14 DECAY. 



not arrived at maturity, the addition is greater than the 

 loss, and so there is growth. The renewed part, too, is 

 more perfect than that which preceded it, and thus there 

 is development also. 



Even when growth and development have ceased, there 

 is no cessation of change. Life is not, as was once thought, 

 the power of resisting decay. On the contrary, the waste 

 which occurs in a living body, is incessant ; and in propor- 

 tion as life is more active, so is decay. But while with the 

 waste of a dead thing, there is no corresponding repair, in 

 the case of the living, destruction and renewal advance 

 side by side. 



It may be asked what is the reason for this constant 

 waste, which, with corresponding repair, is characteristic of 

 life ? The answer is a simple one, and brings us back to 

 the subject of the correlation of life with other forces. It 

 has 'been said before that all force must be the represen- 

 tative of the expenditure of force in another form. In the 

 case of the vegetable world, construction is the main object 

 to be attained, and the amount of light and heat expended 

 on the growth of plants is represented by the wood 

 formed. Inasmuch as the latter, when once deposited in 

 the act of growth, is not, for the most part, the seat of any 

 appreciable vital energy, so there is little or no change, 

 either in respect to waste or repair. New matter, more- 

 over, is deposited, chiefly layer by layer, almost as it might 

 be on a crystal. 



The structures of which animals are composed, on the 

 contrary, are placed under widely different conditions. 

 They are subject to constant wear and tear; from their 

 construction they are liable to incessant decay ; and 

 many are themselves the means of transforming physical 

 force into some form or other of vital energy. Thus there 

 is constant waste, and if the integrity of the body is to be 

 preserved there must be constant renewal. And as the 

 whole substance of living tissues, and not merely their 



