Life as a Physical Phenomenon. 149 



If there is not an absolute line of classification in the 

 general outline of minerals, as compared with plants and 

 animals, we have but to advance one step and we find what 

 seems to be a remarkable and invariable difference. 



Plants and animals are always built up from cells, 

 minerals, never. 



Here then is our first absolute line of departure from 

 a common type in the construction of beings, and it may 

 be regarded as extremely doubtful whether we find 

 another. Between plants and animals, it is doubtful 

 whether there is more than the single distinction, a plant 

 deoxydizes, an animal oxydizes. 



Beings of neither of these classes are, where the typical 

 form exists, formed by simple accumulation of particles. 

 The assumption in most physiological works that minerals 

 are built by simple accretion of particles is not true ; but 

 there is a process, wonderful in its perfection, by which 

 certain particles, under certain circumstances, are arranged 

 in the form of a crystal, and certain other particles, under 

 certain other circumstances are made to constitute a cell. 

 That the cell differs widely from the crystal all must admit ; 

 but that there is less perfection in the arrangement of the 

 particles of the crystal than of the cell has never been de- 

 monstrated. 



That peculiar formative process by which particles or 

 molecules are arranged into cells has received various 

 names, which are perhaps well enough in themselves but 

 they have been so long used in a vague and undefined 

 manner that the idea conveyed is often, if not generally, 

 erroneous. 



The phenomena which distinguish plants and animals 

 from minerals are called collectively, life, or the vital process 

 — vitality — by which terms is usually understood far more 

 than seems to be indicated by the actual processes. Phy- 

 siologists, recognizing the difficulties attending the use 



