The dependence on air of all mankind, and indeed all known terrestrial animals, was recognized by primitive tribesmen long before any of them were distinguished from their fellows by being called healers. No matter the technological sophistication of ultramodern molecular research, and no matter the increasingly abstruse terminology of its current literature, the circle of knowledge always returns to its starting point: In order to live, man must have air. In the late eighteenth century, it was found that not air in general but one particular component of it, oxygen, is the crucial factor on which life depends. The conception of man as an obligate aerobe then took on a more specific meaning: We have no choice—without oxygen, our cells die and we die with them. Oxygen absorption was soon thereafter shown to be the reason that the color of blood turns instantly from a dark tiredness to the bright red of vibrant life as it passes through the lungs; its departure into the cells of the body’s distant tissues was recognized as the cause of blood’s exhaustion when it returns depleted and blue from the long journey, figuratively gasping for air.
