The question of the controlling factors in the regulation of respiration has furnished one of the long-debated topics of physiology. Excess of carbon dioxid and deficiency of oxygen in the circulation have each been credited with being the effective agent in promoting increased respiration. The trend of recent investigation has tended to show that each of these may represent a factor of moment, inasmuch as the respiratory center can be excited by either condition; but it has now been established, in particular by the studies of Haldane and his pupils in England, that the sensitivity of the center to carbon dioxid is by far the more important feature of the increased respiratory movements in asphyxia. Indeed, it is the only chemical factor which can at present be regarded as playing any important part in the regulation of the respiratory movements under normal conditions.
The acquisition of a fundamental chemical basis