Vol. 38 ACTION OF PANTOYLTAURINE AND PANTOTHENATE

fluid, and Tables 3 and 6 that the glycolysis of suspensions is unaffected by the compound. A small stimulation only was fotmd in previous experiments with the same organism (McIlwain, 1944) in which, in contrast with the present work, the course of glycolysis was measured. Pantothenate is always present in small quantities in the organisms; nevertheless, if free pantothenate is present, it is metabolized. As the association of the usage of added pantothenate with glycolysis is facultative, it is understandable that pantoyltaurine should be able, as is found, to depress pantothenate-usage without much effect upon glycolysis. The organism in presence of pantothenate and pantoyltaurine is then reverting to a condition similar to that obtaining when neither is present. This condition may be adequate for glycolysis but is not adequate for growth. The association of pantothenate-usage with growth Is obligatory: growth is strictly limited by the quantity of pantothenate added when that is below a given concentration (McIlwain, 1944), and the limiting quantities are completely removed from the media. Pantoyltaurine in such cases prevents both the pantothenate metabolism and growth. (5) To explain inhibition of growth by a process which preserves the growth-essential, pantothenate, it can be supposed that, in its functioning, pantothenate undergoes a cycle of changes, which is inter-* rupted by pantoyltaurine, and of which at least one phase is relatively unstable in the presence of the reaction mixture. SUMMARY