YEAST AS A FOOD 85 



use for such masses of yeast plant has been found. In the 

 course of its growth the yeast plant stores up considerable 

 food material, and the masses of yeast that accumulate 

 prove to be a useful food material. It contains not only 

 the well-known types of food substance, proteins, fats, and 

 carbohydrates, but also is well supplied with vitamins.' 

 Vitamins, as is well known today, are very necessary food 

 substances, but of rather mysterious nature in that chem- 

 ists have never analyzed them. It is known, however, that 

 there are several vitamins, each serving its particular pur- 

 pose in animal nutrition ; not all of them are present in 

 yeast, but enough to make it a useful article of diet. The 

 various vitamins are distinguished by scientists by the 

 letters A, B, C, and so forth. Our knowledge of them is con- 

 stantly growing, and if recent claims are correct, that one of 

 the vitamins has been isolated in chemically pure form, more 

 accurate information about them will soon be forthcoming. 

 In spite of all the recent investigations, however, it must 

 still be admitted that our knowledge of their behavior in 

 the body, as well as of their chemical nature, is stiU very 

 imperfect. But it is known that they are necessary for 

 health ; and a diet without fresh vegetables, fruit, or miUc 

 is likely to be deficient in them. It is now well known that,' 

 when necessary, this deficiency may be made up, in part 

 at least, by eating yeast ; although for this purpose alone 

 there is little demand for it in ordinary civilized communi- 

 ties, because it is much less palatable than fruits, vege- 

 tables, or milk products. 



It is coming to be beHeved, however, that yeast has 

 other properties as a food less well understood even than 

 vitamins. Claims are even made that it overcomes con- 



