58 THE STORY OF THE LIVING MACHINE. 



be a hopeless task. We are well acquainted with 

 forces adequate to the formation of chemical 

 compounds. If the force of chemical affinity is 

 adequate under certain conditions to form some 

 compounds, it is easy to conceive it as a possi- 

 bility under other conditions to produce this 

 chemical living substance. Our search would 

 need then to be for a set of conditions under 

 which our living compound could have been pro- 

 duced by the known forces of chemical affinity. 



But suppose, on the other hand, that we find 

 this simplest bit of living matter is not a chemical 

 compound, but is in itself a complicated machine. 

 Suppose that, after reducing this vital substance 

 to its simplest type, we find that the substance 

 with which we are dealing not only has complex 

 chemical structure, but that it also possesses a 

 large number of structural parts adapted to each 

 other in such a way as to work together in the 

 form of an intricate mechanism. The whole prob- 

 lem would then be changed. To explain such a 

 machine we could no longer call upon chemical 

 forces. Chemical affinity is adequate to the ex- 

 planation of chemical compounds however com- 

 plicated, but it cannot offer any explanation for 

 the adaptation of parts which make a machine. 

 The problem of the origin of the simplest form of 

 life would then be no longer one of chemical but 

 one of mechanical evolution. It is plain then that 

 the question of whether we can attribute the prop- 

 erties of the simplest type of life to chemical 

 composition or to mechanical structure is more 

 than a formal one. 



The Discovery of Cells. It is difficult for us 

 to-day to have any adequate idea of the wonder- 

 ful flood of light that was thrown upon scientific 



