NUMBERS OF Males and FEMALES IN The Native White of NATIVE PARENTAGE Population of the UNITED STATES

different in the two sexes. Ten years ago the chromosome count in the sperm was stated as forty-seven, in the ovum as forty-eight. It is now known that both have forty-eight but the sperm contains one of ordinary rod shape (now called X) while the second is spherical (called Y). In the reduction division in the female, twenty-four of these chromosomes are thrown out and the final ovum is larger in size but contains only twenty-four chromosomes, all of the X type. In the male after the reduction division all the sperms are functioning but one-half contain the X chromosome, one-half the Y. Depending on which of these unites with the ovum, a boy or girl develops. Since all the body cells result from these germ cells it follows that there is a certain difference in every cell of the body of the two sexes.

The process of making a man or a woman is well on its way at time of birth, yet it is far from complete. There is evidence that the hormones produced by the germ cells do

much to determine the later character of boys and girls. There is reason to believe that the endocrine glands are extremely important for the normal development of the individual. Whether there is any difference in the equipment of the two sexes as regards these glands is almost wholly unknown and it is a field monopolized by quacks rather than students.

Physical Differences between the Sexes

The infant begins to grow and the rate of growth varies with the sex. In England and America at least, "until the age of nine, boys are above girls in height and weight; at nine and ten are slightly under in height; at ten slightly under in weight; at eleven materially lower in height and weight; at

fourteen boys are slightly heavier than girls; at fifteen taller than girls. In other words the pubertal acceleration of growth occurs about three years earlier in girls than boys." 4 The preceding table shows the differences of height and weight of school children at Battle Creek, Michigan. 5

The period of growth over, the most obvious physical differences between men and women are (1) relative size and strength, (2) proportions of the body, (3) distribution of hair on body, (4) voice.

In all races of men, man appears to average taller, larger and stronger than woman. These differences seem less marked in the more primitive groups and more marked among civilized peoples. This suggests that to some extent they depend on differences in daily life. Our college men are about 68 inches tall, college women 63. For this difference heredity is our only explanation. The striking superiority of college men in athletics is in part an index of activities, but only in part. Structural differences are involved.

The proportions of the body differ much as between the sexes. The arms and legs of the man are relatively longer than those of the woman. The thigh of the woman is much shorter and of larger girth and is set at a different angle. The most striking difference is in the shape of the pelvis, which in woman is large and broad thus making possible the bearing of children with the relatively large heads characteristic of infants. This is a distinctly human trait for it is found nowhere else in the animal kingdom. This pelvis affects woman's carriage of the body. Man's skull is heavier, with larger frontal sinuses and more pronounced ridges over the eyes and nose. An expert would rarely mistake a woman's skull for that of man.

There is no special difference in the hair of the head though woman at times seems to have more and to be less inclined to baldness. Man's beard is very characteristic, but this varies with the race and is never found on the woman

though she often preserves the early coating of down-the lanugo.

The changes in the boy's voice at puberty is universally known. Due to the growth of the larynx, his voice becomes deeper and stronger.

There are other differences not always apparent. Possibly one of the most significant of these is in the blood. All the observers seem to agree that the blood of woman contains fewer red corpuscles and that its specific gravity is lower.

In males the specific gravity is about 1,066 at birth, and falls during the subsequent two years, being about 1,050 in the third year; thence it rises till about seventeen years of age, when it is about 1,058. It remains at this height during middle life, and falls slightly in old age.

In females the specific gravity, starting at about 1,066 at birth, falls in infancy, as in males, to about 1,049 in the third year. Thence it rises till the fourteenth year, when it is about 1,055.5. Between seventeen and forty-five years of age it is lower than at the age of fourteen, and is about three degrees lower than in

men.

It will be seen that it is at puberty that the sexual differences become marked. . . . In old women the specific gravity rises.

...

The pulse of woman beats about ten times a minute more than that of man.

The amount of carbon consumed in the male body rises at puberty to about double the amount consumed in that of the female. Women seem to need less air than men.®

There is a considerable body of evidence justifying the widespread belief that woman is essentialy anabolic, i. e., tends to store up strength and energy; while man is katabolic, i. e., tends to dissipate his energy. Woman is more likely to become fat. "Statistics show that woman is more susceptible to many diseases, but in less danger when attacked, because of her anabolic surplus and also that the greatest mortality in

woman is during the period of reproduction, when the specific gravity of the blood is low and her anabolic surplus small." The biologist would say that woman needs this reserve to meet the demands of childbearing-a burden utterly unknown to the male.

Ploss, after a long review of the evidence, comes to the conclusion that:

The bodily needs of women are much less than those of men; they eat and drink less; they breathe less and withstand suffocation better, it is believed. All troubles, at least those which slowly develop and persist, all deprivations, they bear much better than men, in part at least, much better than one would expect considering their physical powers. They better withstand loss of blood and persistent pains. Even the greater sensitiveness of the nervous system, because of which many trifling disturbances cause lasting after effects, appears to favor the rapid and harmless dissipation of the upsetting experience. Thus they reach old age, often, under unfavorable circumstances though the cases of extreme old age reaching well into the second century are almost always men.8

Of the effects of industry on the two sexes a very competent English student says:

In these days we find men and women of unequal powers of resistance crowded into factories and trying to keep pace with machinery. . . . Resistance to fatigue is not only a matter of health and physique but of sex as well. Woman is physiologically handicapped and therefore goes down more readily. . . Data concerning some aspects of fatigue problems are unobtainable because, notwithstanding what has been said, there are many women who are not only physically equal to men, who work as hard and bear fatigue just as well as, if not better than, many men. This applies rather to the few than to most women. In cotton mills in Switzerland, where both sexes are employed, Schuler and Burckhard found the relative morbidity of men and women in the spinning department 100: 13. The duration of sickness is higher for women than men. Even where the morbidity tables of Insurance Societies show men to