454 VEDDER AND CLARK. 



of nervous tissue. Moreover, a certain amount of this vitamine 

 is necessary for each fowl constantly as is shown by the fact 

 that degeneration of the nerves may be demonstrated within 

 seven days after the supply of this vitamine is cut down by a 

 polished rice diet. The amount necessary, however, varies for 

 different fowls according to their individual idiosyncrasy, be- 

 cause, as has been shown, some fowls are more susceptible to this 

 deficiency than others. If the supply of vitamine is cut down by 

 feeding on polished rice, or any other dietary which contains an 

 insufficient amount of this substance, the normal metabolism of 

 the nervous system at once suffers. Should this faulty diet be 

 continued, the degeneration of the nervous system progresses 

 steadily, until a point is finally reached when the symptoms of 

 polyneuritis appear. Even though the amount of this necessary 

 substance is reduced only very slightly below the quantity essen- 

 tial for a given fowl, degeneration occurs though more slowly, 

 and the symptoms of neuritis will appear if the reduction be con- 

 tinued for a sufficient length of time. 



The question naturally arises if this vitamine is essential to 

 normal nervous metabolism, why are any fowls on a polished 

 rice diet protected from polyneuritis gallinarum and any men 

 from beriberi? This is probably due to the fact that the meta- 

 bolic processes are much more active in some individuals than in 

 others. Those fowls whose metabolic processes are very active 

 require larger amounts of vitamine, and succumb most promptly 

 on a diet of polished rice. In those fowls whose metabolic proc- 

 esses are more sluggish, the incubation period is longer. It is 

 probable that even polished rice contains a trifling quantity of 

 this vitamine in comparison with other food. Therefore, some 

 fowls whose metabolism is exceptionally sluggish may be able to 

 subsist for some time on this polished rice without developing 

 neuritis. However, in most cases this protection is not complete 

 as is shown by the fact that degeneration may be demonstrated in 

 their nerves, although they are apparently in good health. Prob- 

 ably in most instances the protection apparently enjoyed by some 

 fowls on polished rice is only partial, and if the diet be continued 

 long enough practically all will succumb. The interesting case 

 related by Eijkman where the fowl developed neuritis only after 

 a year's feeding is a case in point. The same explanation will 

 account for the fact that some men are more susceptible to beri- 

 beri than others and that some are apparently exempt. From 

 the fact that the incubation period in man averages three or 

 four months as compared with only twenty-six days in the fowl, 



