22 Process of Power Changes 



have been found in the leaf stalks of black helle- 

 bore after five days of physical training. 



The Binet system is used to measure the men- 

 tal development of children. To measure any- 

 thing it is necessary to have a standard for com- 

 parison. By testing a good many children, the 

 Binet system establishes a certain degree of men- 

 tal development as representing normal-minded- 

 ness for a five-year-old child ; a higher degree of 

 mental development as representing normal-mind- 

 edness for a six-year-old ; a still higher degree of 

 mental development as representing normal-mind- 

 edness for a seven-year-old; and so on. 



The Binet system does not extend its standards 

 into the mature years of adult life because the 

 tests used are not suitable for that purpose, but 

 we can reach the matter in another way. It re- 

 quires mental power to learn a thing and re- 

 member it while learning a second thing. It 

 requires more mental power to remember two 

 things while learning a third; more yet to re- 

 member three things while learning a fourth; 

 still more to remember four things while learn- 

 ing a fifth; and so on. From youth to old age 

 we are continually learning things, and we carry 



