Acidity inhibits the functions of the cerebral cortex, but stimulates those of the medulla. This antithetic reaction to the stimulus of increased H-ion concentration is an adaptation to prevent animals from committing suicide by over-activity, for the mechanism for the initiation and control of the transformation of energy is in the higher centers of the brain, while an essential part of the mechanism for the neutralization of acidity--the centers governing circulation and respiration-- is in the medulla. This explains many clinical phenomena-- why excessive acidity causes paralysis, why there is great thirst after inhalation anesthesia, after excessive muscular activity, excessive emotion--after all those activities which we have found to be acid-producing, for water, like air, neutralizes acids. The excessive use of alcohol, anesthetics, excessive work, intense emotion, all produce lesions of the kidney and of the liver. The explanation is found in the fact that all these stimuli increase the acidity of the blood. and that, if long continued, the neutralizing mechanism must be broken down and so the end-products of metabolism are insufficiently prepared for elimination. In view of these considerations we may well conclude that the maintenance of the normal potential alkalinity of the blood is to be estimated as the keystone of the foundation of life itself. INDEX ABDOMEN, diseases of, phylogenetic association and, 44 Acidity, 227 Adaptive energy, 176 variation in rate of energy discharge, 177 Adrenalin, Cannon's test for, 134, 196 injection of, changes in brain-cells from, 186 Adrenals, 196 brain and, relation of, 1.98 diseases of, effect of, on output of energy, 216 functional study of, 196 histologic study of, 198 Alcohol, changes in brain-cells from, 116 Alkalescence, 227 Anemia, pain of, 77 Anesthesia, 2, 227 anoci-association and, differentiation, 34 effect of trauma under, upon brain that remains awake, 3 inhalation, cause of exhaustion of brain-cells as result of trauma under, 8 theory of, 227 Anger, 63, 70 Anoci-association, 34 anesthesia and, differentiation, 34 Graves' disease and, 36 prevention of shock by application of principle of, 36 Aristotle, 127 Asher, :37 Associational centers, dulled, 47 Austin, 2, 55, 173