The volume of the “dead space” in breathing

IN a recent paper Douglas and Haldane' have published a series of experiments to show that the " dead space" may be increased during muscular work to several times the resting volume. They observed a very regular increase from 160 c.c. during rest in bed to 622 c.c. while the subject walked at the rate of five miles an hour, with a corresponding increase in metabolism from 237 c.c. to 2573 c.c. oxygen per minute. When this paper appeared we were preparing for publication a series of experiments on the regulation of respiration and circutlation during the initial stages of muscular work. We had assumed a constant dead space, and if Douglas and Haldane were right we would have to recalculate all oiur experiments and reconsider several portions of our argument. We could not, for reasons to be stated presently, accept the results of Douglas and Haldane as binding, but on the other hand we could not disregard them, as they might very well be correct-at least qualitatively-and it became necessary therefore that we should attempt also a determination of the dead space under the conditions of rest and work. Douglas and Haldane have calculated the dead space from (1) the CO2 percentage of the expired air, (2) the average CO2 percentage of the alveolar air and (3) the average volume of one breath. The average volume of one breath and the CO2 percentage of the expired air were determined from respiration experiments made by means of the Douglas respiration apparatus, and we have no doubt that the accuracy was ample for the purpose. The average composition of the alveolar air was determined by the method of Haldane and Priestleyl as the average of samples taken by a sharp expiration at the end of a normal inspiration and at the end of a normal expiration. This method will give fairly consistent results, and when the mean is taken of a number of determinations the accidental error may become very small, but there