VI STATISTICS OF NUTRITION 271 



fresh protein material being supplied. If protein matter 

 be not supplied, the body must needs waste, because 

 there is nothing in the food competent to make good the 

 nitrogenous loss. 



On the other hand, if protein matter be supplied, there 

 is not the same necessity for any other but the mineral 

 food-stuffs, because protein matter contains carbon and 

 hydrogen in abundance, and hence is competent to make 

 good not only the breaking down which is indicated by 

 the nitrogenous loss, but also that which is indicated 

 by the other great products of waste, carbonic acid and 

 water. 



In fact, the final results of the oxidation of protein 

 matters are carbonic acid, water, and urea ; and these, 

 as we have seen, are the final shapes of the waste 

 products of the human economy. 



, Proteins contain in round numbers about 15 per cent. 

 of nitrogen, or a little more, and 53 per cent, of carbon, so 

 that the 20 grammes of nitrogen might be obtained from 

 130 grammes of protein, which would at the same time 

 introduce about 65 grammes of carbon. But the daily 

 waste of carbon is (about) 270 grammes, thus more than 

 200 grammes of carbon are still required to balance the 

 excess in the excreta. This additional amount of carbon 

 may be obtained from either fats or carbohydrates, 

 but preferably from a mixture of the two. Now 

 fats contain 80 per cent, of carbon, and carbohydrates 

 contain 40 per cent. ; thus the desired amount of 

 extra carbon may be obtained by adding to the 

 130 grammes of protein, about 50 grammes of fats 

 which contain 40 grammes of carbon and 400 grammes 

 of carbohydrates which contain 160 grammes of car- 

 bon. Adding to these 30 grammes of inorganic salts 

 and 2,300 grammes of water the total waste is about 

 balanced thus : — 



