342 GAEL VOEGTLIN 



portion of the well-known food factors (purified proteins, fats, carbo- 

 hydrates and inorganic salts). These attempts invariably resulted in 

 failure, as the animals after a certain period declined in weight and ex- 

 hibited symptoms of malnutrition. Pioneer work on this subject was 

 donebyLunin (1881), Stepp(a)(6) (1909, 1912), Hopkins(a) (1912), 

 Osborne and Mendel (1911), and McCollum and Davis(d) (1912, 1915). 1 

 The addition of small quantities of milk or certain other natural foods to 

 the purified diet.rendered the latter physiologically complete. The purified 

 diet, as the diet which causes beriberi or scurvy, was evidently lacking in 

 some food constituents which are essential for normal metabolism. These 

 substances of unknown chemical composition were termed by Funk "vita- 

 mins." Hopkins refers to them as "accessory food factors," and McCollum 

 speaks of the "Fat-soluble A" (fat-soluble vitamin), "Water-soluble B" 

 (antineuritic vitamin), to which Drummond has added the "Water-soluble 

 C" (antiscorbutic vitamin). 



There can be little doubt, if any, about the identity of the antineuritic 

 vitamin with the water-soluble B. The proof for this assumption is 

 based upon two well established facts: (1) the solubilities in various 

 solvents and the resistance towards heat, exposure to alkali and other 

 agents is identical for both substances; and (2) the distribution of these 

 two factors in various foodstuffs is the same, whether established by 

 means of growth experiments on rats or whether the antineuritic power is 

 determined in pigeons. Both pigeons and rats develop polyneuritis if the 

 diet is lacking in either water-soluble B or antineuritic vitamin. 



All the various terms applied to these substances have been justly 

 criticized for one reason or another. The terminology adopted in this 

 chapter should therefore be considered as more or less arbitrary. 



Chemical Nature and Physical Properties of Vitamins 



The chemical composition of vitamins is unknown, principally on 

 account of past failures to isolate these substances in pure form from the 

 natural foods. The work so far done on this subject is, however, not 

 without interest, both from a theoretical and practical aspect, and will 

 therefore be briefly reviewed. 



Antineuritic Vitamin (Water-soluble B). The early researches on 

 beriberi and polyneuritis gallinarum showed that the antineuritic vitamin 

 can be readily extracted by means of water or hot ethyl alcohol (Eijkman 

 (e), 1906) from rice polishings, yeast, and other material rich in this sub- 

 stance. Acetone, ether, chloroform, benzene, and petrolether fail to ex- 



1 For a historical review of the earlier experiments, the reader is referred to the 

 monograph by Osborne and Mendel (1911). The later development of the subject is 

 admirably presented in the "Report on the Present State of Knowledge Concerning 

 Accessory Food Factors (Vitamins)," Medical Research Committee, 1919, H. M. Sta- 

 tionery Office, Imperial House, Kingsway, London, W. C. 2. 





