126 THE HUMAN BODY. 



enough carbon, and in eating and absorbing it, and in 

 getting rid of the excess nitrogen (which is useless to him), 

 a great deal of useless labor must be thrust upon the 

 digestive and excretory organs. Were a man to live on 

 bread alone he would force much unnecessary work on his 

 organs. Bread contains little nitrogen in proportion to 

 its carbon,, and to get enough nitrogen far more carbon 

 than could be utilized would have to be eaten, digested, 

 and excreted daily. 



The human race has discovered this fact: men use, 

 where they have a choice, richly proteid substances to 

 supply the nitrogen needed, but derive the carbon mainly 

 from non-nitrogenous foods of the fatty or carbohy- 

 drate kinds, and so avoid excess of either nitrogen or 

 carbon. For instance, lean beef contains about J of its 

 weight of dry proteid, which proteid contains 15 per 

 cent of nitrogen. Consequently 1 pound 3 ounces of lean 

 meat would supply the nitrogen needed to compensate for 

 a day's losses. But the proteid contains 52 per cent of 

 carbon, so the amount of it in the above weight of fatless 

 meat would be 1070 grains (G9 grams) or nearly 2| ounces, 

 leaving 3150 grains (205 grams) or rather more than 

 seven ounces, to be got either from fats or carbohy- 

 drates. The necessary amount would be contained in 

 3940 grains (256 grams) or about 9 ounces of ordinary 

 fats, or in 7080 grains (4GO grams), a little over a pound, of 

 starch; hence either of these with the above quantity of 

 lean meat would form a far better diet both for the purse 

 and the system than meat alone. 



Explain why bread by itself would afford a bad diet. 



Why do men use a mixed diet? Explain why lean meat alone 

 would not be a good food. How could the deficient carbon of lean 

 beef be supplied? 



