758 POPULAR SCIENCE MONTHLY. 



The differences in the susceptibility of different persons to 

 fatigue are very interesting. Every person, as a rule, possesses a 

 course of efficiency peculiar to him, which works itself out in the 

 same manner during any particular period of labor. Some dis- 

 play in single efforts first an increase and then after some time a 

 decrease of efficiency; they are least readily fatigued. Others, 

 registering a depression of efficiency after the first quarter of an 

 hour, betray a very great susceptibility to fatigue. All the tran- 

 sitions are observable between these two forms, but each individ- 

 ual generally follows the same course according to his personal 

 peculiarity. 



The susceptibility to fatigue is observed in all possible exami- 

 nation tasks, and may therefore be considered to represent a bot- 

 tom principle of the individual personality, which, while it may 

 be influenced within certain limits, as a general rule measurably 

 determines the capacity of men for work. 



Other means of measuring the capacity of a subject are af- 

 forded by the ease with which he is diverted from his task, or his 

 susceptibility to disturbing influences from without and from 

 within ; his elasticity, or the readiness with which he recovers 

 from the effects of fatigue or diversion ; and the way he is affected 

 by taking food, physical exercise, and the time he has for sleep. 

 In each and all of these fields of inquiry the result obtained 

 has to be complemented finally by the estimation of the quali- 

 tative value of the work accomplished. 



We may infer from this passing review that it is actually pos- 

 sible to express important properties of mental personality in 

 measurable, generally comparable, determinations. But we are 

 still far from being able to apply such measurements to the pur- 

 poses of daily life. Yet, while we fail if we attempt to draw cer- 

 tain lessons from the matured, complicated organization of the 

 grown-up man, the simpler, still growing mental equipment of the 

 child affords a more fruitful field for study and is more subject to 

 our influence. 



The question then presents itself for investigation of the men- 

 tal endurance of our school children. The school requires its 

 pupils to perform daily a specified amount of mental work, while 

 it is really not clearly known whether the childish brain is actu- 

 ally able to fulfill the demand without suffering lasting damage. 

 The young men I experimented upon, whose facility in addition 

 fell off at the beginning of the second hour, had already had their 

 working powers exercised and tested by responding to the demand 

 of the school and of the university. Against them was a child 

 two years old, who gave plain evidences of weariness after only a 

 few minutes of fixed attention. Valuable researches on this sub- 

 ject have been made by Prof. Burgerstein, of Vienna, who com- 



