( Originally Published 1918 )
A great deal of attention, both scientific and other, has been given to the subject of the predetermination of sex. The majority of people feel that they would like to have the power to say to which sex their child should belong. In the case of ruling families and those with great wealth to dispose of, it has generally been considered desirable to have the first child a boy and, if any one had been able to discover an absolutely certain method for determining beforehand the sex of the child that was to be born, that individual would probably have coined a fortune that would be the envy of even a Rockefeller. A good many persons have thought that they had a sure way of fixing the sex of the child before it is born; but although these methods seem sometimes to have produced the desired result further experimentation has as a rule proved them to be unreliable.
The law of chance must be taken into account ,whenever one attempts to prove the trustworthiness of any theory. It may be quite true that a certain couple followed a prescribed regime for producing a child of the male sex and the infant born to them may have been a boy. Nevertheless, this does not prove that the method pursued was a cause of the result. The child might have been a boy in any case. If the same method, used upon another occasion or by other individuals, should fail once to produce the desired result, the method would thereby be proven to be not absolutely infallible.
In the first place, it is interesting to consider the relative number of the sexes, not only in the early years of life but also in the later age periods. The study made of this subject seems to assure us that a few more males are born into the world than females. The average in civilized countries during a long series of years is about 105 boys to 100 girls. The fundamental difference between the sexes is clearly shown even at this early period of life in the relative vitality of the two sexes. As the female is the constructive half, tending always to remain more or less passive and, there-fore, able to store up material for future use, so we are not surprised to learn that female infants are more tenacious of life than are male children. They more easily resist the diseases incident to infancy and childhood, so that at the age of puberty it is found that there are a few more girls than boys. This difference increases until the years of maturity, when we find that there are about 105 adult females to about 100 adult males.
This difference between the vital resistance of the boys and girls in early childhood is known practically to all who have the care of infants. Every mother of a family realizes the greater difficulty which she experiences in bringing her boys to maturity than in rearing her girls. Of course, it is easy to be seen that this added vitality is needed by woman in order to enable her to pass through the increased demand made upon her system by the process of gestation and birth. In spite of the dangers incident to maternity, the number of women markedly increases in proportion to the number of men throughout the years of life, these dangers being offset among the male population by the effects of war, lust, narcotism, machinery, exposure to inclement weather and similar exigencies. In an ideal state of society the number of men and women would be aproximately equal, thus insuring the possibility of a mate for every human creature.
There have been many superstitious beliefs in regard to sex determination. Some have thought that the organs on one side of the body produced female germs, the organs on the other side of the body produced male germs. Some have thought that it depended upon the comparative vitality of the germ cells, those of more vitality resulting in males and of less vitality in females. This doctrine, however, is contrary to the proven facts of seat differences. Some have thought it depended upon whether the husband was older than the wife, or whether one parent was more vigorous then the other. Some have thought that it depended upon the age of the mother.
One of the theories which has seemed to have more possibility of truth in it than these superstitious beliefs has pointed to the differences of sex as being determined by the abundance of the food supply. For example, it is known that more males in proportion to the number of females are born immediately following a war than at other periods. Some have claimed that this was because of the lessening of the food supply, due to conditions resulting from the lessening of the productivity of a nation as a result of the great number of workers that have necessarily been called into the war service. Those who believe in this theory also point to the well-known method by which bees develop workers (females) by giving them a larger food supply than is given to the drones (males) . The theory, however, has never been satisfactorily proven.
A much more probable theory seems to be that known as Thury's law, because it was first announced by a veterinary surgeon of that name at the Academy of Geneva. He studied the subject of sex determination while engaged in raising horses, cattle and other domestic animals. His conclusion was that sex is determined practically at the time at which the ovum is impregnated. He seemed to establish the fact that if fertilization occurred early in the fertile period the resultant offspring would be female. Another investigator put forth his theory as follows : "Sex depends upon the degree of ripeness of the female ovum at the time of its fecundation. If an ovum has reached the highest degree of' ripeness when impregnated, a male is sure to result." It is apparent that this Iast conclusion is based upon the belief that the male, both structurally and functionally, is more perfect than the female and must develop, therefore, from the more mature and complete ovum. According to this, if impregnation occurred immediately after the close of a menstrual flow—when, as a rule, the ovum is not fully matured—the result will be a girl ; but if, through a high nutritive condition of the mother, the ovum be fully ripe at the time of fertilization, the result will be a boy.
It is particularly interesting, in view of the above, to turn to a recent study conducted by a German scientist which appeared in a medical journal in September, 1916. This scientist has been charting data obtained by comparing the date of a soldier's brief furlough with the pregnancy of his wife. These charts demonstrate that conception was most likely to occur when the soldier reached home during the first days after cessation of the menses. The probability of conception then grew progressively less until al-most constant sterility was the rule for the woman during the days preceding the next menstruation. For the purpose of seeking to discover the laws predetermining the sex of a child, he divided the inter-menstrual period into three phases: one, from the first day of menstruation to the ninth day; two, from the tenth day to the fourteenth day; and, three, from the fifteenth to the twenty-second day. (The remaining six days are not considered as the woman may be regarded as sterile during this phase) . He obtained data along these lines in eighty cases ; the pregnancies dating from the first period gave thirty-seven boys and seven girls; the second period, four boys and eight girls ; and the third period, three boys and twenty girls. This would tend to prove that the male resulted from the unripe ovum which would accord with our present understanding of the law of sex itself.
My own opinion in reference thereto has been guided to a certain extent by the laws of utility, and in explaining this theory to audiences I have had various men vouch for its accuracy as a result of their own experience.
According to this theory sex is determined to a large extent by the force of attraction.
If the husband's affection for the wife is stronger than the wife's for the husband, then the child will be a girl. If conditions are re-versed, the wife feeling the attraction most strongly, the child will be a boy.
Under this theory you can, to a certain extent, account for the large number of boy babies born during or following war. The husband's attraction for the wife under such circumstances is greatly enhanced, not only because of the heroic character of his soldier life, but to a certain ex-tent because "absence makes the heart grow fonder."