WASTE AND REPAIR. 215 



hybernation, tlic proportion of 18.3 : 1. Among men and 

 domestic animals, the relation between degree of waste and 

 amount of expended energy, though one respecting which 

 there is little doubt, is less distinctly demonstrable; since 

 waste is not allowed to go on 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 illus- 

 tration of the extent to which waste diminishes as the ex- 

 penditure of energy 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 con- 

 nexion between the waste of special parts and the activities 

 of such special parts. Experiments have shown that " the 

 starving pigeon daily consumes in the average 40 times more 

 muscular substance that 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 energy ; 

 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 amount of 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 thinking; are familiar 

 truths. And though we have no direct evidence to this effect, 

 there is little danger in concluding that muscles exercised 

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