194 AN AGRICULTURAL WAR PROBLEM 



This could only be fat. Since fat contains 76 per 

 cent, of carbon, the amount of fat stored could be 

 calculated from the difference between the carbon 

 in the food and the carbon in the excreta. This 

 figure was not quite exact, since comparison of the 

 nitrogen in the food and in the excreta showed that 

 a trace of protein was also stored, which must con- 

 tain a trace of carbon. This could easily be allowed 

 for, since protein contains 16 per cent, of nitrogen 

 and 53 per cent, of carbon. Having applied this 

 correction it was found that the addition of 1000 

 grams of starch to the maintenance diet caused the 

 production in the body of 250 grams of fat. 



The animal was now placed once more on his 

 maintenance ration and after an interval this was 

 increased by the addition of 1000 grams of some 

 other food, say linseed cake. Applying the same 

 methods it was found that 1000 grams of linseed 

 cake caused the production in the body of 192 

 grams of fat. 



From these results the starch equivalent of 

 100 Ib. of linseed cake for fat production is evi- 

 dently 100 x 192 -f- 250, or 77 Ib. of starch. 



Experiments of this kind are extraordinarily 

 troublesome and very expensive. Nevertheless 

 Kellner was able to carry through enough of them 

 to enable him to assign starch equivalents to some 

 300 foods. These were not all based directly on 

 separate experiments, but the experiments carried 

 through provided a basis for calculation. It was 



