446 ANNUAL REPORT SMITHSONIAISr INSTITUTION", 1919. 
of skin, and character of hair — all of them marks of race. Wlien 
we compare the three chief racial types of humanity — the Negro, the 
Mongol, and the Caucasian or European — we can recognize in the 
last named a greater predominance of the pituitary than in the other 
two. The sharp and pronounced nasalization of the face, the tend- 
ency to strong eyebrow ridges, the prominent chin, the tendency to 
bulk of body and height of stature in the majority of Europeans, 
is best explained, so far as the present state of our knowledge goes, 
in terms of pituitary function. 
There is no question that our interest in the mechanism of growth 
has been quickened in recent years by observations and discoveries 
made by physicians on men and women who suffered from pituitary 
disorders, but that a small part of the body could influence and regu- 
late the growth and characterization of the whole was known in 
ancient times. For many centuries it has been common knowledge 
that the removal of the genital glands alters the external form and 
internal nature of man and beast. The sooner the operation is per- 
formed after birth, the more certain are its effects. Were a natu- 
ralist from a unisexual world to visit this earth of ours it would be 
difficult to convince him that a brother and a sister were of the same 
species, or that the wrinkled, sallow-visaged eunuch with his beard- 
less face, his long, tapering limbs, his hesitating carriage, his carping 
outlook, and corpulent body was brother to the thick-set, robust, 
pugilistic man with the bearded face. The discovery that the testicle 
and ovary contain, scattered throughout their substance, a small 
glandidar element which has nothing to do v\ ith their main func- 
tion — the production of genital cells— was made 70 years ago, but 
the evidence which leads us to believe that this scattered element — 
the interstitial gland — is directly concerned in the mechanism of 
growth is of quite recent date. All those changes which we may ob- 
serve in the girl or boy at puberty — the phase of growth which brings 
into full prominence their racial characteristics — depend on the ac- 
tion of the interstitial glands. If they are removed or remain in 
abeyance the maturation of the body is both prolonged and altered. 
In seeking for the mechanism which shapes mankind into races we 
must take the interstitial gland into our reckoning. I am of opinion 
that the sexual differentiation — the robust manifestations of the male 
characters — is more emphatic in the Caucasian than in either the 
Mongol or Negro racial types. In both Mongol and Negro, in their 
most representative form, we find a beardless face and almost hairless 
body, and in certain NegTO types, especially in Nilotic tribes, with 
their long, storklike legs, we seem to have a manifestation of abey- 
ance in the action of the interstitial glands. At the close of sexual 
life we often see the features of a woman assume a coarser and more 
masculine appearance. 
