The internal secretions influence the amount and duration of the memory deposits. The thyroid appears to be essential to the _laying down_ of the memory trace. Cretins have poor memories on the retention side and so cannot learn. The memory of thyroid insufficients is wretched. In the extreme grades, the memory for recent occurrences becomes completely lost. Iodine and thyroid increase the electric conductivity of the brain, so that the memory trace must be deposited more easily in those who have an excess of thyroid. Removal of the thyroid produces a degeneration of nerve cells and their processes, and associative memory becomes difficult or impossible because conduction from cell to cell is interfered with. If sufficient thyroid is fed in excess, brain conduction may be so facilitated that epilepsy may result upon slight irritation. On the other hand, the pituitary seems to be related to _preservation_ of the memory deposit. In conditions of disease of the pituitary, loss of memory for past experiences is more marked. As regards recent experiences, they are better held, although in a sort of subconscious manner, recoverable when the condition improves or is cured. But the greatest difference between the thyroid and pituitary effects upon memory exists as regards material: the thyroid memory applies particularly to perception and percepts, the pituitary to conception (reading, studying, thinking) and concepts. Judgment is another mental process that often intervenes between sensation and the energy-reaction. It involves memory and association of experiences. Behind it is an attitude as much as there is in an emotion or the arousing of an instinct. Beliefs and reasonings are complex judgments. They form the units of the intellectual process. There is an element of speed in judgment on reasoning as in perception and memory. And as in the latter, the thyroid determines the velocity. Quick thinking, as we call it, means good thyroid action, and slow thinking deficient thyroid action. The other element in judgment, accuracy, is influenced by the ante-pituitary. During adolescence there is physical growth which consumes most of the secretion of the ante-pituitary. After adolescence, after the early twenties, when physical growth has ceased, the ante-pituitary secretion sensitizes the cells of the brain to mental growth. The reaction potential of the ante-pituitary, that is its inherent, latent ability to supply a maximum of its endocrine for the nerve cells of the frontal lobes, is the best-known chemical determinant of intellectual genius. It makes for the greatest co-ordination of experience, knowledge, information, tastes and problems into one harmonious whole. And curiously, not only does it cause a fusion of intellectual material: it creates a desire for and a love of such material.