=The Mode of Action of the Vitamine.=--One of the most interesting as well as puzzling questions in regard to the antiscorbutic vitamine concerns the manner in which it prevents or cures scurvy. It is a subject which at present is in a state of flux, hardly having emerged from the realm of hypothesis, so that detailed consideration will profit little. At first the _modus operandi_ was explained and accepted as enzyme action, but it was soon evident, in view of the thermostability of the vitamine, that it could not be classed as a ferment or enzyme in the generally-accepted sense of this term. In general, it may be stated that there are two main views: one that the vitamine acts directly, and the other that it acts indirectly through the function of the endocrine glands. _Direct action_, furthermore, may be accomplished in at least one of three ways. The vitamine may (1) serve as a source of nutriment for the tissues, (2) exert an antitoxic effect on toxic products, or (3) function as a catalyzer. The first interpretation is evidently the simplest and conforms to the long-established knowledge of caloric food factors. That such small amounts as 2 c.c. of orange juice daily should suffice to protect an animal from nutritional disaster runs counter, however, to former conceptions of food nutrition. Further than this there is little against this viewpoint. In its favor is the fact that, up to a certain point, antiscorbutics act in direct ratio to the amount given; for example, 2 c.c. of canned tomato juice is insufficient to prevent scurvy in guinea-pigs, 3 c.c. will protect some but not all of a series, whereas when the amount is increased to 4 c.c. daily all animals will be saved. As we are considering new food factors it is manifestly unwise to judge them by old standards, and to decide offhand that they cannot possess such a high degree of nutritive power. This question must be regarded as still open.