4. Specific types of personality may be directly associated with particular glandular prominences, so that we have the thyroid-centered types, the pituitary-centered types, the adrenal-centered types, etc. These are the classic Three, the prototypes in their purity most easily described and recognized. 5. Combinations of these, as well as of other glands--with joint predominance--occur and indeed form the majority of populations. The phenomena of varieties in species are thus explained. 6. Internal secretion traits are inherited, and variations in heredity are essentially the structural representation of the resultant of a parallelogram of forces exerted by each of the parental prepotent glands. If they are of the same type, they may reinforce each other: if not, inhibitions and compensations will come into play. Mendelian laws may apply. 7. The process of evolution, as the play of natural selection upon these variations, becomes comprehensible from a new standpoint. 8. Certain diseases, and disease tendencies, both acute and constitutional, as well as traits of temperament and character, and predetermined reactions to certain recurring situations in life, are rooted in the glandular soils that compose the stuff of the individual. 9. The subconscious, of which the vegetative apparatus is the physical basis, leads back to the internal secretions for the profoundest springs of its secrets. We shall see how and why. 10. Given the internal secretory composition, so to speak, of an individual--his endocrine formula--and so his intravisceral pressures, one may predict, within limits, his physical and psychic make-up, the general lines of his life, diseases, tastes, idiosyncrasies and habits. 11. Within limits, if the previous history of an individual is known, his physical appearance may be approximately described, and his future outlined. 12. Conversely, given the physical and psychic composition of an individual, and his past history, one may deduce the internal secretion type to which he belongs. Examples: A. One Thyroid-centered Type has Bright eyes Good clean teeth Symmetrical features Moist flushed skin Temperamental attitude toward life Tendency to heart, intestinal and nervous disease B. One Pituitary-centered Type Abnormally large or small size Musical--acute sense of rhythm Asymmetrical features Tendency to cyclic or periodic diseases C. One Adrenal-centered Type Hairy Dark Masculinity marked Tendency to diphtheria and hernia These are some of the master types. They have their variants depending upon the influences of the other glands, especially the interstitial cells of the sex glands. ANTE-NATAL DEVELOPMENT