e factors. Davenport has concluded that there are two double
factors for black pigmentation in the full-blooded negro which are
separately inheritable. The determinants of the red and yellow have
still to be worked out.

The moistness of the skin, as perspiration, depends upon the number
and activity of the sweat glands. It varies with the water content of
the body, the state of the vegetative nervous system, and the body
temperature. Thus the skin of the hyperthyroid and the subadrenal
is soft and moist, because of their antagonistic effects upon the
sympathetic system. The subthyroid and the hyperadrenal have dry
and harsh skins for the same reason, if no other glands intervene.
However, in both of the latter, if there is a persistent thymus, the
skin will retain the bland quality of adolescence.

There is a curious variation among the different internal secretion
types in the reaction of the skin to stroking. When the skin,
especially the skin over the shoulders, the breasts and the abdomen,
is stroked with some blunt object, the blood vessels react either by a
greater filling up or emptying of themselves. The latter occurs most
regularly in the subadrenal types, the former in the hyperthyroid.
Both forms of reaction run parallel to the different check or drive
effects of the vegetative apparatus. With too much drive, that is, too
much thyroid, there is the flushing reaction; with too little check,
that is, with too little adrenal, there is the whitening. These
differences probably explain the emotional reactions of the face. In
anger, for example, some people become a dead white, others a fiery
red. Whether one will do one or the other may depend upon the relative
predominance of the thyroid or of adrenal in the individual.

In the distribution of fat beneath and throughout the skin all of the
endocrine glands appear to have a voice. The typically hyperthyroid
and hyperpituitary individuals tend to be thin, as well also as those
who have well-functioning or excessively functional interstitial
cells. In all of these the administration of the respective internal
secretions increases the burning up of material in the body, and all
of them have a higher rate of tissue combustion than their confreres,
with a subthyroid or subpituitary keynote in their cell chemistry, or
with insufficient interstitial cell action. Generally the latter have
a very dry skin, the former a moist skin. With delayed involution of
the pineal,