WASTE AND REPAIR. 171 



uninterfered with. We have however in the lingering lives of 

 invalids who are able to take scarcely any nutriment, but 

 are kept warm and still, an illustration of the extent to 

 which waste diminishes as the expenditure of force declines. 



Besides the connexion between the waste of the organism 

 as a whole, and the production of sensible and insensible 

 motion by the organism as a whole ; there is a traceable 

 connexion between the waste of special parts and the activi- 

 ties of such special parts. Experiments have shown that " the 

 starving pigeon daily consumes in the average 40 times 

 more muscular substance than the marmot in the state of 

 torpor, and only 11 times more fat, 33 times more of the 

 tissue of the alimentary canal, 18*3 times more liver, 15 

 times more lung, 5 times more skin." That is to say, in 

 the hybernating animal the parts least consumed are the 

 almost totally quiescent motor-organs, and the part most 

 consumed is the hydro- carbonaceous deposit serving as a 

 store of force ; whereas in the pigeon, similarly unsupplied 

 with food but awake and active, the greatest loss takes place 

 in the motor-organs. The relation between special 



activity and special waste, is illustrated too in the daily 

 experiences of all : not indeed in the measurable decrease of 

 the active parts in bulk or weight, for this we have no means 

 of ascertaining ; but in the diminished ability of such parts 

 to perform their functions. That legs exerted for many hours 

 in walking, and arms long strained in rowing, lose their 

 powers — that eyes become enfeebled by reading or writing 

 without intermission — that concentrated attention unbroken 

 by rest, so prostrates the brain as to incapacitate it for think- 

 ing; are familiar truths. And though we have no direct 

 evidence to this effect, there is little danger in concluding that 

 muscles exercised until they ache or become stiff, and nerves 

 of sense rendered weary or obtuse by work, are organs so 

 much wasted by action as to be partially incompetent. 



Repair is everywhere and always making up for waste 

 Though the two processes vary in their relative rates, both 



