It is after puberty, when the thymus should shrink and pass out of the endocrine concert as a power, that the more complex reactions of personality emerge when the thymus persists and refuses to or cannot retire.  The persistent thymus always then throws its shadow over the entire personality.  To what extent that shadow spreads depends upon the strength of the other glands of internal secretion, their ability to compensate or to stay inhibited.  Whether or not the pituitary will be able to enlarge in its bony cradle seems to be the most important factor determining these variations.  If there is space for it to grow, at any rate normally, the individual may pass for normal, although he will have difficulties throughout life he may never understand, particularly in sexual directions.  If the pituitary is limited. partially or completely, the thymus predominance is more prominent and fixed, and the abnormalities become obvious, both of person and conduct.

The anatomic architecture of the latter thymo-centric personality is fairly typical.  The reversion in type of the reproductive organs, the slender waist, the gracefully formed body, the rounded limbs, the long chest and the feminine pelvis strike one at the first glance.  The texture of the skin is smooth as a baby’s, and sometimes velvety to the touch.  Its color may be an opaque white, or faintly creamy, or there may be an effect of a filmy sheen over a florid complexion.  Little or no hair on the face contributes to the general feminine aspect in the more extreme types.  They are often double jointed somewhere, flat footed, knock-kneed.

In women, the external manifestations of a thymo-centric personality may be limited to thinness and delicacy of the skin, narrow waist, rather poorly developed breasts, arched thighs and scanty hair, with scanty and delayed menstruation.  Or there may be obesity, with juvenility, if there is a repression of the pituitary secretion for one reason or other.

In their reactions to the problems, physical and psychic, of everyday life, the thymo-centrics are distinctly at a disadvantage.  In the first place, muscular strain, stress or shock is dangerous to them because they have a small heart, and remarkably fragile blood vessels, which renders their circulation incapable of responding to an emergency, or at least definitely handicapped.  In infancy, they may die suddenly because of this, either for no ascertainable cause at all, or because of some slight excitement like that attending some slight operation, a fall, or a mild illness.  During the run-about epoch they are unable to cope with the necessities of an active child’s existence in playing with other children.  Puberty and adolescence are specially perilous to them for they may endeavour to compensate for an inner feeling of physical inferiority by going in strenuously for athletics and sports, and so risking a sudden hemorrhage in the brain, producible by the tearing of a blood vessel, as if constructed of defective rubber.  Reports published in the newspapers from time to time of children or young men instantly killed by a tap on the jaw in a boxing contest, or some other trivial injuries are doubtless samples of such reactions in thymo-centric people.