Experiments have proved that an average man gives off grains of nitrogen and 4,700 grains of carbon daily,
and if he wishes to maintain his health this waste must be repaired. If he attempted to make up this loss by using one kind of food alone, it would be necessary to take much larger quantities of it than would be either
palatable or economical.
For example, suppose a man took nothing but bread. To obtain the 307 grains of nitrogen he would have to take more than four pounds, but by so doing he would consume 9,000 grains of carbon, nearly twice the quantity required. To obviate this a mixed diet is adopted. In this case z lb. of bread and | lb. of meat would supply the man’s daily requirements exactly.