144 The Living Plant 



and these yet others, in an almost endless succession. Thus liv- 

 ing protoplasm, complex and unstable in its constituents, and 

 acted upon constantly by diverse forces both from without and 

 within, is a constantly seething mass of energy-and-material 

 changes; — and it is such changes which constitute the visible 

 phenomena of life. But, — and here is the crux of the matter, — • 

 these changes are not hap-hazard and aimless, but on the contrary 

 proceed in a definite and orderly sequence, resulting in the forma- 

 tion of definite structures and the performance of definite actions 

 time after time and generation after generation; and it is this 

 orderliness, this definite procession of physical and chemical 

 processes, rather than anything in the processes themselves, 

 which is the most distinctive characteristic of life. The failure 

 of the regulatory power breaks the circuit of the processes, and 

 leaves the protoplasm a helpless mass of matter all ready for de- 

 cay; and this failure we name death. Life thus consists of two 

 elements, first, material and energy changes, that is, purely physi- 

 cal and chemical processes, whose general nature we can under- 

 stand, and which are seated in the various substances that chem- 

 ists have identified in the protoplasm, and second, a regulatory 

 power which directs and makes use of those processes but whose 

 nature and location is still quite unknown. Perhaps the nature 

 of this regulatory power is incomprehensible, or unknowable, in 

 our present philosophies, though as to that, science never admits 

 that anything is unknowable, but works ever under the assump- 

 tion that everything can be known if we but refine sufficiently our 

 methods of investigation. 



There is one other feature of the chemistry of protoplasm 

 which may have some importance in explaining its powers. In a 

 general way it seems true that the protoplasm of the higher and 

 more elaborate plants and animals is more complicated chemi- 

 cally, or at all events produces a greater number of complicated 

 substances (proteins especially), than the lower. This suggests 

 that each of the special physiological features successively ac- 



