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Considering the outstanding importance of wheat to man, curiously few comprehensive studies of its chemistry have been made. It is, however, well known that variety, soil and climate all affect the chemical composition of wheat. Our knowledge of the subject was summarized in broad fashion by Booth, Carter, Jones & Moran (1941 a, b), whilst a detailed survey of the literature has since been published by Bailey (1944). Both these publications indicate the lack of precise information on the general chemistry of flours of different extraction prepared from the same wheat grist. This is clearly a problem of great importance, particularly in war time, when the rate of extraction must be fixed at that level which guarantees, in the diet as a whole, adequate amounts of those nutrients which are supplied by bread. Accordingly, a study of the changes in the composition of flour with change in extraction was undertaken jointly by the Research Association of British Flour-Millers (now the Cereals Research Station of the Ministry of Food), St Albans, and the Department of Medicine, Cambridge. WHEAT MIXTURES USED The following wheat mixtures have been milled and analyzed. (1) A typical all-Manitoba grist. The system of wheat marketing in Canada makes it comparatively easy to obtain a sample which may be taken as representative of Manitoba wheat. In order to do so, samples were obtained from 24 different shiploads of wheat reaching this country during the months of June, July and August 1943. These originated from five different ports on the Atlantic coast and two ports on the Pacific Coast. There were 12 samples ofNo. 1 Northern Manitoba and 12 samples of No. 2 Northern Manitoba. One

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FROM the results of previous work [Birch et al. 1937; Chick et al. 1938, 1, 2] it was concluded that young pigs could be reared successfully on a diet of maize and purified casein with the addition of a suitable salt mixture, provided that nicotinic acid were also given. Similar experiments made on rats showed that the addition of nicotinic acid was not required for this species [Chick et al. 1938, 2].The fact that an extraneous source of nicotinic acid or its amide does not appear to be required by the rat is responsible for the misleading results of researches into the aetiology of pellagra in which this animal was used. The dog, the pig and the monkey appear to resemble more closely the human being in their requirement of nicotinic acid in their food and consequently in their failure to maintain health on diets consisting too largely of maize.The vitamin requirements of different species of animals being so various, it seemed worth while to ascertain what other heat-stable, water-soluble, accessory factors in addition to nicotinic acid and riboflavin, are required by pigs. Whatever they may be, it is clear from our previous observations [Chick et al. 1938, 1, 2] that they are contained in whole maize in sufficient amount when it comprises 80 % of the diet.Edgar & Macrae [1937] have concluded that at least two other " B2-vitamins " are necessary for rats. One of these they call "ifiltrate", the other "eluate" factor. Fractions containing these two factors were originally derived from yeast but Edgar et al. [1938, 2] have also separated similar fractions, using somewhat modified methods, from a water-acetone extract of liver.In the present enquiry we are dealing with "filtrate fraction" and ''eluate fraction" as described by Edgar and Macrae and prepared by their methods. Fractions derived by similar methods from yeast, liver and rice polishings have been prepared by Lepkovsky et al. [1936] and by other workers. The relation of these to those employed by us will be discussed later. EXPERIMENTAL METHODSIt was first necessary to find a simple basal diet suitable for young pigs which would contain an adequate amount of vitamins A, D and E and of linoleic acid but which was as free as possible from water-soluble vitamins. To the basal diet a mixture containing vitamin B1 (aneurin), riboflavin and nicotinic acid, all ( 2207 )

A NOTICEABLE feature about the earlier studies of the " dermatitis " occurring in rats when they are deprived of the heat-stable B-vitamins has been the irregularity of its incidence. The occurrence of two different types of skin lesions developing under these conditions was foreshadowed in earlier work [Chick & Roscoe, 1928, p. 795; Chick & Copping, 1930, p. 933] and has been more clearly demonstrated in recent investigations. As the members of the vitamin B2 complex have gradually been separated from one another, and since vitamin B1 has been available in the purified state, it has been possible to use basal diets supplemented with relatively pure preparations of one or other constituent [see Gy6rgy, 1934; Chick et al. 1935; Copping, 1936]. Type (a) is a florid dermatitis, roughly symmetrical, with swelling and redness of the digits of the paws and of the ears, "spreading over the limbs and trunk with cracking and desquamation of the skin", the so-called "rat pellagra" originally described by Goldberger & Lillie [1926] and called "rat acrodynia" by Gy6rgy [Gyorgy et at. 1937]. In the present paper the expression " dermatitis." is reserved for this skin disease. The lesions of type (b) occur more particularly in the skin over the head and chest with loss of fur and without swelling or inflammation. The fur becomes very scanty, especially over the head and forearms, and appears moist and matted, with bald patches of skin developing later. The eyelids and the nostrils become inflamed and the former are often stuck together with a serous, reddish fluid, which also exudes from the nostrils. The wrists become stained with this fluid from continual rubbing against the nose and eyes, and patches of fur round the vagina or penis also become stained by soiling with the urine. With the discovery that riboflavin was a nutritionally active constituent of autoclaved yeast extracts and that the vitamin B2 complex could be separated into riboflavin and a "supplementary substance ",evidence was soon forthcoming that type (a) skin lesions developed on diets containing riboflavin and that riboflavin had curative value for skin lesions of type (b) [Gybrgy, 1934; Copping, 1936]. Similarly, type (a) dermatitis yielded to treatment with the " supplementary factor" in the vitamin B2 complex, which was called vitamin B6 by Gyorgy [1934]. This substance was found present in the " Peters's eluate " from charcoal as prepared from yeast extract. It was later found to be adsorbed from yeast on fuller's earth [Birch & Gy6rgy, 1936] and has since been separated in the pure