CH. XXX.] UNKNOWN BUT ESSENTIAL CONSTITUENTS OF FOOD 491 



Unknown but Essential Constituents of Pood. 



If an animal is fed upon a mixture of pure protein, fat, and 

 carbohydrate, with a due admixture of salts and water, it does not 

 thrive, but shows evidence of malnutrition, although the quantities 

 given may be theoretically correct. If a growing animal is fed on 

 such a diet it ceases to grow. But if, as Hopkins showed recently, 

 a small amount of a natural food, such as milk, is mixed with the 

 artificial diet just referred to, the animals thrive and grow normally. 

 There is something extra, something which is at present unknown, 

 which is absolutely essential, and quite small amounts of it are 

 usually sufficient. 



If this unknown constituent is absent from a man's diet, he 

 undergoes just the same sort of malady, and illnesses so produced, 

 such as scurvy and Beri-beri, are termed " Deficiency diseases." 



A good deal of work has recently been done in relation to one 

 of these diseases, namely, Beri-beri (the Kak-ka of Japan). This 

 is prevalent among the natives whose staple article of diet is 

 polished rice, that is, rice grains deprived of their external layer. 

 This disease is characterised by malnutrition of the nerves, and 

 neuritis or inflammation of the nerves is followed by nerve-degenera- 

 tion and paralysis. It can also be produced in birds by feeding 

 them on polished rice ; and in both man and bird can be rapidly 

 cured by adding the polishings of the rice grains. The outer layer 

 of the grain contains the extra something, and Funk and others have 

 recently separated out from the polishings a base which they have 

 termed vitamine, although at present there is no certainty of its 

 chemical composition. At any rate this base is the curative 

 principle, and very small doses will cure the condition. 



Vitamine is not confined to rice grains, but is found in many 

 other vegetable and animal foods. The value of whole meal bread, 

 for example, does not depend on the small extra amount of protein 

 it contains, but probably here also upon vitamine. The amount 

 of vitamine varies considerably. Thus, in pigeons fed upon polished 

 rice, as much as 20 grammes of meat daily must be added to prevent 

 the occurrence of Beri-beri ; whereas 3 grammes of egg-yolk are 

 sufficient, and half a gramme of yeast is enough. 



