Ii. Physiologic Observations and Methods

The resistance and compensatory power of the nor- mal man against low oxygen have been found to be practically the same qualities as "condition" or "train- ing" in the athlete; and lack of compensatory power equivalent to being "out of training."In its more extreme forms it is identical with a "weak heart."From this it follows in theory, as the cardiovascular division in the Research Laboratory has in fact dis- covered, that the methods based on the rebreathing apparatus are not only applicable for measuring "fit- ness" and "staleness" in the aviator, but also offer hope for development into that long sought and greatly needed aid to cardiovascular diagnosis : a general test and measure of the "functional power of the heart."It will be evident, however, that by the expression "functional power of the heart" we mean much more than merely the strength of that organ.We mean, rather, the totality of the processes of the body's gaseous exchanges with its atmospheric environment.