exhibitionism.  On the other hand, in states of thyroid insufficiency, depression is produced, which may go on to melancholia, a desire to be alone, to hide, to sit apart and even a tendency to accuse the self of various uncommitted crimes and sins.  In the form of cyclic insanity known as the manic-depressive psychosis, mania alternates with depression, as if the personality were dominated wholly in turn by one or the other of these two instincts of the ego.  There is a good deal of evidence that behind them is a corresponding fluctuation in the amount the thyroid secretes into the blood.  Among the thyroid-centered attitudes toward the self gyrate more than in any other type.  Egomania and megalomania occur most often in thyroid unstable individuals.

ENERGY AND SENSITIVITY

In his classic Inquiries into Human Faculty, Francis Galton laid down some fundamental considerations concerning energy and sensitivity as mental traits.  Energy he defined as the capacity for labor, and declared it to be the measure of the fullness of life or vitality.  Statistical study by him of men of genius and their ancestors showed them to be endowed with a large amount of energy.  It has been said to be the absolute prerequisite of genius.  Now if there is a single fact that has been well established by investigations of the internal secretions, it is that the energy quantum of an individual is a function of and determined by his thyroid.  The more thyroid he has, the more energetic will he be—­the less thyroid the less energetic, and the lazier.  The thyroid-centered individual, of the excess thyroid type, actually burns up more food and produces more heat than the ordinary organism.  He burns himself up faster in general.

When the thyroid sends more secretion into the blood, more thyroxin, it accelerates all the functions and activities of the organs.  Tea and coffee produce loquacity because they stimulate the thyroid.  People with thyroid dominant constitutions talk fluently, rapidly, and continuously.  Their energy makes them doers, actors rather than spectators.  They get up early in the morning, are on the go all day without surcease or fatigue, go to bed late, and often suffer from insomnia.

Thyroid deficients, however, are definitely the opposite.  They are quite conscious of the limited reserve of energy at their command.  Also that they need plenty of refreshing sleep.  Early to bed and late to rise remains the leading maxim of health for them.  In addition they find it necessary to sleep during the day.  Forty winks or more in the afternoon makes a good deal of difference to them.  Taciturn, inarticulate, lazy, slow, tired, are the adjectives applied to them by their friends as well as by their enemies.  All because of an insufficient or inefficient supply of the thyroid’s iodine to their cells.  The mobility of energy in an organism is a measure of the amount of active iodine in it.  The physiologic synonyms for “energetic and lazy” are “well-iodinized” and “poorly iodinized.”