If one may think of carbon as the basic element of organic structure, one may similarly look on oxygen as the basis of organic function. A considerable portion of the machinery of Metazoa is devoted to delivering an adequate supply of oxygen at the door of the individual cell, and the presence of special mechanisms (such as the carotid body) to insure the supply to the brain, as well as the prompt disturbance of neural function when oxygen is lacking, attests the special importance of oxygen for this organ. Neurons, like other body cells, require a continuous supply of energy for maintenance and action. This is obtained, in orthodox fashion, by oxidations with molecular oxygen in cell respiration and, to a lesser extent, by oxidations with organic molecules in the dismutations of glycolysis. Respiration of brain differs from that of muscle, so extensively studied as to be the tissue of