Metabolism of steroids: 4. Ketonic acids derived from cholic acid.

acid also increases on storage it is not-yet possible to say in which form the vitamin is primarily synthesized. The nature of the changes underlying the phenomenon is still obscure. The evidence strongly suggests, but does not absolutely prove, that the vitamin is formed from a chemically related precuesor during storage. The increase of vitamin C in an apple of about 22 g. during 7 months of storage was found to be equivalent to about 2 mg. of ascorbic acid, the total content reaching a level of about 7 mg. per fruit. Some years the increase is somewhat greater (cf. Fig. 1). On the other hand, the total vitamin content per apple picked normally in October of the same year was about 24 mg..The ' otal quantity of the vitamin present in these immature fruits was therefore very much less than that foumd in a Bramley's Seedling apple, picked at the usual time. If it be assumed that the precursor in young apples is fully utilized during storage, the extra vitamin found in the apple matured on the tree must in consequence have either been synthesized in the fruit from a precursor supplied from other parts of the plant as the apple developed or, more probably, it must have reached the fruit in a preformed state. Even if the latter were the case, the process of formation of the vitamin may be similar to that occurring during the storage of the young apple. These and other points which arise cannot be settled on the basis of existing knowledge and the information so far obtained is insufficient to shape a comprehensive hypothesis. Nevertheless the data presented here are consistent enough to serve as a basis for a rpore detailed inquiry, the results of which might eventually throw some light on the physiological function of I-ascorbic acid not only in the plant but also indirectly in the animal organism.