40 PHYSIOLOGY AND NATIONAL NEEDS 



turbance in the nutrition of the nerves. A form 

 of neuritis occurs, with accompanying paralysis. 

 Now birds, when fed exclusively upon polished rice, 

 display this particular symptom in a very typical 

 manner, and the fact enables us to perform careful 

 controlled experiments, such as are necessary for 

 determining the distribution of the water-soluble 

 vitamine or, as it may also now be termed, the 

 " antineuritic " substance. After, say, three weeks 

 upon a diet of polished rice a pigeon or a fowl will 

 suddenly develop acute symptoms of paralysis. It 

 is quite easy to cure or prevent these symptoms by 

 adding other food-stuffs to the rice, and if known 

 amounts of them are added it is possible to estimate 

 approximately the relative richness of various foods 

 in this water-soluble or anti-neuritic factor. 



So much for the water-soluble vitamine. Is 

 now deprivation of the factor associated with fats 

 also followed by symptoms of actual disease ? The 

 experimental study of its effects is more difficult 

 than in the case of the other factor. Deprivation 

 of the latter is almost immediately felt ; but in their 

 own fat stores animals possess a supply of the fat- 

 soluble vitamine, and when it is absent from their 

 diet they seem able to mobilise this supply for the 

 purposes of their active tissues. Not till this in- 

 ternal store is exhausted, or reduced to some minimal 

 value, is its absence from the diet fully felt. Clearly, 

 different individuals will, either from differences in 



