Abstract
A diminution in the carbon dioxide content of the blood is a constant feature in pneumonia. Occasional cases, however, may fail to show low carbon dioxide. The carbon dioxide in the blood bears little definite relation to the severity of the disease, except that it tends to be lowest in severe cases and in the terminal stages of the disease. There is less deviation from the normal in short or mild cases. The diminution in the carbon dioxide in the blood bears no immediate relation to temperature, as it may persist for some days after the patient is afebrile. The diminution in carbon dioxide corresponds to the other evidences of metabolic changes in infection and, like them, may be even greater after than during the febrile period. The changes in the carbon dioxide content of the blood run parallel to the output of ammonia in the urine. The carbon dioxide appears to bear no relation to chlorine excretion. In two unusual cases the carbon dioxide content of the blood was normal or above normal. This was associated with a very low oxygen content of the venous blood.