O SHEA — ASPECTS OF MENTAL ECONOMY. 



169 



Ore// nates = no of seconds fomemcr/je /6 attaife 



Fig. 16. — The ordinates show the number of seconds required to commit to 

 memory 18 digits. The abscissae show the progress of the hours as explained 

 above. (Patrick.) 



It is probable, to add a last word, that a student who studies 

 hard for say eight or ten hours has accomplished all that can be 

 done with profit or with safety without a long period of sound 

 sleep. Memory and reason will be more faithful and accurate 

 the following day if the mind be thus refreshed than if it be 

 driven on beyond the point of normal fatigue. And then when 

 exhaustion is reached it requires such a relatively long time 

 for recovery. 1 In normal fatigue a night's rest should bring 

 complete restoration ; but there is a point beyond this where the 

 cell seems to lose the power of ready recuperation and it takes 

 the spendthrift a long time to get back to himself, so to speak. 



J See Hodge, op. cit. 



