The Regulation of Respiration Iv. Tissue Acidity, Blood Acidity and Pulmonary Ventilation. a Study of the Effects of Semipermeability of Membranes and the Buffering Action of Tissues with the Continuous Method of Recording Changes in Acidity~

Several years ago experiments by one of us pointed to a lack of correspondence between blood acidity and pulmonary ventilation, which seemed to contradict the generally accepted view that the acidity of the arterial blood controlled respiration. These experiments (1) led to the statement that “The conception that the hydrogen ion concentration of the arterial blood regulates respiration is analyzed and found wanting;” that “Parallelism between pulmonary ventilation and arterial pH is an accidental occurrence prevailing only under special conditions.” Considering respiratory control as a problem in transportation-the blood carrying acid to and from the cells and the metabolism of the cells determining the kind and amount of acid leaving and entering the cellsthere was no reason for assuming a constant relation between blood and tissue acidity. It was pointed out that the more acid arterial blood may be the more efficient in carrying acid away from the tissues, that blood acidity can at best be only an indirect criterion of tissue acidity, that blood acidity and tissue acidity may vary in opposite directions as well as in the same direction. An effort to correlate the net effect of innumerable factors involved in changes of blood and tissue acidity under a variety of conditions pointed to a high coincidence of a direct relation of pulmonary ventilation to the acidity of the respiratory center itself. This led to the advancement of a working hypothesis connecting tissue acidity rather than blood acidity with the behavior of the respiratory center. AS to the lack of correspondence between pulmonary ventilation and blood acidity-that must be accepted as a fact. The graphic record of changes in acidity of the circulating blood leaves no room for doubt (2)