Malnutrition of a specific type rarely, if ever, occurs uncomplicated in man or animals living on a diet of ordinary food-stuffs, even when the list of foods available is greatly restricted and the diet unsatisfactory to a pronounced degree. The specific deficiency diseases, with the possible exception of scurvy, can be produced as uncomplicated syndromes, only by carefully planned experimental diets. This will be evident to one who considers the nature of the deficiencies of polished rice and of muscle meats, the prominent articles in the diet of those peoples in certain countries, who suffer most from beri-beri. Such a diet is deficient in mineral elements to a degree that would in time greatly lower the vitality and shorten life. Its content of fat-soluble A is so low as to produce a borderline, if not an actual condition of keratomalacia. The defect which produces the most prompt and most visible pathological picture is that resulting from the lack of the anti-neuritic substance. Beri-beri appears, and overshadows in the eyes of observers, all other features of general malnutrition.

In the reported cases of xerophthalmia in man, the inference seems justified that, although many of the infants were doubtless suffering from latent scurvy and under-feeding, lack of sufficient fat-soluble A was a prominent factor in their malnutrition.