56 THE NATURE OF LIFE 



amount of water and carbon dioxide, 

 whether fed to a dog, or burned in the 

 candle. 



In the candle flame we may point to 

 the spot where the combustion begins 

 and likewise where it ends. The ques- 

 tion arises. Can we do the same in the 

 case of the organism.'^ When food is 

 taken into the organism it is transformed 

 into living matter, after a time it again 

 becomes lifeless material. When and 

 how do these transformations take place? 

 We might regard the food as lifeless until 

 it becomes chemically active in the proc- 

 ess of combustion. We might also say 

 that when it ceases to be active in this 

 way it again becomes dead material. 



If we use this conception as a working 

 hypothesis we can at least give to our 

 ideas a certain degree of precision. It 

 will be seen that this involves the idea 

 that life is a process in which combustion 

 plays a fundamental role. This concep- 

 tion of life and of living matter leads us 

 to study it in precisely the same way as 



