The importance of having the inorganic content of the diet properly constituted is shown especially well in the histories of the mothers 983 and 1978 (1). The former was fed rolled oats supplemented with both fat-soluble A (supplied as butter fat), and purified protein in the form of casein. Even with these two additions she was able to induce in her young less than half the normal growth. The young began to die at the age of 45 days and succumbed in rapid succession. Rat 1978, on the other hand, whose diet consisted of rolled oats supplemented with a suitable salt mixture and butter fat, was able to produce milk which induced growth in her litter at about two-thirds the maximum rate observed in the case of well fed mothers. The improvement of the milk by the inclusion of fat-soluble A in the diet was very apparent, since the young were able to live beyond the period of the sixty days covered by the experiment. These observations support the view that fat-soluble A cannot be synthesized by the mammary gland.

The experience of rat 1019, Chart 9, whose diet consisted of rolled oats supplemented with purified protein and a suitable salt mixture, showed that the mother was able to induce in her young nearly normal growth during a period of thirty days, although her diet was very poor in fat-soluble A. It should be borne in mind that the seeds, because they contain a small proportion of cellular structures in addition to their reserve food package in the endosperm, contain but a small and inadequate amount of fat-soluble A. The mother is able, when her diet of oats is corrected with respect to two factors, protein and salts, to concentrate in the milk the small amount of fat-soluble A in her food, and perhaps to supplement this in some degree with the reserve in her own fatty tissues. In this way she is able to bring the young to a state of relative independence while she herself is subsisting on a food supply not capable of inducing any growth whatever in the young. There is abundant experimental proof that when the protein and the inorganic contents of the diet are satisfactory, animals can maintain themselves for a long period on a supply of fat-soluble A too small to prevent xerophthalmia in animals whose diets are more poorly constituted in respect to other factors.