SEC. 4. ON DIET. 



§ 440. An ordinary man living an ordinary life will need 

 for the maintenance of vigorous health a certain amount of 

 food of a certain kind ; this we may take as a normal diet. 



Presuming that the experience of man has led him to adopt 

 what is good for him, we may ascertain approximately the 

 normal diet by means of the statistical method, by examining 

 the nature and amount of the daily food of a very large number 

 of individuals. The most valuable data for this purpose are 

 those gained by inquiries among persons who choose their own 

 food ; the results gained from the diets used in prisons or other 

 institutions, or among bodies of men such as the army, though 

 more readily arrived at, are open to the objection that the diets 

 in question are determined in part by the theoretical opinions 

 of those whose duty it is to fix the diet. Putting together the 

 various statistical results thus obtained, and selecting the quan- 

 tities which seem to be most commonly used rather than at- 

 tempting to strike a strict average or take a strict mean, we 

 find that in an ordinary diet for the twenty-four hours the 

 several food-stuffs are 



Proteids from 100 to 130 grms. 

 Fats „ 40 „ 80 „ 



Carbohydrates 450 „ 550 „ 



to these we must add 



Salts 30 grms. 

 Water 2800 „ 



The total (available) potential energy of the lower estimate is 

 2610, of the higher 3505 (kilogramme-degree) calories, calcu- 

 lated, in round numbers, on the data of § 421. With such a 

 statistical diet we may compare an experimental diet, that is to 

 say a diet arrived at through a series of trials on an individual 

 man whose body might be taken to be an average one, that diet 

 being considered a normal one in which the body, maintaining 

 vigorous health, neither gained nor lost in weight, and remained 

 moreover in nitrogenous equilibrium with the nitrogen of the 



658 



