OF NATURAL HISTORY. ii 



rated from the body to which they belong, have no diftlnft per- 

 ception of pleafure or pain. Their regular contradion and dilata- 

 tion are evident fymptoms of life, which, in many cafes, may lead 

 us to attribute living powers to fubftances that enjoy neither life 

 nor fenfation. Hence, though all plants were irritable, this circum- 

 ftance would not prove that they are poflefTed of life. The con- 

 traftion and dilatation of the fenfitive plants, and the various mo- 

 tions of the leaves, branches, flowers, and roots of vegetables for- 

 merly mentioned, feem to indicate that moft plants are endowed 

 with irritability. Perhaps all vegetables have more or lefs of this 

 quality. The heart, inteftines, and diaphragm, are the moft irri- 

 table parts of animal bodies : And, to difcover whether this quality 

 refides in all plants, experiments fhould be made chiefly on their 

 leaves, flowers, buds, and the tender fibres of the roots. 



From this narration of fads, it appears, that plants make a very 

 near approach to animals ; and that this fimilarity, as well as the 

 difficulty of fixing the precife boundaries by which thefe two great 

 kingdoms of nature are limited, are diredt confequences of the or- 

 ganization of vegetables. It is owing to their organic ftrudure 

 alone, that plants and animals are capable of affording leciprocal 

 nourifhment to each other. This organic ftru£ture, though greatly 

 diverfified in the different fpecies of animals and vegetables, evinces 

 that Nature, in the formation of both, has aded upon the fame ge- 

 neral plan. May we not prefume, therefore, as plants as well as ani- 

 mals are compofed of a regular fyftem of organs, that the vegetable 

 part of the creation is not entirely deprived of every quality which 

 we are apt to think peculiar to animated beings ? I mean not to in- 

 fmuate, that plants can perceive pleafure or pain. But, as many of 

 their motions and affedlons cannot be explained upon any prin- 

 ciple of mechanifm, I am inclined to think, that they originate from 

 the power of irritability, which, though it implies not the percep- 



B. 2- tion- 



