Process of Power Changes 23 



the learned things in our memories while we 

 learn other things. These learned things are a 

 load which requires mental power to carry, and 

 the increasing number of things we thus carry 

 is a measure of our growing mental power. 



The converse of the gain of powers by exer- 

 cise is the loss of powers by idleness, — the term 

 "idleness" meaning a reduced degree of activity 

 and not a total cessation of action. As a matter 

 of fact, gain and loss are two operations which 

 go on simultaneously in the body of each individ- 

 ual, but for simplicity we will consider them sepa- 

 rately. 



All plants raised for any considerable length 

 of time by division, like tubers, bulbs, cuttings, 

 buds or grafts, gain the power to produce roots 

 abundantly, and at the same time they lose the 

 power, sooner or later, to produce seeds. By con- 

 tinually exerting themselves along particular lines 

 plants develop new powers along those lines, and 

 by continued idleness along other lines (seed 

 production) they lose the power they originally 

 had. 



Man took wild plants, and, by continually 

 training them, developed their power of produc- 

 ing the things he wanted. 



