THE ACTIVITIES OF THE ORGANISM 119 



particle must be below a certain size in order to 

 be so affected. Are there organisms of this size ? 

 Undoubtedly there are, for many bacilli show Brown- 

 ian movements, while we have reasons for believing 

 that ultra-microscopic organisms exist. Also, on the 

 mechanistic hypothesis there are " biophors," the size 

 of which is of the same order as that of the molecules 

 of the more complex organic compounds. All these 

 must be affected by the molecular impacts of the 

 liquid in which they are suspended. Can they dis- 

 tinguish between the impacts of high- velocity molecules 

 and those of mean-velocity ones, and can they utilise 

 the surplus energy of the former ? This has been sug- 

 gested by the physicists. In Brownian movement, 

 says Poincare, ' we can almost see Maxwell's demons 

 at work." 



The suggestion is not merely a speculative one, for 

 it is well within the region of experiment. To prove 

 it experimentally we should only have to show that 

 the temperature of a heat-insulated culture of proto- 

 trophic bacteria falls while the organisms multiply. 



Is it not strange that the biologists, to whom the 

 Brownian movement is so familiar, should have failed 

 to see its possibly enormous significance ? Is it not 

 strange that the biologists, to whom the distinction 

 between the statistical and individual methods of 

 investigation is so familiar, should have failed to 

 appreciate this distinction when it was made by the 

 physicists ? Is it not strange that while we see that 

 most of our human effort is that of directing natural 

 agencies and energies into paths which they would not 

 otherwise take, we should yet have failed to think of 

 primitive organisms, or even of the tissue elements in 

 the bodies of the higher organisms, as possessing also 

 this power of directing physico-chemical processes ? 



