278 THE LESSON OF EVOLUTION 



roots , and from this various proteids , and ultimately 

 protoplasm, are formed. This is the process called 

 assimilation. Thus plants lay up a store of potential 

 energy in these carbon compounds, which they after- 

 wards use for purposes of growth. Animals feed on 

 these stores of potential energy, and they also use 

 them for the performance of actions. 



But how does mind move from the chlorophyll- 

 corpuscles without which carbonic-acid cannot be 

 decomposed at ordinary temperatures ? And how do 

 plants and animals make use of the store of potential 

 energy? They must in some way move the mole- 

 cules of protoplasm into new positions, so that 

 chemical affinity may be brought into action. We 

 say that mind orders the movements, but something 

 must start them. If we suppose that molecules are 

 always in movement, as in streaming protoplasm, 

 and that mind only directs those movements so as 

 to form new combinations, still energy is required 

 to alter as well as to originate movement. So that 

 mind must be capable of generating energy. This 

 is not more mysterious than matter being able to 

 generate energy through gravity and chemical 

 affinity. 



If mind can move the molecules of protoplasm in 

 an ordinary cell, we may suppose that it can move 

 them more rapidly in a nerve-cell, and with still 

 greater ease in the grey matter which forms the 

 cortex of the brain. It is this which may have given 

 rise to what we usually call intelligence in the higher 

 animals. But the healing of wounds and the forma- 

 tion of a cell-wall are purposive, and demand intel- 



