THE ORIGIN OF LIFE. 49 



is not so great as was once thought ; it has proved 

 that the animal body, and protoplasm in general, is 

 a machine making use of the chemical energy of its 

 foods ; it has shown that growth is little more than 

 chemical change, and that throughout the organic 

 world the same physical and chemical forces are at 

 play as in the inorganic world, only under more com- 

 plex conditions ; and it has rendered it probable that 

 most if not all of the vital properties are directly 

 dependent upon and explained by chemical and 

 physical forces. Science has, in short, proved that 

 living processes are a continuous change of chemical 

 and physical forces, and that what we mean by life is 

 something to direct this play of force. It then 

 assumes that this something is to be accounted for as 

 the property of protoplasm resulting from its com- 

 plex composition. This assumption is plainly a long 

 step in the region of hypothesis. But once made, it 

 becomes easy to posit and to explain by speculation 

 the spontaneous origin of life. For, indeed, it now 

 follows as a matter of necessity. The conclusion 

 which experiment forces upon us, that spontaneous 

 generation does not occur in nature to-day, is cast 

 aside as irrelevant to the more fundamental question. 

 For we ought not to expect, even if life originally 

 did appear mechanically, that it could do so now, 

 since the conditions are so different. Concerning the 

 first origin of life, science, therefore, knows nothing, 

 and is obliged to rest satisfied with the statement 

 that its original mechanical origin is an absolute 

 necessity of thought. " To hold the beginning of 

 life as an arbitrary creation is to break with the 



