. 



GREAT STEPS IN EVOLUTION 75 



of digested food from the alimentary canal 

 into the blood-vessels, can be completely 

 described in terms of physical formulae. The 

 fact is that when we add up the components 

 revealed by chemical and physical analysis, 

 they do not amount to the whole resultant 

 which we see in a vital action, even of a 

 simple sort. 



It is indeed profitable to compare a living 

 creature to a machine, and a fertile method 

 of discovery to press this comparison to its 

 hardest. Yet the living organism differs 

 from any machine in its greater efficiency; 

 and especially in this, that the transfer of 

 energy into it is attended with effects con- 

 ducive to further transfer and retardative 

 of dissipation. Again in this, that it is a 

 self-stoking, self-repairing, self-preservative, 

 self-adjusting, self -increasing, self -reproducing 

 engine ! And this also must be remembered 

 in comparing a living creature and a machine, 

 that the latter is no ordinary sample of the 

 inorganic world. It is an elaborated tool, 

 an extended hand, and has inside of it a 

 human thought. It is because of these 

 qualities that highly complex machines come 

 to be jso like organisms. But no machine 

 profits by experience, nor trades with time 

 as organisms do. Therefore it is that the 



