vidual is already determined as
early as any other of his or her characters, though the realization of
the potentialities of that sex may be much modified by nurture, as in
the contrasted cases of the queen bee and the worker bee. Children,
then, are already of one sex or other, and though our business in the
present volume is not childhood of either sex, a few points are worth
noting before we take up the consideration of the individual at the
period when the distinctive characteristics of sex make their effective
appearance.

Despite the abundance of the material and the opportunities for
observation, we are at present without decisive evidence as to the
distinctiveness of sex in any effective way during childhood. Here, as
elsewhere, we have to guard ourselves against the influences of nurture
in the widest sense of the word; as when, to take an extreme case, we
distinguish between the boy and the girl because the hair of the one is
cut and of the other is not. The natural, as distinguished from the
nurtural, distinctions at this period are probably much fewer than is
supposed. It is asserted--to take physical characters first--that the
girl of ten gives out in breathing considerably less carbonic acid than
her brother of the same age, thus foreshadowing the difference between
the sexes which is recognized in later years. If this fact be critically
established it is of very great interest, showing that the sex
distinction effectively makes its presence felt in the most essential
processes of the body. But we should require to be satisfied that the
observations were sufficiently numerous, and were made under absolutely
equal conditions, and with due allowance for difference in body-weight.
They would be the more credible if it were also shown that the number of
the red blood corpuscles were smaller in girls than in boys in parallel
with the difference between the sexes in later years.

Children of both sexes have fewer red blood corpuscles in a given
quantity of blood and a smaller proportion of the red colouring matter,
or haemoglobin, than adults. Women have very definitely fewer red blood
corpuscles than men, and a smaller proportion of haemoglobin, and their
blood is more watery. 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