When some twenty-five years ago I began making notes of the effects of altitude on the human animal, I never dreamt I should be called upon to make public any of my observations; I am doing so now with the utmost diffidence and buoyed up by the hope that a few of the facts I am about to bring to your notice may be even indirectly useful.

In view of the rapidly approaching use of commercial aviation as a means of passenger transport, I wish it to be clearly understood that I am not approaching the subject from the purely scientific point of view, but rather from the standpoint of the men in the street, whose experience of altitude may be very moderate, as indeed is my own.