ACCESSORY FOOD BODIES in 



As we shall see in a later chapter, these experi- 

 ments do not stand alone. They are confirmed not 

 only by other experiments definitely undertaken to 

 test the effect of the Phosphotungstic and Silver 

 nitrate fractions, but the whole series of the experi- 

 ments made with the treated peat becomes intelli- 

 gible when considered in relation to the accessory 

 food bodies. 



In describing the results obtained it has seemed 

 simpler so far to draw only a slight distinction 

 between the vitamines, as described by Funk, and 

 the accessory food substances, as described by 

 Hopkins. There is a close similarity between the 

 two classes of bodies, in that both are prepared by 

 means of Phosphotungstic acid and Silver nitrate 

 from such substances as the husk of grain, yeast, 

 egg-yolk, milk, and so forth. There are, however, 

 certain differences. Thus, for instance, whereas the 

 vitamines of Funk appear to be in the nature of a 

 pyrimidine base, in the experiments made by Hop- 

 kins it was insisted that the bodies used were free 

 from amino-acids, purine and pyrimidine bases. It 

 should be noted also that, like Hopkins's bodies, the 

 plant accessory substances are resistant to heat. 

 This is shown by the fact that after the Phospho- 

 tungstic extract from bacterized peat had been 

 treated in an autoclave at 134 C. for half an hour, 

 it still gave the characteristic scum reaction (vide 

 later this chapter) . At present analytical difficulties 

 make it unwise to dogmatize on this point. What 

 has to be emphasized is that the treated peat con- 

 tains substances which are able to promote growth 



