230 THE CAUSATION OF DISEASE. 



individuals differ markedly as to the degree of muscular 

 exercise requisite to maintain them in health. 



Let it not be supposed from these remarks that I would for 

 one moment counsel a life of muscular inactivity. Man in his 

 present state of evolution cannot expect to be a walking 

 brain. I have merely wished to point out that a considerable 

 degree of adaptation to a life of comparative muscular inac- 

 tivity might occur. Such adaptation can, however, only take 

 place in rare instances. It therefore follows that a fair amount 

 of muscular exercise is absolutely necessary to health and to 

 the full enjoyment of life. An enormous amount of suffering 

 might be averted by due indulgence in it. 



In regard to the quantity of muscular exercise needful to 

 health, each indivividual, as my remarks have already implied, 

 is a law in himself : some can lead more or less inactive lives 

 with impunity, nay, even with distinct advantage, while 

 others suffer much ill-health if circumstances do not permit 

 a large amount of bodily exercise. Over and over again I 

 have observed this among young men, chiefly of the muscular 

 kind, while working up for examination. The higher nerve 

 centres are then being spurred on to a great effort, while 

 the muscular system is kept in a state of almost complete 

 rest. Under these circumstances it not unfrequently hap- 

 pens that a mental gloom, among other evil effects, comes 

 over the individual ; but this, and, indeed, all the bad symp- 

 toms, are speedily removed by a brisk walk across country. 

 I have also frequently heard young men with a tendency to 

 uratic deposits observe that a good walk would clear the urine 

 and remove many unpleasant symptoms. 



It must not be supposed, on the other hand, that excess 

 of muscular exercise, even under the most favourable condi- 

 tions, as those of the agriculturalist, is an unmixed blessing. 

 Man was never intended to work like a horse ; his frame is 

 not constructed with a view to strength primarily. He has 

 evolved under conditions of moderate muscular exercise, and 

 such may be said to be the normal condition for the healthy 

 man. Other things being equal — constitution, food, hygienic 

 conditions — the hard-working farm labourer does not live 

 longer than the leisurely- working country squire. Doubtless, 



