THE IMEANING OF FOOD 103 



the chemistry of these regulators, but they have been grouped 

 together under the name vitamins. Three groups of vitamins 

 have been recognized. One, soluble in fats and oils, is called 

 fat-soluble A. The other two, which dissolve in water but not 

 in fat, are called water-soluble B and water-soluble C. It is 

 likely that as these substances come to be better known they 

 will receive more distinctive names based upon their composi- 

 tion, their actions, or their sources. For the present, however, 

 enough is known to guide us in the selection of food, especially 

 for infants and children and for those whose growth is not 

 proceeding satisfactorily. We know also that pellagra, beriberi, 

 scurvy, and probably other diseases result from the use of food 

 that lacks one or another of the vitamins. These have accord- 

 ingly been called deficiency diseases. 



Unlike proteins and the fuel nutrients, vitamins do not seem 

 to be universally present in all protoplasm. Still it may turn 

 out that it is only a matter of quantity. Vitamin A (fat soluble) 

 is most abundant in butter, or milk fat, in the yolks of eggs, in 

 cod-liver oil, and in certain vegetables (see table on page 105). 

 Water-soluble B is supplied by milk, tomatoes, lemons, spinach, 

 carrots, cabbage, onions, parsnips, potatoes, the common grains, 

 beans, and nuts. Yeast that has not been dried seems to con- 

 tain a large proportion of this vitamin. The C group occurs 

 most abundantly in cabbage, lettuce, tomatoes, lemons and 

 oranges, and in smaller quantities in spinach, fresh peas, onions, 

 and grapefruit. 



In comparing different foods with respect to vitamins two 

 interesting facts stand out. ( i ) Excepting eggs and dairy prod- 

 ucts, foods of animal origin have small or negligible quan- 

 tities of the vitamins. Cod-liver oil, which is rich in vitamin A, 

 is not commonly considered a food. (2) The cereals, which are 

 fairly rich in vitamin B, contain these substances chiefly in the 

 outer tissues, so that highly milled flour and polished rice are 

 almost wholly without these essential materials. 



79. Summary. From what has been said it should be clear 

 that the material intake of the organism bears an important 



