FITNESS 25 



ern chemistry, who by ingenious experiments 

 discovered that the essential feature of the 

 chemical process in the animal is combus- 

 tion or oxidation, and that the amount of oxy- 

 gen required by such combustion is not much 

 less than that needed to burn substances which 

 resemble the foods in the air. The problems 

 which thus arose have been studied by a 

 host of later investigators, notably by Liebig 

 and Voit, and gradually a vast array of facts 

 concerning the turnover of matter and en- 

 ergy in the body have been accumulated. 

 Among other achievements is the proof that 

 the principle of the conservation of energy 

 applies to the living organism. These have 

 been chemical investigations, carried out by 

 chemists, and for that reason, until quite 

 recently, they have not received their due 

 in general biology. 



Meantime, as knowledge of the balance 

 sheet of the body, the total metabolism so- 

 called, has been perfected, more and more 

 interest has developed in the changes which 

 attend the passage of matter and energy in 

 their various stages through the organism. 

 Such problems at once demand a physico- 

 chemical description of protoplasm as a nec- 

 essary basis for their solution. The same 

 demand has also arisen in other quarters. 



