ANIMALS AND VEGETABLES. 69 



mals and vegetables have but an ephemeral existence, some of the 

 more elevated individuals of the two kingdoms outlive a century. 



8. Motive forces i Lastly, observation has satisfactorily proved, that 

 there are certain forces, which affect matter in general, inorganic as 

 well as organized ; and that, in addition to these, organized bodies 

 possess a peculiar force or forces, which modify them in a remarkable 

 manner. Hence, we have general forces; and special or vital; the first 

 acting upon all matter, the dead and the living, and including the forces 

 of gravitation, cohesion, chemical affinity, &c. ; the latter appertaining 

 exclusively to living beings. 



Such are the chief distinctions to be drawn between the two great 

 divisions of natural bodies ; the inorganic and the organized. By the 

 comparison which has been instituted, the objects of physiology have 

 been indicated. To inquire into the mode in which a living being is 

 born, nourished, reproduced, and dies, is the legitimate object of the 

 science. We have, however, entered only into a comparison between 

 the inorganic and the organized. The two divisions constituting the 

 latter class differ also materially from each other. Into these differ- 

 ences we shall now inquire. 



2. DIFFERENCE BETWEEN ANIMALS AND VEGETABLES. 



The distinctions between the divisions of organized bodies are not so 

 rigidly fixed, or so readily appreciated, as those between the inorganic 

 and the organized. There are certain functions possessed by both ; 

 hence called vegetative, plastic, or organic, nutrition and reproduction, 

 for example ; but vegetables are endowed with these only. All organ- 

 ized bodies must have the power of assimilating foreign matters to their 

 own substance, and of producing a living being similar to themselves ; 

 otherwise, the species, having a limited duration, would perish. In 

 addition to these common functions, animals have sensation and volun- 

 tary motion ; by the possession of which they are said to be animated. 

 Hence, they are termed animals, and the condition is called animality. 

 This division of the functions into animal and organic has been adopted, 

 with more or less modification, by most physiologists. 



Between animals and vegetables, situate high in their respective 

 scales, no confusion can exist. The characters are obvious at sight. 

 No one can confound the horse with the oak ; the butterfly with the 

 potato. It is on the lower confines of the two kingdoms, that we are 

 liable to be deceived. Many of the zoophytes have alternately been 

 considered vegetable and animal ; but we are generally able to classify 

 any doubtful substance with accuracy; and the following are the prin- 

 cipal points of difference. 



1. Composition. It was long supposed, that the essential difference 

 between animal and vegetable substances consists in the former con- 

 taining nitrogen ; whilst the latter do not. Modern researches have, 

 however, satisfactorily shown, that the organized portions of animals 

 and vegetables are essentially alike ; and consist of the four elements, 

 carbon, oxygen, hydrogen, and nitrogen ; whilst the unorganized 

 as the fat of the animal, and the starch of the vegetable are composed 

 of three elements only carbon, oxygen, and hydrogen. Still, their 



