48 BIOLOGICAL PROBLEMS 



safe one as far as beriberi is concerned. There need 

 be no fear, for instance, about eating white rice, since 

 the diet is so well protected in other quarters. 



In all these food-stuffs the anti-beriberi vitamine 

 appears to be well preserved. Dried eggs, dried 

 vegetables, dried milk, and yeast extract seem to be 

 as rich in the anti-beriberi vitamine as the fresh food- 

 stuffs, and it has not been possible to detect that there 

 is any appreciable loss in potency when these foods 

 are kept at room temperature. 



Nor is there much loss in value at the ordinary 

 temperatures of cooking, i.e. about 100 C. For 

 instance the value from this point of view of a food- 

 stuff is somewhat, but not seriously, diminished by 

 boiling for an hour. The anti-beriberi vitamine may 

 in fact be said to be comparatively thermo-stable. But 

 with higher temperatures it is a much more serious 

 matter. Cooking under pressure at 110-120 C. de- 

 stroys the vitamine more rapidly, and if this heating 

 is carried on for as much as an hour the degree of 

 impoverishment of the food-stuff in anti-beriberi vita- 

 mine may be extremely dangerous. This important 

 fact has its chief application when the diet consists, 

 to any appreciable extent, of tinned foods, which are 

 heated at a high temperature under pressure for con- 

 siderable periods in order to sterilize them. 



Thus a diet consisting of tinned foods and white 

 bread or rice, consumed over some months, would 

 undoubtedly lead to the ultimate development of beri- 

 beri. 



There are therefore two ways in which a diet is 

 likely to be rendered deficient in anti-beriberi vita- 

 mine: 



(a) By consisting too largely of over-milled cereals. 



(b) By consisting too largely of tinned, or, in any 

 other way, overheated food-stuffs. 



