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1. A survey of the literature onLicania rigida has been made and the more important chemical contributions briefly reviewed. Attempt has been made to include a complete bibliography with this paper. 2. It appears from the experimental evidence obtained in this work that licanic acid possesses no apparent energy value and that under the conditions described is slightly deleterious to the growth of young rats. 3. Licanic acid has some efficiency in the animal. It is capable, in the rat, of assisting in the utilization of lactose in milk as indicated by its prophylactic action in preventing sugar loss via the urine.

DURING the last decade, distinct advances have been made in our knowledge of the chemistry and physiology of vitamins. Perhaps some of the most interesting observations have been made in the field of the vitamin B complex. There may be two reasons for this situation. First, the chemical structure of the water-soluble vitamins is somewhat less complicated than that of the fat-soluble vitamins. Vitamin B1 was first synthesized in 1936, and we have seen an average of one B vitamin synthesized a year since that time. Secondly, at least three of the B vitamins have found their physiological function as prosthetic groups of enzymes in very important enzyme systems. The work on the relation of these vitamins to metabolism has not only aided us in understanding the function of the vitamins, but in many cases it has also helped us to understand the intricacies of metabolism itself.

IT has been demonstrated that a riboflavin deficiency in the rat produces a marked derangement in those enzyme systems which are involved in the oxidation of certain intermediates of carbohydrate metabolism (Axelrod and Elvehjem, unpublished results). The possible effects of such a deficiency upon the metabolism of amino-acids have been suggested by the discovery of Warburg and Christian1that the prosthetic group of the d-amino-acid oxidase of Krebs2 is a flavin-adenine dinucleotide.

DURING the past two years, we have been working on the isolation of vitamin B2, using the chick for assay work. Only those fractions which had the power of preventing pellagra and allowing normal growth in chicks on the vitamin B2 low ration described by Kline, Keenan, Elvehjem and Hart1 were considered to be potent in vitamin B2. All our results point to the fact that vitamin B2 and flavine are not identical.

IT is now well recognized, largely through the efforts of the Euler and Warburg laboratories, that nicotinic acid amide is a constituent of both coenzyme I and coenzyme II. Since these coenzymes have such an important role in the metabolic processes of the body, it is of decided importance to acquire more information concerning their physiology. A good deal has been learned from studies with synthetic enzyme systems in which these coenzymes are involved. The in vivo approach has been attempted by the Euler group. They have confined themselves to rats as the experimental animals and have encountered many obstacles in their work, since it has been very difficult to demonstrate a clear-cut deficiency in the rat of the coenzymes or of any of their possible precursors. Recently, however, Elvehjem and co-workers1 have demonstrated a definite nicotinic acid deficiency in the dog, and Dr. H. Chick et al.2 have made similar observations on the pig. We have thus been enabled to work with two different species in which a definite nicotinic acid deficiency is relatively easy to produce.

WE have previously demonstrated that thiamin pyrophosphate may be synthesized from the free vitamin by the action of enzymes present in alkaline washed brewer's bottom yeast, provided that hexose-diphosphate and certain factors present in boiled aqueous extracts of animal tissues are present1,3. Synthesis under these conditions was completely inhibited by 0·005 M. sodium iodoacetate, but was relatively unaffected by 0·04 M. sodium fluoride. More recently3, we have demonstrated that cozymase and acetaldehyde may be substituted for the boiled tissue extract with no change in the degree of synthesis or of the iodoacetate inhibition. Phosphoglyceric acid may also be substituted for the boiled tissue extract, but under these conditions iodoacetate fails to affect the synthesis while fluoride causes complete inhibition3. Using specially prepared alkaline washed yeast, we have found that cocarboxylase synthesis with phosphoglyceric acid is considerably diminished. It may be restored, however, by the addition of catalytic quantities of adenylic acid. As a result of these experiments we have proposed the reaction

THE successful study of vitamins depends to a large extent upon the production of uncomplicated symptoms in experimental animals which can be cured by purified preparations of the vitamin in question. However, the cure of certain symptoms even with crystalline preparations does not necessarily mean that the deficiency was due to a lack of the factor fed. We have recently encountered such conditions in our laboratory and wish to describe one such relationship briefly.