15 per cent. Among the half-castes

of Java, the so-called Lipplapps, in the third generation girls only are

born, and these are sterile. The excess of girls in these cases depends

upon the superiority of the white father; this superiority is

transmitted to the few sons of the second generation, and these

therefore procreate girls only to constitute the third generation; the

latter are not powerful enough to bear children at all.

_Roth_ has revived the old view that one ovary provides the germs for

the male offspring, the other those for the female offspring. He

believes further that in the process of cohabitation the mechanical

impressions and stimuli received by one-half of the external genital

organs, reinforced by contact with and pulling on the pubic hair, are

transmitted through the pudic nerve and the hypogastric plexus to the

corresponding half of the vagina and the uterus, to the Fallopian tube

of that side and to the corresponding ovary. If, now, we can consider it

as established (?), that in the human female one ovary discharges male

ova only and the other female ova only, it seems to him that it is the

corresponding half of the external genital organs, when specifically

stimulated in sexual intercourse, and the consequently increased vital

activity in the pudic nerve and its connections with the hypogastric

plexus, that must be regarded as the organ by means of which sex is

determined. _Roth_ has also been informed by laymen that when for some

time they have procreated daughters only they subsequently procreated

sons, “when, having been accustomed to sleep on one side of their wife,

they adopted the practice of sleeping on the other.”

_Ricardi_ reports that in Modena the peasants say that a man whose wife

has hitherto had daughters only, must, if he wishes to have a son,

assume some other posture than usual in the performance of coitus.

_III. Experimental Investigations._

A considerable number of years ago, _Thury_ attacked the problem of the

determination of sex by the experimental method. In his series of

experiments he ascertained, using 29 cows, that in the case of 22 of

these, which were served early in their heat, the calves were without

exception heifers, while in the case of the remaining 7, which were

served late in their heat, the calves were equally without exception

bull-calves (_Thury_, “The Law of the Determination of the Sexes,”

Leipzig, 1863); in the record of these experiments no mention is made of

the age of the cows. _Thury_ concluded that the sex was determined

according to the fertilization of the ovum soon or late after its

liberation from the ovary; namely, that an ovum fertilized soon after

its discharge produced a female, whilst an ovum which had become

comparatively old before it was fertilized became a male.

_Thury’s_ sensational experiments gave rise to a succession of similar

experiments, made mostly by cattle-breeders, above all in agricultural

colleges and in stud-farms.

Some of these experiments were made in the agricultural colleges at

Proskau and Eldera. The cows, which according to _Thury’s_ views should

have been delivered of heifers, were served as soon as their heat was

observed (the heat lasted as a rule from 24 to 30 hours); these were

delivered of 5 heifers and 5 bull-calves (in Proskau) and of 3 heifers

and 5 bull-calves (in Eldera); the sexual ratio in these cases was

therefore normal. On the other hand, cows which were not served until

their heat had lasted for 20 hours were delivered (in Proskau) of 1

heifer and 4 bull-calves.

Further experiments (in Waldau) gave the result that cows served early

were delivered of 1 heifer and 1 bull-calf. In another series (in

Eldera) 9 cows served as soon as heat was observed (or, speaking

strictly, in from ½ to 1½ hours of this), gave birth to 7 heifers and 2

bull-calves.

Experiments made at the Royal Friedrich Wilhelm Stud-Farm gave the

following results: In the case of 20 mares, which if _Thury’s_ theory

had been correct should all have given birth to fillies, 11 only

fulfilled this expectation; but 10, on the other hand, were colts.

_Touchon_, in his experiments at Hohenhau, obtained 11 calves and 2

foals, exhibiting the sex expected in accordance with _Thury’s_ theory.

_Düsing_ made a compilation of the figures given in all the experiments

made to test _Thury’s_ theory, with the following results: Cows

fertilized early were delivered of 13 bull-calves and 29 heifers; mares

fertilized early were delivered of 10 colts and 13 fillies; cows

fertilized late were delivered of 5 bull-calves and 2 heifers.

_Gerbe_ made experiments on rabbits, putting the buck to some

doe-rabbits soon after the beginning of their heat, but to others as

late as possible in their heat. On examining the young in the horns of

the uterus, from the ovary downward, the distribution of the sexes was

found to be approximately equal.

Whilst _Coste’s_ experiments on a hen gave results contradictory to

_Thury’s_ theory, _Albini’s_ experiments, made also on the common fowl,

gave results in agreement with that theory. He found that the hens began

again to lay fertilized eggs 3 to 6 days after intercourse with the cock

(from which they had previously been kept separate); on the average, the

distribution of the sexes in the chickens hatched from these eggs was

approximately equal, with, however, a slight preponderance of cock

birds. On the ninth and tenth days after separation from the cock the

eggs laid were half fertilized and half unfertilized; on the twelfth day

after separation from the cock the unfertilized eggs were in a great

majority; but even as late as the eighteenth day after separation some

of the eggs laid were still fertilized. The fertilized eggs laid from

the tenth to the fifteenth day after separation when incubated produced

a great preponderance of hen birds.

We have to thank breeders for a large number of experiments, such as

those made by the breeder _Fiquet_, at Houston in Texas, who found that

a bull upon whose sexual capacities excessive demands were made,

procreated bull-calves exclusively; whereas in herds containing numerous

bulls there were found among the calves born a preponderance of heifers.

In thirty experiments on cattle _Fiquet_ always found that the larger

the number of cows a bull had to serve, and the longer they were kept in

service, the larger was the proportion of bull-calves among their

offspring. On the other hand, if certain cows had their sexual desires

first satisfied by a gelded animal and were then served by a vigorous

and lusty bull, an excessive proportion of heifers was born to these

animals.

_Janke_ obtained similar results in the breeding of sheep. In a report

made to _Düsing_ he states that in the early part of the lambing season

more ewe-lambs are born than rams; in the latter part of the lambing

season, on the contrary, more rams than ewes. The explanation he gives

is that at the commencement of the pairing the rams are fresh and lusty,

whilst later their potency is comparatively exhausted. In stud-farms,

according to the same observer, it is a familiar experience that the

most vigorous stallions serving a mare in the morning commonly procreate

a filly; but if later in the day they serve a second mare they almost

always procreate a colt. This, he thinks, finds its explanation in the

fact that the stallion, when he serves the second mare, is in a

condition of comparative sexual exhaustion, the more so because he

usually covers the first mare twice.

_Maritegoute’s_ breeding experiments at the sheep-farm of Blanc

(Haut-Garonne), on the other hand, gave divergent results. In the early

part of the pairing season, as long as the ram’s sexual powers were

completely unimpaired, he procreated more male than female lambs. But

when a few days later a great number of the ewes were simultaneously on

heat and the ram, owing to very frequent acts of intercourse, began to

be sexually exhausted, the procreation of female lambs was in excess.

But when, finally, this period of maximum demands upon the ram’s powers

was past, and the number of ewes on heat became once more small, the

procreation of male lambs in preference to female was again observed.

The data obtained by _Düsing_ from the Prussian stud-farms, in which,

when greater sexual demands were made on the stallions, more males were

procreated, have been already mentioned.

_Fiquet_ made interesting experiments on cows and believed that in this

way he was able to demonstrate the influence of nutrition upon the

determination of sex—to such a degree, indeed, that he believed it was

possible to breed calves of either sex at will. The following method

gave him positive results in more than thirty instances. He never had

the cow served by the bull at the first heat, but only at the second (if

a cow is left unserved when on heat, the heat recurs after an interval

of three weeks). The interval of three weeks was utilized in the

preparation of cow and bull for the copulatory act. If a bull-calf was

wanted the cow was supplied with the most invigorating fodder and was

kept on the richest pasture available. The bull, on the other hand, that

was to serve this cow was turned out to graze on the poorest pasture and

was given poor fodder. At the end of the three weeks, when the cow came

on heat for the second time, its sexual appetite was as intense as

possible, whereas the bull showed but slight inclination to the sexual

act. If the bull now served the cow a bull-calf was procreated. The

opposite procedure led to the procreation of a heifer. For this purpose

_Fiquet_ kept the cow on low diet during the interval between the first

and second heats, and had her first served by a castrated animal. When

in this way, and by the low diet, the sexual appetite of the cow had

been sufficiently diminished, it was served by a lusty bull, which for a

long time had not been put to any cow, and the sexual potency of which

had been increased to the uttermost by feeding it for several weeks on

the most invigorating fodder.

The results of these experiments, according to which the nutrition of

the parent-animals before the copulatory act has an influence upon the

determination of sex, is explained by _Düsing_ in this way, that

nutrition influences also the quality of the reproductive products.

“Poor nutrition gives rise to diminished functional capacity of the

genital apparatus. Thus, for example, the production of semen is

lessened. It can, in fact, hardly be replaced as quickly as it is used

up. This occurs when there is a lack of adequate means of subsistence,

and also when there is a lack of comparatively young males. In both

cases alike we trace the effects in the birth of an excess of males.

Converse conditions give rise to an excess of female offspring.”

Passing now to consider investigations made by physiologists, _Born_, at

the anatomical institute at Breslau, has endeavoured to solve the

problem of the determination of sex by means of experiment. He employed

for this purpose _rana fusca_, an animal with which positive results can

be obtained in a comparatively short period of time. He examined the sex

both of the frogs in the free state (165), and also of larvæ which he

had bred in specially arranged aquaria. Whereas among the frogs

developing in the open, the numbers of the sexes appeared to be

approximately equal (there was an excess of females amounting to 2 or 3

per cent.); among those bred in the aquaria there was an enormous

preponderance of females (96 per cent.). This remarkable result is

referred by _Born_ to the inadequate supply of nutriment in the case of

the larvæ bred by him (he fed them on hydræ and on putrefying frog and

tadpole meat); from an examination of the alimentary canal of tadpoles

caught in the open _Born_ ascertained that their normal food was the mud

of the pools in which they were hatched, containing infusoria,

radiolariæ, diatoms, algæ, etc. The accuracy of this explanation

appeared to _Born_ to be more convincingly shown by the results in the

case of one of his twenty-one aquaria. In this one alone the percentage

of males was as high as 28 per cent., and the tadpoles in this attained

the same size as those developed under natural conditions in the open,

whilst in all the other aquaria the tadpoles remained abnormally small.

This particular aquarium, owing to an oversight, had pond-mud on its

floor, whilst all the other aquaria were floored with clean sand.

_A. von Griesheim_ disputes _Born’s_ results and believes that the

latter, determining the sex of the tadpoles by means of a hand lens,

must have mistaken a great many female tadpoles for males. He himself,

by repeated enumerations of a large number of tadpoles (685), part

caught in the open and part taken from a large aquarium, found that the

ratio between the sexes in the case of _rana fusca_ was regularly 36.7

males to 63.3 per cent. females.

_E. Pflüger_ refers the divergence between _Born’s_ results and his own

and those of _von Griesheim_ not to any error made by _Born_ in the

diagnosis of the sex of the tadpoles, but to the fact that in the

latter’s aquaria the mortality of the male tadpoles was probably greater

than that of the females. _Pflüger_ endeavoured to ascertain whether the

concentration of the semen might have an influence in the determination

of sex. A quantity of frog-spawn was fertilized with concentrated semen,

taken direct from the seminal vesicles, and another quantity of spawn

was fertilized with diluted semen, obtained by making an aqueous extract

of the incised testicles. The ratio between the sexes in the case of the

two lots of tadpoles, which were kept in separate aquaria, proved,

however, to be mathematically identical. But another experiment showed

that the number of males was very different, according to the kind or

race from which the animals were derived. He therefore believes that for

the character of the development of the reproductive organs, the race of

the parent animals is determinative. There is very little likelihood of

being able to modify this inherited sexual ratio by means of outward

influences affecting the ova and the ripe semen prior to fertilization,

and just as little by means of a number of abnormal influences (change

of climate, of water, of nutriment, etc.) acting on the fertilized ova.

_Düsing_,—who in his work on “The Regulation of the Sexual Ratio” (Jena,

1884) most ingeniously advocates the thesis that all animals have the

power, when there is a lack of individuals of one sex, of procreating an

excess of individuals of this deficient sex, or, to put it in another

way, that an excess of one sex determines the procreation of an excess

of the other sex,—instituted experimental investigations regarding the

determination of sex in the following manner (in accordance with a

suggestion made by _Pflüger_): About ninety guinea-pigs were distributed

in two pens in such a way that in one pen there was a great deficiency

of males and a great excess of females, whilst in the other there was a

deficiency of females and an excess of males. Thus the sexual ratios in

the two stalls were opposed. In accordance with _Düsing’s_ theory,

therefore, more males should have been born in the first pen and more

females in the second pen. Every week each pen was examined once or

twice, the sex of the new-born young was ascertained, and they were

distinguished by small incisions in the margin of the ear. A week later,

when the young animals had developed a little further, they were

re-examined to make sure that no mistake had been made.

At first, in the pen containing the original excess of females, there

occurred a quite remarkable excess of male births. This, however, was

merely the result of chance, for soon the relationships of the sexes

among the new born was reversed, and thenceforward many more females

were born than males. But if all the births occurring in this experiment

are taken into consideration the number is still far too small to allow

trustworthy conclusions to be drawn.

_Düsing_ emphasizes the fact that such an experiment as this, in order

to furnish results worth consideration, must be continued until the

sexual ratio has become constant, so that it is no longer subject to

alteration by chance variations. If we assume that _Düsing’s_ theory is

false, the results obtained would be the following: In both the pens, in

that in which there was originally an excess of females and in that in

which there was originally an excess of males, the births, if observed

through a sufficient period, would present a definite sexual ratio which

would be the same in both the pens. But if the theory is well founded

the sexual ratio of the new born would vary in the two pens: in the

stall in which there had originally been a deficiency of males there

would be an excess of births of males over females; whereas in the pen

in which there had originally been a deficiency of females there would

on the contrary be an excess of births of females over males. _Düsing_

recommends that for such experiments even more fruitful animals, such as

rats and mice, should be utilized.

Institutes for pisciculture would also be extremely suitable for such

experiments in breeding for the determination of the matter under

discussion because, owing to the fact that in these animals

fertilization is effected outside of the body of the parents, a direct

examination of the ova and the semen used in the experiments can be

undertaken, and the fertilization can be made to occur under conditions

subjected to various alterations; also we can employ the roe and the

sperm of fishes whose age, life history, weight and size are accurately

known.

Much attention has recently been paid to the theory of _Schenk_, based,

as he states, upon numerous experiments regarding the influences by

which sex is determined. This observer also starts from the principle

that ovulation is not independent of the influences of nutrition and

metabolism. He believes that in the cases in which combustion in the

body is effected in such a manner that remnants of unconsumed

substances, still capable of heat-production, make their appearance in

the urine, the ovum of the human female in process of formation is not

so far advanced in its development as it is in cases in which the urine

is entirely free from sugar, or at any rate is free from any

demonstrable traces of the presence of this body. In the former case we

shall find that the ovum is not only less mature, but also that it is

presumably less well nourished. In his view such an ovum is less

completely endowed in respect of the indwelling qualities and forces of

its protoplasm, and it appears for this reason to be adapted only for

the development of a female individual. But when, on the contrary, in

the maternal individual, all the substances formed in and assimilated by

the organism have undergone combustion so completely that there is no

sugar in the urine, not even in the minutest discernible traces, the

maternal body is in a condition suitable for the development of an ovum

adapted to become a male individual. From these inferences, weak though

the chain of argument is, _Schenk_ draws the conclusion, that by the

regulation of the nutritive material supplied to the organism, and by

the suitable choice of that material, we are to a considerable extent

enabled to support an ovum in its process of maturation in such a manner

as to cause it to develop into a male individual.

The nutritive material selected for this purpose must be of such a

nature that the elimination in the urine of even the minutest quantities

of sugar may be prevented; the urine must appear free from sugar even

when the phenyl-hydrazine test is employed. Thus in every case in which

we wish to influence a woman’s nutrition in such a way as to lead to the

procreation of a male individual we must above all ascertain whether, in

the woman in question, the normal quantity of sugar is present in the

urine. If after the most careful examination no trace of sugar can be

found in the urine, and if reducing substances are present in this

excretion in abundance, no change need be made in the diet, and all we

have to do is to recommend that the requisite fertilization should be

effected as soon as possible, since there is every probability that in

this condition the embryo will prove to be of the male sex. But when, on

the other hand the “normal” quantity of sugar is present in the urine,

or when even traces only of that substance can be detected, it is

necessary by changes in the diet to cause the disappearance from the

urine of every trace of sugar, and at the same time to bring about the

appearance in that fluid of an abundance of reducing substances.

_Schenk_ claims by the experiments he has made along these lines to have

obtained results which show that it is possible in this way to influence

the determination of sex.

His method is to nourish the mother mainly on nitrogenous materials and

fat, and to give in addition only so much carbohydrate as is necessary

to prevent the absence of this from being seriously felt. This diet

should be continued for a considerable period, at best for two or three

months before the fertilization is effected. After conception also, the

same diet should be continued. In such a manner we are able in certain

cases to bring about the procreation of male offspring. On the other

hand, the desire for the procreation of female offspring remains one

which as yet we have no direct means of fulfilling.

These vague experiments and ill-grounded theories of _Schenk’s_ do not,

as a matter of fact, constitute an important advance in the theory of

the voluntary determination of the sex of the human offspring. What in

reality are the decisive influences in the determination of sex, and how

the final impulsion in one direction or the other is actually effected,

remain altogether obscure. Prediction of the sex of the offspring, and

the voluntary procreation of male or female infants, remain problems for

the solution of which the most essential data are still lacking.

_Ernest Hæckel_ writes regarding _Schenk’s_ theory: “This important

‘discovery,’ which at the time of its first announcement attracted

throughout the world an attention rarely given to true scientific

advances, has now dwindled to the incomplete demonstration that the

nutritive condition of the mother exercises a certain influence upon the

determination of the sex of the child. But we knew this much a long time

ago. _Düsing_ and others, partly by physiological experiments and partly

by statistical demonstrations, had shown that changes in the quantity

and the quality of the nutriment supplied to either parent is capable of

influencing the procreation of boys or girls. But if what _Professor

Schenk_ maintains were really true peoples living chiefly upon meat (as,

for instance, in the pampas of South America) should have an

exceptionally large proportion of male offspring; whereas those living

mainly on a proteid-free diet (on meal, sugar, and other carbohydrates),

should have an exceptionally large proportion of female offspring (as,

for example, the rice-eating Indian and Mongolian nations). But this is

by no means the case. And many other well-known facts are likewise

opposed to the ‘epoch-making’ theory of _Schenk_. Whether the fertilized

ovum develops into a boy or a girl, depends, I am convinced, upon far

more complex, and to a large extent still entirely unknown,

physiological causes. The final judgment upon the ‘Schenk theory’ must

be, ‘Much Ado About Nothing.’”

Our exposition of the present standpoint of the doctrine of the

origination of sex in the human species, has, in fact, shown that

hitherto by statistical work, nor by anatomical investigations, nor,

finally, by the experimental method, have results been obtained which

render it possible to predict the sex of the unborn infant. And even in

respect of the study of those influences which exercise a determining

influence upon the origination of sex, no positive, indisputable

conclusions have been reached. We can only say it appears probable that

there exist _several_ causes of the determination of sex the

_co-operative_ action of which proves effectual. Not in the ovum alone,

nor in the spermatozoon alone, but in the reciprocal influence they

exert one upon the other in the act of conception is sex determined. In

the latter connection the relative and absolute ages of the progenitors

appear to have a certain influence in the determination of the sex of

the embryo; of importance also is the greater or less demand made upon

the sexual capacity of the begetter; of influence too is the time at

which the ovum is fertilized after its discharge from the ovary. It

appears to be fairly well established that when the husband is at least

ten years older than the wife, while the latter is at the age at which a

woman’s reproductive powers are at a maximum, more boys are conceived

than girls (_Kisch_); also that one of the progenitors upon whose sexual

capacities the greater demands are made, tends to procreate an excess of

individuals of his or her own sex (_Piquet_, _Düsing_); and, finally,

that intercourse a considerable time after the cessation of the

menstrual flow (in the second week of the intermenstrual interval or

later) is favourable to the procreation of a male infant (_Thury_,

_Hensen_). The influence of nutritive conditions in the determination of

sex is less clearly established.

Statistical evidence has proved beyond dispute that given a sufficiently

large number of instances in varying conditions the sexual ratio is 106,

and this fact suggests that the determination of sex is dependent upon

the interaction of two influences operating in opposite directions

within narrow limits, in such a manner that the chances of the birth of

a male infant preponderate over the chances of the birth of a female

infant in the proportion of 106 to 100. In elucidation of this fact

_Hensen_ makes the following comparison: “Let us imagine a balance the

beam of which has two arms of equal length; from the two extremities of

this beam two balls of nearly equal weight begin to roll toward one

another; if one ball rolls more quickly than the other, if one is

lighter than the other, or if one starts to roll before the other, the

opposite end of the beam will sink. The three influences are variously

distributed; one influence may reinforce another, or may counteract

another; but a decisive sinking of one end of the beam will always

ultimately ensue. A minimal shortening or lightening of one arm of the

balance will make the chance that the other arm will descend

correspondingly greater.”

The sexual life of woman in its physiological, pathological and hygienic aspects · 第 66 / 100 题