differently in the presence of unlike blood
streams. As to the greater average weight of the male brain, this is
true of the whole body. Brain weight, either absolute or relative to
body weight, is not positively known to be in any way correlated (in
normal people) with mental capacity.

A library might be stocked with the vast literature devoted to
summarizing and cataloguing sex differences; and most of it would be
useless from the standpoint of sociology. Unaccompanied by the
criticisms a biologist would have to make on the method of their
ascertainment and validity, not to mention their significance, such
lists can easily do--and probably have done--more harm than good. One
simple and reasonable criterion would reduce this catalogue to fairly
modest proportions, so far as social science is concerned: _Which ones
have an obvious or even probable social significance?_ Over and above
that, while such contrasts may be of speculative interest, they lead
imaginative people to argue from them by analogy and thus cloud the real
issues.

What are the outstandingly significant sex differences which application
of the above criterion leaves? (1) A less active and more uneven
metabolism of woman; (2) Associated with this, less physical strength on
the average--hence an inferior adaptability to some kinds of work,
resulting in a narrower range of choice of occupation, disadvantageous
in competitive society; (3) But the one fundamental difference, to which
all the others are as nothing, is the specialization of the mammalian
female body and metabolism to furnish the intra-maternal environment
(approximately nine months in the human species) for the early
development of the young and lactation for some months afterward.

This last may be said to include the former two, which were arbitrarily
placed first because they are always in evidence, whether reproduction
is undertaken or not. This takes us out of cell and endocrine biology
and into the general problem in group adjustment to environment which
that specialization entails.

BIBLIOGRAPHY FOR CHAPTER III

1. Goldschmidt, R. Experimental Intersexuality and the Sex Problem.
Amer. Naturalist, 1916. Vol. 50, pp. 705f.

2. Goldschmidt, R. Preliminary Report on Further Experiments in
Inheritance and Determination of Sex. Proc. Nat. Acad. Sc, 1916.
Vol. II, No. 1, pp. 53f.

3. Goldschmidt, R. A Case of Facultative Parthenogenesis. Biol.
Bulletin, 1917. Vol. XXXII, No. 1, p.