The history of civilization is replete with the records of human success in the most varied sorts of encounters against the forces of nature. Fire, wind and water have not only been subdued by man but also have been put to use in manifold ways that suit his purposes. His resourcefulness in the conquest of natural agencies and in the subjugation of other living creatures has become so largely a part of our everyday life that we cease to appreciate its real marvels. There are, however, further conflicts with nature that call for something more than mere technical ingenuity or mechanical power. Nothing short of the application of scientific knowledge has sufficed to enable man to submerge himself in the depths of the ocean or penetrate the upper reaches of the atmosphere. Physics and chemistry have been compelled to call physiology to their aid in such undertakings.
Whenever the human