CHAPTEK IV. 



WASTE AND REPAIR. 



§ 62. Throughout the vegetal kingdom, the processes of 

 Waste and Eepair are comparatively insignificant in their 

 amounts. Though all parts of plants save the leaves, or 

 other parts which are green, give out carbonic acid; yet this 

 carbonic acid, assuming it to indicate consumption of tissue, 

 or rather of the protoplasm contained in the 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 func- 

 tional activity. Nor, indeed, is there displayed by plants in 

 any considerable 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 

 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 

 Eepair 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 removed from vegetal life. Actiniae 

 kept in an aquarium, do not appreciably diminish in bulk 



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