It is a familiar observation that high altitudes, with their lowered barometric pressures, may interfere with the physiologic functions of perfectly healthy persons who encounter such environmental conditions for the first time. The untoward effects are ascribed primarily to the lack of oxygen resulting from the lowered partial pressure of the indispensable respiratory gas. Other factors, such as fatigue, may add to the discomforts that are familiar as mountain sickness and aviators' disease; but the foremost symptoms are clearly referable to some degree of oxygen want. To some persons the characteristic malaise comes at heights of only a few thousand feet above sea level; others are not affected until the barometer becomes notably low. In any event physiologic adjustments seem to occur within a short period, whereupon the affected persons are said to be acclimatized.
In 1878, Paul Bert1 predicted that the blood of man and animals living at