THE INTERNAL ENVIRONMENT AND BEHAVIOR : Part IV. Carbon Dioxide and Acid-Base Balance.

Considering the experimental results obtained it is evident that all too often we must rely on rather casual observations, and that the number of experiments planned to determine relationship between behavior and shifts in acid-base equilibrium is relatively few. However, from the literature we can see that extensive dis-placement in any direction from the normal area will result in impaired mental function and loss of consciousness, although few quantitative measurements of mental functions or behavior are available. However, certain facilitative reactions may be discovered when acid-base equilibrium is displaced within physiological limits. Slight increases in pH and decrease in CO₂ tension tend to increase motor reactivity to stimuli, particularly at the reflex level, but to decrease functions involving higher levels of the central nervous system. On the other hand, a slight decrease in pH or increase in CO₂ tension may have a facilitative response to a small extent. It is possible that these effects may be due to vaso-motor changes in the cerebral cortex, although proof is still lacking.

No data on the effects of changes in bicarbonate content of blood on behavior are available. With the exception of the experiments on cerebral stimulation in schizophrenia from high CO₂ tension, all the results tend to indicate impairment of function rather than facilitation when the acid-base equilibrium is displaced. The consideration of the possible mechanisms of action indicate the complexity and interrelationship between a variety of variables ranging from ionic strength to shifts in water. In order to obtain a conception of the effects of alterations in acid-base equilibrium on behavior it is obvious that many experiments will need to be performed in which the wide range of variables are measured simultaneously. Even though it may be impossible to control each factor independently by experimental technique, it may be possible to submit the observational data to analysis by other methods.