254 DIGESTION. 



food, the difficulty which, would otherwise arise from a 

 deficiency of carbon fat containing a large relative pro- 

 portion of this element, and no nitrogen. 



To take another example ; the proportion of carbon to 

 nitrogen in bread is about 30 to I . If a man's diet were 

 confined to bread, he would eat, therefore, in order to 

 obtain the requisite quantity of nitrogen, twice as much 

 carbon as is necessary; and it is evident, that, in this 

 instance, a certain quantity of a substance with a large 

 relative amount of nitrogen is the kind of food necessary 

 for redressing the balance. 



To place the preceding facts in a tabular form, and 

 taking meat as an example instead of pure albumen : 

 meat contains about 10 per cent, of carbon, and rather 

 more than 3 per cent, of nitrogen. Supposing a man to 

 take meat for the supply of the needful carbon, he would 

 require 45,000 grains, or nearly 6^1bs., containing : 



Carbon 4, 500 grains 



Nitrogen i>35o 



Excess of Nitrogen above the amount required 1,500 ,, 



Bread contains about 30 per cent, of carbon and I per 

 cent, of nitrogen. 



If bread alone, therefore, were taken as food, a man 

 would require, in order to obtain the requisite nitrogen, 

 3O,OOO grains, containing 



Carbon 9,000 grains 



Nitrogen 300 ,, 



Excess of Carbon above the amount required . 4,500 ,, 



But a combination of bread and meat would supply 

 much more economically what was necessary. Thus 



Carbon. Nitrogen. 

 15,000 grains of bread (or rather more than 



2 Ibs.) contain 4,5oogrs. I5ogrs. 



5,000 grains of meat (or about -| Ib.) contain 500 ,, 150 ,, 



5,000 300 



