The Regulation of Respiration Iii. a Continuous Method of Recording Changes in Acidity Applied to the Circulating Blood and Other Body Fluids’

The importance of a constant hydrogen ion concentration of the arterial blood to normal tissue function has been greatly stressed within the past decade. The apparent dependency of tissue acidity on blood acidity coupled with the constancy of the arterial hydrogen ion concentration in the normal individual seemed to justify this emphasis. This constancy of hydrogen ion concentration of the arterial blood was attributed to the ‘extreme sensitivity of the respiratory center to the free,hydrogen ion of the blood. In fact this view became so firmly established that the absence of a demonstrable increased acidity of the arterial blood during hyperpnea was considered indicative of the supersensitivity of the respiratory center to the present physico-chemical methods of detecting the hydrogen ion. It is, therefore, not surprising that the technique for the determination of the hydrogen ion concentration of the blood has advanced so rapidly within the past few years. It seems now, however, that the problem of respiratory control must be considered from a somewhat different angle. Direct experiments (1) and the review of extensive literature (2) indicate a gross insensitivity of the respiratory mechanism to the free hydrogen ion of the arterial blood. Indeed, the relatively greater frequency of the inverse relation of pulmonary ventilation to the hydrogen ion concentration of the blood indicates that a causal relationship is wanting. Hence a detailed elucidation of the relation of pulmonary ventilation to the hydrogen ion concentration of the blood seemed of sufficient interest to warrant an effort to develop a continuous method of recording changes in the hydrogen ion concentration of the circulating blood. The advantages of a continuous method in determining the time relation of acidity changes to