A HARD-WORKING DIET. 439 



APPENDIX. 



Note top. 340. 



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. 348. Extracts from Liebigs ( 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." (n). 



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 



