VITAMIN A 225 



will be discussed more fully later. Further work of Osborne and 

 Mendel on this fat-soluble, growth-promoting substance (vitamin A) 

 showed it to be present in cod-liver oil, but absent in freshly pressed 

 almond oil (1914), and to be present in small amounts in beef fat 

 (1915a). When butterfat and beef fat were subjected to fractional crys- 

 tallization from alcohol, the active substance was found to be concen- 

 trated in the mother liquor or oil fractions rather than in the fractions 

 containing fats with high melting points. Heating butter with live steam 

 two and one-half hours did not destroy its potency in this connection, 

 nor did storage under ordinary conditions (1916). The butter oil, in 

 which the growth-promoting substance is more concentrated than in the 

 original fat, showed gradual deterioration, losing most of its potency in 

 a year. 



Meantime McCollum and Davis (1914) had shown that the growth- 

 promoting substance in butter was sufficiently stable to withstand the 

 saponification of the butterfat in alcoholic potassium hydroxide and 

 that it could be shaken out from the saponified material by olive oil. 

 In an attempt to determine whether the substance was carried by 

 vegetable materials as well as animal fats (1915) rats which had been 

 brought to a state of emaciation on a fat-free diet of casein, milk sugar, 

 dextrin, agar, and salts were brought back to a normal condition by 

 the substitution of corn meal for 50 per cent of the fat-free diet. Similar 

 results were obtained with wheat embryo (1915a), but less favorable 

 with whole wheat flour, rye flour, and oats. Reproduction was not se- 

 cured in any of these experiments. In the following year McCollum, 

 Simmonds, and Pitz (1916b) published results which indicated that oils 

 such as maize, cottonseed, linseed, olive, sunflower seed, and soy bean 

 oils in amounts up to from 10 to 20 per cent of the ration do not furnish 

 fat-soluble vitamin in appreciable amounts. On the other hand, alfalfa 

 and cabbage leaves were found to be excellent sources of the vitamin. 

 The cereal grains, while containing a small amount, were markedly 

 inferior to the alfalfa leaves. The authors concluded at that time that 

 "the superiority of the forage portion of the plant over the seed with 

 respect to its content of the fat-soluble A is of considerable interest 

 when viewed in the light of the dietary habits of lower animals. Those 

 which consume the forage rations grow successfully from generation to 

 generation on a strictly vegetarian diet, while the seed-eating animals, 

 so far as we have been able to learn, normally vary their diet to a 

 considerable degree by addition of green leaves, worms, insects, etc." 

 They further concluded from the observation that the ether-extracted 

 residue of corn meal is more effective in causing growth than is corn oil. 



