The Substance Which Is Alive in Plants 147 



his visible body but his invisible mind, which enables him to 

 plan and make use of tools, and harness the restless forces of 

 nature. So, we can only suppose that the physically-insignificant 

 protoplasm accomplishes its results by some analogous power. 

 Indeed, I venture for my part to believe that all protoplasm can 

 think, — not mind-thought it is true, for that appears to belong 

 only to man, but body-thought of which the mind is unconscious. 

 Or the matter may better be stated in this way, that man's thought 

 is but the conscious form of a principle which exists unconsciously 

 through all living substance. All protoplasm thinks, but only 

 the portion thereof in man's brain is aware that it thinks. How- 

 ever this may be, there is one thing that is plain; — man's is not 

 the only protoplasm which makes use of tools, and compels the 

 forces of nature to do its work, in evidence whereof let the reader 

 observe, for example, what is said in this book about enzymes, 

 and the dissemination of seeds. 



We must here turn back for a moment to the chemistry of 

 protoplasm in order to notice a matter important to an under- 

 standing of the relations of the substance to the external world. 

 The chemical complexity and instability of protoplasm render 

 it extremely sensitive to the effects of external influences, which 

 act upon it in three different ways. First, if strong enough, they 

 act upon it forcibly, precisely as upon any other substance of 

 comparable sort, and quite without reference to whether it is 

 living or not. Thus, heat burns it; pressure crushes it; and some 

 chemicals dissolve it. Second, the forces when too weak to exert 

 any forcible effects, can yet act inductively to promote, or to 

 check, some of the processes in progress in the complicated chemi- 

 cal laboratory which the living protoplasm actually is, and thereby 

 may produce a profound effect upon the behavior of the plant 

 as a whole. Thus heat, in a degree far too low to injure the 

 protoplasm, promotes the activity of those physical and chemical 

 reactions which underlie the streaming, nutrition, growth and 

 other activities of protoplasm; and this explains why protoplasm 



