244 AGE, GROWTH, AND DEATH 



number of lessons, ending in failure, for a person at 

 seventy. It would have been scientifically interesting 

 to have kept an exact record of the period of time 

 which it took at each age to learn bicycling, but I 

 think enough has been said to convince you that if we 

 could acquire such a measure of psychological develop- 

 ment as would enable us to express its rate in figures, 

 we should be able to construct a curve like the curve 

 which I showed you in the third lecture illustrating the 

 decline in the rate of growth, and we should see that 

 during the early years of life the decline in the power 

 of learning was extremely rapid, during childhood less 

 rapid, during old age very slow. But the great part 

 of the decline would occur during early years. 



Here we see the principle of stability, in maturity, 

 which we see also illustrated in structure and growth. 

 The mind acquires its development; it retains that de- 

 velopment in the adult a long time. But surely there 

 comes a period when the exercise of the mind is diffi- 

 cult. It requires a great effort to do something new 

 and unaccustomed. A sense of fatigue overwhelms 

 us. I believe that this principle of psychological de- 

 velopment, paralleling the career of physical develop- 

 ment, needs to be more considered in arranging our 

 educational plans. For if it be true that the decline 

 in the power of learning is most rapid at first, it is 

 evident that we want to make as much use of the early 

 years as possible that the tendency, for instance, 

 which has existed in many of our universities, to post- 

 pone the period of entrance into college is biologically 



