POOD 117 



It has been shown from experiments on men (and these 

 are naturally still by far the most reliable observations), 

 that the amount of food required for work over and above 

 the normal, is not met by a simple increase in proportion 

 to the amount of work performed. If, for example, one- 

 fifth of the total energy in food enables a man to perform a 

 normal day's work of 300 foot tons, the force-producing 

 value of any increase in diet to meet an extra hundred 

 foot tons, is not as high as a fifth, but falls to one-seventh ; 

 for the fifth hundred it would fall to one-ninth, and for a 

 sixth hundred to one-eleventh. 



This is the explanation of one of the difficulties in 

 attempting to lay down any hard and fast rule as to the 

 amount of work a given quantity of food can perform, and 

 renders the whole question, though of deep theoretical, but 

 of little practical importance. 



In the following table,* however, the amount of work 

 which a given amount of food can produce was ascertained 

 by direct experiment on the horse, the table is not only 

 interesting, but might be turned to practical utility in the 

 calculation of diets. 



1 lb. of the dry matter of hay produces 215 foot tons of work 



214 



In this table one must bear in mind the difference in the 

 digestive coefficients for the various foods ; for example, 

 one pound of maize produces more work than one pound of 

 oats, for the reason that 20 per cent, more maize is 

 digested than oats. 



* Wolff, op. cit. 



t It may appear strange that Wolff's table should show maize as 

 producing more work than beans, but his experimental animal only 

 digested 72 per cent, of the beans, which is below normal. 



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