2. Marked deficiency in the supply of any vitamin leads to the development of a definite disease, e.g. rickets, and such a disease can be cured by giving a sufficient amount of the vitamin in a pure form. But there is evidence that a vitamin deficiency too small to produce the characteristic symptons of a deficiency disease will lead to vague and indefinite conditions of ill health. Individuals vary considerably in their requirements of individual vitamins. The recognition and evaluation of the symptons produced by a vitamin shortage too small to produce a typical deficiency disease is at present a major problem of nutrition studies, and is under active investigation by the Ministry of Health and the Medical Research Council.