1. The system:hemolyzed blood + glucose never exhibits glycolysis or, in the air, oxidation of glucose. When glucose is replaced by hexosephosphate ester, addition of methylene blue causes oxidation in air. 2. When cozymase is added also, the oxidation is increased, and a synthesis of hexosephosphate esters takes place. 3. When pyocyanine is used instead of methylene blue, the rate of oxidation is the same as with methylene blue, but a synthesis of phosphate esters takes place without addition of cozymase. 4. There is never a phosphate ester synthesis without oxidation going on, but oxidation does not necessarily go hand in hand with phosphate synthesis. 5. In order to couple the oxidation process with phosphate synthesis, two methods are available: either to start oxidation by methylene blue and to add coenzyme from yeast cells; or to start oxidation by pyocyanine, in which case coenzyme is unnecessary, though it improves the effect. 6. Iodoacetate always suppresses synthesis, but only under certain conditions decreases oxidation. Cyanide has no effect upon either process.