O'SHEA — ASPECTS OF MENTAL ECONOMY. 163 



perior sort of recreation for a student, compared with euchre. 

 Bowling is doubtless better still ; and in short all pastimes in the 

 gymnasium or out of doors that make the motor element promi- 

 nent, are to be commended above those which are principally in- 

 tellectual. 



§3. Sleep. — In every living thing so far as we know periods 

 of repose alternate with periods of activity. There is a kind 

 of rhythm of action and of rest. Activity involves waste of liv- 

 ing substance and cessation of action is essential that recupera- 

 tion may take place. This rhythm is especially marked in hu- 

 man life. We have a long stretch, say sixteen hours, of waking 

 life, during which mind and body are active and energy is dis- 

 sipated ; then there supervenes a season of quiet, when worn out 

 tissue is repaired and the organism is brought back again to the 

 normal condition. This period of rest seems to be even more 

 important than nutrition for the preservation of life; for ex- 

 periments have been made upon dogs showing that death fol- 

 lowed more quickly from lack of sleep than from lack of food. 1 



Hodges' studies 2 demonstrating that in the case of animals 

 cerebral cells were depleted of their contents after a day's activi- 

 ties and restored during the quiescent period of the night are 

 suggestive respecting what in all probability takes place in prin- 

 ciple in the human brain. Waking life robs brain cells of their 

 substance ; then during sleep, when the mind is in repose, the 

 cells regain the energy which is essential for the sustenance of 

 activity. If a man be denied sleep so that the drain upon nerve 

 cells continues beyond a certain point, he will, of course, be 

 thrown into a condition of fatigue, when intellect and emotions 

 must suffer. It is then of vital consequence in student life that 

 periods of activity and rest be so alternated as to keep the nervous 

 organism in the best possible repair. 



Now, it has not been determined by exact experiment, so far 

 as I know, just how much sleep an individual needs. In all 

 probability this differs with different people. There have been 

 great historical personages, for instance, who have been able 



*I have lost my authority for this statement, but I remember clearly the ex- 

 periments and the outcome. 

 2 Loc. cit. 



