Blood pH in Vivo. I. Changes Due to Respiration *

The sensitivity of the cortex to variations of its pH within the physiological range is striking.' It is highly probable that the activity of other organs is similarly affected by their acidity. The intimate relation of the blood and its capacity to condition these reacting systems is obvious. However, very little is known of the actual moment-to-moment fluctuations of the hydrogen concentration of the blood in living animals. It is important, therefore, that further knowledge of changes in blood acidity under various conditions be obtained, including not only the magnitude of the alterations, but also the speed at which they occur. The present paper reports observations on the pH of arterial blood under various conditions of respiration. Method