PHYSIOLOGY 



and the mercantile marine. In our own day 

 similar deprivation, such as occurs in polar expedi- 

 tions, or during prolonged sieges, has led to out- 

 breaks of scurvy once more. 



On the ordinary mixed diet of the present 

 time, outbreaks of such deficiency-diseases do not 

 occur, because an element missing in one form of 

 food (e.g., white bread) will almost certainly be 

 supplied in another. The main danger in this 

 country is among the poor, unable to obtain sufficient 

 variety, and this is specially seen in the bringing 

 up of children when the chief fat supply may 

 be inferior cheap margarine. Rickets is far too 

 common to-day. Another danger manifested also 

 in children is infantile scurvy ; and this is caused 

 by the extensive use of sophisticated foods (in 

 which the vitamin has been destroyed) in place 

 of the foods, such as milk and fresh fruit, made 

 in Nature's laboratory. 



The small amount of the various vitamins which 

 is necessary is really marvellous, and makes one 

 wonder whether they will ever be separated in 

 quantities sufficient for analysis. I, however, am 

 an optimist, and believe that in the future these 

 difficulties will be overcome just as in the past, 

 when the outlook appeared to be as hopeless. 



To illustrate the small amount which is needed, 

 may I give you two definite examples ? 



My friend Professor Hopkins of Cambridge, 



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