92 THE VITAMINS 



Since yeast is rich in vitamin B, the introduction of yeast in the 

 making of bread must raise its vitamin content; but the increase is 

 only very sHght because the amount of yeast used is so small. The use 

 of a "lower" grade of flour (less purely the interior of the endosperm) 

 may be expected to increase the vitamin content of the bread much 

 more than does the yeast used for leavening. Successful attempts have 

 been made to raise the vitamin B content of bread through incorporat- 

 ing in the dough a concentrated extract of vitamin B and to increase 

 both this and other factors by the use of considerable amounts of 

 dried milk. 



As has been noted, cow's milk is relatively rich in vitamin G and 

 its use in bread making is thus of special value in supplementing 

 wheat and other cereal products, in this respect as well as in respect 

 to vitamin A and calcium, and in somewhat lesser degree vitamin B. 



Beans, peas, and seeds in general, when eaten entire or approxi- 

 mately so, are apparently all rather similar as sources of vitamin B. 

 McCollum states that with 25 per cent of white beans in the diet as 

 the sole source of vitamin B the supply was fully adequate for the 

 growth of rats. The requirement of barley was reported by Steen- 

 bock to be about 20 per cent, whole wheat by Bell and Mendel (1922) 

 from 20 to 30 per cent, and lentils by Jones and Murphy (1924) at 

 least 25 per cent of the ration. Osborne and Mendel (1919) speak of 

 whole wheat, soy beans, dried eggs, and milk solids as each being 

 required in proportions twice as large as of dried spinach, when serving 

 as sole sources of vitamin B. Green peas are considered by Eddy, 

 Kohman, and Carlsson (1926) to be richer in vitamin B, weight 

 for weight, than either milk or tomato juice. As noted previously, 

 considerable evidence has accumulated recently to the effect that seeds 

 contain relatively more of vitamin B than of vitamin G. Hauge and 

 Carrick (1926), Goldberger et al. (1926), and Hunt (1928a) have 

 shown this to be true for corn ; Smith and Hendrick ( 1926) for 

 rolled oats; Salmon (1927) for soy beans and velvet beans; Sherman 

 and Axtmayer (1927) and Hunt (1928a) for wheat; and Munsell 

 (1929) for rice polishings. 



Vegetables. — The potato was found by McCollum, Simmonds and 

 Parsons (1918a) to be capable of supplying all the vitamin B needed 

 by rats, but since large proportions of potatoes were used in all of 

 the experiments which they describe, their data do not show how the 

 potato compares with other foods quantitatively in this respect. Os- 

 born© and Mendel (1920a) found it to compare favorably with roots 

 as a source of vitamin B. Lyman and Blystone (1926), questioning 



