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.