Each with the signs peculiar to it can be identified among the faces that pass one in the street.  And they differ so markedly among themselves that they provide a new and accurate means of classifying varieties among the races of the species:  man.  The thyroid type differs as much from the adrenal type as does a greyhound from a bull-dog.  The greyhound has a certain size, form, character and capacity.  The bull-dog has similar qualities which are yet quite different.  Each is built for a particular career.  Among human beings, the pure thyroid type is easily distinguished from the pure adrenal type, and both of these from the pure pituitary type.  Each is stamped with a significant figure, height, skin, hair, temperament, ambition, social reactions and predisposition to certain diseases.

THE MIXED TYPES

Among the mixed types, the lines of distinction are less clear, and so they are more difficult to classify.  The mixed types may be said to be hyphenated.  In them, two or even three of the internal secretory glands conflict for predominance.  The combined action makes for a resultant modification in the primary glandular markings and effects.  A hyphenated classification thus becomes inevitable.  Especially is this so if the two glands are mutually antagonistic and inhibitory.  A compromise effect is then necessitated.  Or an individual may be dominated by one gland at one period of his life and by another at a later period.  One of the glands, the thyroid, for example, will show, by the traces it has left upon the earliest developing features, that it was in control at the very earliest dates of his history, while other signs will disclose the more recent influence of the adrenal or of the pituitary.  The combination becomes classifiable as the thyroid-pituitary type, or as the thyroid-adrenal type.

That the external features as well as the chronic diseases of human beings are controlled by some common factor has long been suspected.  Inquiries into morbid phenomena with a hereditary trend yielded information that has paved the way for the internal secretion theory.  It has long been known that certain diseases effect only certain individuals of a definite constitution.  Apoplexy, diabetes, arteriosclerosis, Bright’s disease, are met with almost exclusively in what the older clinicians talked about as the apopleptic type.  On the other hand, they said, anemias, tuberculosis, hemophilias, scrofulas occurred more among the lymphatic type.  But they had no idea whatever of the true functional basis of the two different types.  The truth as we of today view it is that these two types represent different textures of human beings, fabricated of different internal secretions.  They are really two different breeds of the species Homo Sapiens.  The materials being different, the color and feel of them is different, and the resistance to wear and tear is different.