According to one authority this difference in the
haemoglobin can be observed from the ages of eleven to fifty, but not
before. The specific gravity of the blood is found to be the same in
both sexes before the fifteenth year. Thereafter, that of the boy's
blood rises, and between seventeen and forty-five is definitely higher
than in women of the corresponding age. It thus seems quite clear that,
as we should expect, these differences in the blood, which are
certainly, as Dr. Havelock Ellis says, fundamental, make their
appearance definitely at puberty--a fact which supports the view that
fundamental differences of practical importance between the two sexes
before that age are not to be found. Careful comparative study of the
pulse of children is hitherto somewhat inconclusive, though it is well
known that the pulse is more rapid in women than in men.
On the other hand, it seems clear as regards respiration that as early
as the age of twelve there are definite differences between the sexes.
Several thousands of American school children were examined, and between
the ages of six and nineteen the boys were throughout superior in lung
capacity. The girls had almost reached their maximum capacity at the age
of twelve, and thereafter the difference, till then slight, rapidly
increased.[6] It appears that from eight to fifteen years of age a boy
burns more carbon than a girl, the difference, however, being not great.
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