28 PHYSIOLOGY AND NATIONAL NEEDS 



I am to deal, however, with some facts which 

 indicate that, in one direction at least, practice, for 

 lack of knowledge, has for a long time been in danger 

 of going wrong. Experience might doubtless have 

 eventually corrected the error, but it may be hoped 

 that in this case scientific study will forestall ex- 

 perience, which is a much slower and more expensive 

 teacher. 



So long as a community can command not only 

 a sufficiency of food but also a variety of foods, and 

 uses these foods in fresh condition, as Nature made 

 them, appetite and instincts (if unperverted) are 

 usually sufficient to secure efficient nutrition for the 

 individual. But when natural foodstuffs are treated 

 artificially ; when, for instance, one kind of food 

 material is fractionated, and the consumer presented 

 with a part of it only, or when another material 

 is dried or heated for preservative or other purposes, 

 or, again, when natural foods are sealed up and kept 

 for long periods, it by no means follows that under 

 such conditions the food materials any longer 

 subserve proper nutrition, even though they 

 are eaten in sufficient quantity and satisfy the 

 appetite. 



Now questions of diet are proverbially liable to 

 stimulate quackery, and if I were here to discuss 

 the merits of " natural " foods without giving you 

 objective facts I might be suspected of merely 

 supporting certain doctrinaires self -dubbed " food 



