THE ORIGIN OF LIFE 25 



they enrich the soil in which they grow without 

 themselves being dependent on the presence of any 

 nitrogenous bodies in solution. 



Bacteria are therefore to the green plant in 

 respect to nitrogen what the green plant is to all 

 other organisms in respect to carbon. Without the 

 assimilatory power of chlorophyll life would cease 

 from carbon-bankruptcy ; without the putrefactive 

 and nitrifying power of bacteria life would soon 

 cease from nitrogen-starvation. 



These elementary but fundamental facts of plant 

 and animal assimilation have been shortly outlined 

 here, because the question of the origin of life, 

 obscure as it is, would seem to centre principally 

 round the problem of assimilation, that power by 

 which life selects the elements necessary for its own 

 substance from the dead compounds around it, and 

 builds them up into its own integral body. 



It cannot be said that the progress of biology has 

 thrown any light on the problem of the origin of life. 

 Indeed, in former times, before the researches of 

 Redi, Needham and others had culminated in the 

 classical work of Pasteur, the spontaneous generation 

 of life from dead matter was generally held to be 

 a process of constant and everyday occurrence, so 

 that the origin of life might seem at any rate a 

 soluble problem. But now, when the doctrine of 

 spontaneous generation has been finally demolished 



