VITAMIN B (B^) 95 



Using pigeon tests, Plimmer, Raymond and Lowndes (1929), 

 have found pulses and nuts to have the following vitamin B potencies, 

 taking the value of dried yeast as 100: Split peas, whole dried green 

 peas, lentils, and soya beans, 13 ; haricot beans, ground almond, whole 

 almonds, and dried chestnuts, 10; hazelnuts and peanuts, 20; cocoanut 

 and roasted coffee, 0. 



Quantitative Determination 



As explained earlier in this chapter, two methods have been chiefly 

 employed in work with vitamin B, namely (1) the prevention or cure 

 of polyneuritis in fowls, pigeons, or other birds, and (2) the pro- 

 motion of growth in young experimental animals, most frequently rats. 



For a time, attempts were also made to utilize the rate of growth, 

 or rate of reproduction, of yeast as a simpler and more rapid method 

 of testing foods for vitamin B values; but such stimulation of yeast 

 is now considered as a measure of "bios" rather than of vitamin B 

 value. Bios has been shown to be relatively stable both to alkaU and 

 to heat (Guha and Drummond, 1929), which properties differentiate 

 it from vitamin B (Bi). In view of this fact and the pressure for 

 space to review here the present knowledge of the substances univer- 

 sally regarded as vitamins, we are regretfully obliged to omit discus- 

 sion of bios and of the yeast method, and to confine attention here 

 to a very brief mention of the pigeon method of testing for antineuritic 

 values of foods and a fuller account of the rat growth method as 

 the one chiefly used in attempts to measure quantitatively the relative 

 amounts of vitamin B in different materials or in the same material 

 before and after different treatments, as in the studies of stability 

 summarized further on in this section. 



Quantitatively, experiments with rats have usually seemed more 

 satisfactory than those with pigeons. Cure of the polyneuritis induced 

 by a polished rice diet is qualitatively a striking demonstration; but 

 there is no satisfactory way of determining the degree of polyneuritis 

 from the symptoms or of judging the exact time at which the curative 

 experiment should be performed in order to justify quantitative com- 

 parisons of the amounts of foods (or other materials) required to 

 effect a cure. It may readily happen that a vitamin-containing food 

 which shows good antineuritic effects upon one bird may fail to cure 

 a second because in the second case the disease had progressed so far 

 as to preclude recovery. Still greater difficulty arises from the fact 

 that birds which have developed typical polyneuritis on vitamin-free 

 or vitamin-poor diet sometimes recover spontaneously without any 



