A DIFFERENCE IN THE METABOLISM OF THE SEXES 59
in the processes of menstruation, gestation, and lactation) the constructive tendency still asserts itself, and a slight access of growth and vitality results to the organism.
DIFFERENCE IN BRAIN WEIGHT FROM TWENTY TO SIXTY YEARS.
Author
Weight Number of women's
of brains brains
Broca (revised list of Wagner),
77 1,244
Welcker, -
258
,247
Peacock (Scotch), -
- 89
,275
Boyd (English), -
370
,221
Thurnam (various),
- 536
,233
Broca (registers),
5i
,195
Bischoff,
272
,227
Broca-Bischoff-Boyd,
693
,211
FROM SIXTY TO
NINETY YEARS
Broca (revised list of Wagner),
32
,203
Welcker, -
99
,175
176
Thurnam (various),
422
,1 / \j ,178
Broca (registers),
85
,111
Bischoff,
50
,157
Difference from man
126
M3
142
133 138 164 141 150
123 125
158 150
Organic development in general, and social structure and function in particular, are conditioned by this fundamental con- trast in the metabolism of the sexes. Sex is, indeed, an expres- sion of this difference, or, more exactly, it is this difference, and in the principle of sex lies the possibility of all higher develop- ment. Asexual organisms never rise above a low type of devel- opment because variation, on which development depends, is furnished only by the union of different organisms. The prin- ciple of sex is, therefore, to be recognized as the beginning of those changes which, controlled by natural selection, end in the development of organs of locomotion, prehension, ingestion, and digestion, fitting the organism increasingly for the struggle for food.
The struggle for food is, however, anti-social, or at best unsocial, in its beginning, and we must seek the principle of social
