A HARD-WORKING DIET. 10g 
ACP PE NUDE XxX. 
Note to p. 10. 
The letters C, H, O, N, when used by chemists, 
stand not only for Carbon, Hydrogen, Oxygen, and 
Nitrogen, but for certain definite relative weights of 
them—the weights in which they combine with one 
another and with other elements. The letters thus 
used are called “symbols,” and the combining weight, 
though not expressed, is understood as included in 
the symbol. Each element has its symbol. For the 
purposes of this book it has not been requisite to enter 
into this; but in any elementary work on chemistry 
the combining weights of the elements will be found. 
Note to p. 18. Extracts from Liebig’s ‘Animal 
Chemistry’ on Oxidation. (ist Edition.) 
“ All vital activity arises from the mutual action of 
the oxygen of the atmosphere and the elements of the 
food.” (4). “The first conditions of animal life are 
nutritious matters, and oxygen introduced into the 
system.” (11). 
“ The consumption of oxygen in equal times may be 
expressed by the number of respirations. It is clear 
that in the same individual the quantity of nourish- 
ment required must vary with the force and number 
of the respirations.” (14.) “The number of respirations 
is smaller in a state of rest than during exercise or 
work. The quantity of food necessary in both 
conditions must vary in the same _ ratio.”. (15.) 
“Excess of food is incompatible with deficiency in 
