A HARD-WORKING DIET. 25 
In the second place it is not for a moment to be 
expected that any one succeeds in calculating out his 
daily diet with the exactness of a scientific chemist 
making an analysis of a food, or conducting ex- 
periments on the amount of carbonic acid given off 
during work of a particular kind. Even with the 
most rigidly routine life any attempt to meet the 
daily needs with exactness would be upset by changes 
in the weather. The nearest approach to exactness 
is perhaps in training for boat-racing, but every one 
with any experience knows how a muggy day or 
roughish water will “take it out of you,” and make a 
slight increase of food necessary. 
The practical utility of the experiments—such as 
those referred to at p. 20, which these figures summa- 
rise—is that they show this—the more the muscular 
work done, the more carbonic acid and water are given 
off, and the more C and H must be taken into the 
blood for oxidation. These figures C 4,900, and 
N 300 give an average. (For N, see p. 28.) 
Knowing then the amounts of C, H, and N that From what 
sources can 
are needed, the next inquiry is the sources from our intakes be 
which these can be obtained. Side by side with the °"™"™? 
investigations mentioned above, many chemists were 
engaged in examining the chemical composition of 
many substances we use as food. 
Leaving out of consideration the various methods 
of giving the results, as this does not affect our present 
inquiry, the important point to look to is the total 
amount of C, H and N. 
It has been found that there is so important a dif- 
EB 2 
