CHAPTER IV. 



WASTE AND EEPAIE. 



§ 62. Throughout the vegetal kingdom, the processes of 

 Waste and Repair are comparatively insignificant in their 

 amounts. Though plants, and especially certain parts of 

 them, do, in the absence of light or under particular con- 

 ditions, give out carbonic acid; yet this carbonic acid, 

 assuming it to indicate consumption of tissue, indicates but a 

 small consumption. Of course if there is little waste, there 

 can be but little repair — that is, little of the interstitial repair 

 which restores the integrity of parts worn by functional acti- 

 vity. Nor, indeed, is there displayed by plants in any con- 

 siderable degree, if at all, that other species of repair which 

 consists in the restoration of lost or injured organs. Torn 

 leaves and the shoots that are shortened by the pruner, do 

 not reproduce their missing parts ; and though when the 

 branch of a tree is cut off close to the trunk, the place is in 

 the course of years covered over, it is not by any reparative 

 action in the wounded surface, but by the lateral growth of 

 the adjacent bark. Hence, without saying that Waste and 

 Repair do not go on at all in plants, we may fitly pass them 

 over as of no importance. 



There are but slight indications of waste in those lower 

 orders of animals which, by their comparative inactivity, 

 show themselves least remoyed from vegetal life. Actinias 

 kept in an aquarium, do not appreciably diminish in bulk 



