lies back of them; i.e., there are two general types of secretory
balance, one for males and one for females. Not only are the secretions
from the male and the female sex glands themselves quite unlike, but the
whole chemical system, balance or "complex" involved is different.
Because of this dual basis for metabolism or body chemistry, centering in
the sex glands, no organ or cell in a male body can be exactly like the
corresponding one in a female body.

In highly organized forms like the mammals (including man), sex is
linked up with _all_ the internal secretions, and hence is of the whole
body.[3] As Bell [2, p.5] states it: "We must focus at one and the
same time the two essential processes of life--the individual metabolism
and the reproductive metabolism. They are interdependent. Indeed, the
individual metabolism is the reproductive metabolism."

Here, then, is the reason men have larger, differently formed bodies
than women--why they have heavier bones, tend to grow beards, and so on.
The sex glands are only part of what we may call a well-organized
chemical laboratory, delivering various products to the blood, but
always in the same general proportions for a given sex. The ingredients
which come from the sex glands are also qualitatively different, as has
been repeatedly proved by injections and otherwise.

Each of these sex types, male and female, varies somewhat within itself,
as is true of everything living. The two are not so far apart but that
they may overlap occasionally in some details. For instance, some women
are larger than are some men--have lower pitched voices, etc. The whole
bodily metabolism, resting as it does upon a chemical complex, is
obviously more like the male average in some women than it is in others,
and _vice versa_. But the average physical make-up which we find