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 

 v;^e 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 



