18 EVOLUTION OF LIVING ORGANISMS. 



number as science advances. If we analyse one by one 

 the distinguishing features of living matter, they can all 

 be paralleled in inorganic nature. No one universally 

 present in the first is universally absent in the second. 

 Complex chemical compounds, the properties of which 

 cannot be discovered in those of their component ele- 

 ments, cyclic changes of matter and energy, even self- 

 regulating mechanisms, occur in the non-living world. 

 As the untutored savage explains the movements of a 

 watch by attributing them to a spirit which has entered 

 into it, so many writers hold that the activities of living 

 matter are due to some special and mysterious vital 

 force. They attempt to bridge the gaps in our know- 

 ledge by merely giving them a name. This is no scientific 

 method ; science advances by explaining, that is de- 

 scribing, the unknown in terms of the known. If vital 

 force is merely a general term for those new properties 

 manifested in new mechanisms of increasing complexity, 

 there is no harm in it ; certainly living matter must dis- 

 play properties not found in simpler substances. But it 

 has no intelligible meaning if used to denote some force 

 added, so to speak, from without over and above the 

 ordinary properties, acting on the physico-chemical 

 mechanism but not of it. Like a vortex, the metabolic 

 process in living matter draws in inorganic substance 

 and force at one end, and parts with it at the other ; it is 

 inconceivable that these should, as it were, p^ss outside 

 the boundaries of the physico-chemical world, out of 

 range of the so-called physico-chemical laws, at one point 

 to re-enter them at another. 



When we maintain that the physico-chemical processes 

 of metabolism, with which are correlated all the pheno- 

 mena of life, form a continuous series without break, we 

 do not in the least mean to assert that this is a complete 

 and satisfying explanation of life from all points of view. 

 It is only one aspect of the problem, and the psychical is 

 another. Doubtless there are still other aspects within 



