On the Scientific Study of Human Nature, 477 



the brain and the solar system march together. Exercise 

 and repose are equally indispensable to mental vigour ; 

 deficiency of exercise produces mental feebleness ; de- 

 ficiency of rest, disease. But there lurks in this statement 

 a deeper and more dangerous meaning than at first 

 appears. The equilibrium once lost is most difficult to re- 

 store — there is a fatal persistence in the morbid state. It 

 is a general law of the animal economy, that when the vital 

 powers are from any cause depressed below a certain 

 point, they are not easily, and sometimes are never, re- 

 paired. A large loss of blood, or a profound exhaustion, 

 may entail effects upon the constitution which will last for 

 years, perhaps for life. As might be expected, the brain 

 illustrates this principle more impressively than any other 

 portion of the system : if worked beyond its limits, there is 

 produced a rapid exhaustion of power which renders re- 

 pose impossible. The exhaustion of overwork is accom- 

 panied by excitement, which tends to perpetuate the work 

 and accelerate the exhaustion. The will is thus swamped 

 in the uncontrollable mobility of the automatic system, the 

 attention becomes insanely exalted, the brain will not be 

 ordered to rest, and words of warning are wasted. When 

 his physicians admonished Sir Walter Scott of the impend- 

 ing consequences of excessive mental labour, he sadly re- 

 plied : " As for bidding me not work, you might as well tell 

 Molly to put the kettle on the fire, and then say ' Now don't 

 boil' " 



We live in an age of intense mental activity and ever- 

 increasing cerebral strain. Steam and electricity are 

 tasked to bring daily tidings of what is happening lW over 

 the world, and impressions pour in upon the bram at a rate 

 with which nothing in the past is comparable. The fierce 

 competitions of business, fashion, study, and political am- 

 bition, are at work to sap the vigour and rack the integrity 

 of the mental fabric, and there can be no doubt that there 



