Studies in the Acetone Concentration in Blood, Urine, and Alveolar Air. III: The Elimination of Acetone through the Lungs.

IN the following an attempt is made at an exact analysis of the passage of acetone into the expiratory air, and in so doing I have tried in the main to follow the method of analysis adopted in modern experiments in regard to the exchange of respiratory gases'. If the passage of acetone into the alveolar air is a pure diffusion process, the partial pressure of the acetone vapour in the latter should never be higher than the partial pressure in the blood. But if, on the contrary, an energetic, secretory activity is contributed by the lungs, the partial pressure of the acetone in the alveolar air may be higher than in the blood. The decision of these points becomes much more simple in the case of acetone than in the case of the respiratory gases. The latter are partly dissolved and partly in chemical combination in the blood, and their concentrations are subjected to great variations in the venous and the arterial blood. The acetone, on the other hand, is exclusively dissolved in the blood, and the concentration remains pretty nearly constant for hours [Widmark, 1919]. Certainly after resorption no demonstrable difference in concentration occurs in the arterial and venous blood. In the physiology of respiration the absorption coefficient, as defined by Bunsen [1877], has been used in the estimation of the pressure of the gases in blood and air. The custom of thus expressing by the absorption coefficient the partition of a gas between a fluid and a gas above the fluid is associated with the fact that the gas analyses have chiefly been carried out by the eudiometric method. The absorption coefficient may evidently be regarded as a partition coefficient for the gas in question with reference to a fluid and a gaseous phase, respect being taken to the particular pressure and temperature of the gases. If we estimate in the direct chemical way the concentration of a substance which is divided between a gaseous and a fluid medium it is to a certain