EAGIAL TYPES KEITH. 449 
The skin as a whole looks transparent ; the hair of the scalp becomes 
scanty ; the pubic and axillary hair, with the eyelashes and eyebrows, 
often falls out; in many cases the teeth are brittle and carious. All 
these appearances disappear under the administration of thyroid 
extract." We have here conclusive evidence that the thyroid acts 
directly on the skin and hair, just the structures we employ in the 
classification of human races. The influence of the thja'oid on the 
development of the other systems of the body, particularly on the 
g^rowth of the slmll and skeleton, is equally profound. This is par- 
ticularly the case as regards the base of the skull and the nose. The 
arrest of growth falls mainly on the basal part of the skull, with the 
result that the root of the nose appears to be flattened and drawn 
backwards between the ej^es, the upper forehead appears projecting 
or bulging, the face appears flattened, and the bony scafTolding of 
the nose, particularly when compared with the prominence of the 
jaws, is greatly reduced. Now, these facial features which I have 
enumerated give the Mongolian face its characteristic aspect, and, to 
a lesser degree, they are also to be traced in the features of the Negro. 
Indeed, in one aberrant branch of the Negro race — the Bushman of 
South Africa — the thyroid facies is even more emphatically brought 
out than in the most typical Mongol. You will observe that, in my 
opinion, the thyroid — or a reduction or alteration in the activity of 
the thyroid — has been a factor in determining some of the racial 
characteristics of the Mongol and the Negro races. I know of a 
telling piece of evidence which supports this thesis. Some years ago 
there died in the East End of London a Chinese giant — the subject, 
we must suppose, of an excessive action of the pituitary gland — the 
gland which I regard as playing a predominant part in shaping the 
face and bodily form of the European. The skeleton of this giant 
was prepared and placed in the museum of the London Hospital 
Medical College by Col. T. H. Openshaw, and anyone inspecting that 
skeleton can see that, although certain Chinese features are still 
recognizable, the nasal region and the supra-orbital ridges of the face 
have assumed the more prominent European type. 
There are two peculiar and yerj definite forms of dwarfism with 
which most people are familiar, both of which must be regarded as 
due to a defect in the growth-regulating mechanism of the thyroid. 
Now, one of these forms of dwarfism is known to medical men as 
achondroplasia, because the growth of cartilage is particularly af- 
fected, but in familiar language we may speak of the sufferers from 
this disorder of growth as being of the " bulldog breed " or of the 
" dachshund breed." In the dachshund the limbs are greatly short- 
ened and gnarled, but the nose or snout suffers no reduction, while 
in the bulldog the nose and nasal part of the face are greatly reduced 
and withdrawn, showing an exaggerated degree of Mongolism. 
