70 THE STORY OF LIFE'S MECHANISM. 



But the fact is, when we turn our attention in 

 these two directions, we find the result is the 

 same. . If we look for the lowest organisms we - 

 find them among forms that are made of a single 

 cell, and if we analyze the tissues of higher 

 animals we find the ultimate parts to be cells. ' 

 Thus, in either direction, the study of the cell is 

 forced upon us. 



Before beginning the study of the cell it will 

 be well for us to try to get a clear notion of the 

 exact nature of the problems we are trying to 

 solve. We wish to explain the activities of life 

 phenomena in such a way as to make them intel- 

 ligible through the application of natural forces. 

 That these processes are fundamentally chemical 

 ones is evident enough. A chemical oxidation of 

 food lies at the basis of all vital activity, and it is 

 thus through the action of chemical forces that 

 the vital powers are furnished with their energy. 

 But the real problem is what it is in the living 

 machine that controls these chemical processes. 

 Fat and starch may be oxidized in a chemist's test 

 tubes, and will there liberate energy ; but they 

 do not, under these conditions, manifest vital 

 phenomena. Proteid may be brought in contact 

 with oxygen without any oxidation occurring, 

 and even if it is oxidized no motion or assimi- 

 lation or reproduction occurs under ordinary 

 conditions. These phenomena occur only when 

 the oxidation takes place in the living machine. 

 Our problem is then to determine, if possible, 

 what it is in the living machine that regu- 

 lates the oxidations and other changes in 

 such a way as to produce from them vital 



