systems upon the life cycles of the sexes are quite obvious. What we
call the "quantitative theory of sex" has, besides a place in exact
science, an interesting relation to the history of biological thought,
especially as applied to society. It is thus in order to state as
clearly as possible what it now is; then, so that no one may confuse it
with what it is not, to run over some of the old ideas which resemble
it.

Experiments with transplanted sex glands, with sex-gland extracts
(testicular and ovarian) and the observation of infusions of a male-type
blood-stream into a female body, as occurs in nature in some cattle and
in the so-called human "hermaphrodites," indicate a gross chemical
difference between the respective determiners for femaleness and for
maleness. So the chemicals involved, though not yet isolated, must be
presumed to be _qualitatively_ different, since they produce such
different results.

But such experiments also indicate that both determiners must be present
in some proportions in every individual of either sex. The basis for
both sexes being present, the one which shall predominate or be
expressed in the individual must depend upon the _quantitative_ relation
between the determiners which come together at fertilization. The
quantitative theory merely means that this predominance of one factor or
the other (maleness or femaleness--Gynase or Andrase) is more pronounced
in some cases than in others.

In brief, then, the quantitative theory of sex is merely the most
reasonable explanation of the known fact that intersexes exist--that is,
females with some male characteristics, or with all their characters
more like the female type than the average, and _vice versa_. Laboratory