In the pure types, only one gland, either by being present in great excess above the average, or by being pretty well below the average, comes to exercise the dominating influence upon the traits of the organism. As the strongest link in the chain, or as the weakest, it rules. The others must accommodate themselves to it. Among them as commanders of growth, development and normal function, it holds the balance of power. In every emergency it stands out by its strength or by its weakness. It thus creates its own type of man or woman, with attributes and characteristics peculiar to itself. These pure types, as we have seen, are mainly the thyroid, the pituitary, and the adrenal-centered. 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.