DISTINCTION BETWEEN ANIMALS AND VEGETABLES. 1 1 



6. The structure and form of vegetables afford also marks 

 of distinction. These are sufficiently familiar without any 

 particular explanation. It is true that there are some marine 

 productions, such as the sponges, coral, &.G., having the shape 

 and in some measure the appearance of plants, which are yet, 

 without doubt, of animal origin. But of these it is to be re- 

 marked, that they are not animals themselves, but the resi- 

 dence of animals ; they are substances produced by the labor 

 of myriads of little polypes, who pile them up in order to 

 serve for their covering and habitation; and although, when 

 thus produced, they have the external shape of vegetables, the 

 creatures themselves, which have produced them, do not bear 

 the smallest resemblance to plants. 



7. The chemical composition of vegetables also differs 

 from that of animals. The elements essential to vegetables 

 are three in number, oxygen, carbon, and hydrogen; and 

 from these three principally are formed all the different sub- 

 stances which we meet aVnong plants. But besides these, 

 animals require the presence of azote or nitrogen also, which 

 is necessary to their composition ; and from this, combined 

 with the others in different proportions, are formed all the 

 parts absolutely essential to animal existence. There are, it 

 is true, many other elements which are found in some parts 

 of plants or animals ; but these are all which are absolutely 

 essential to the composition of vegetable or animal substance. 

 Thus, in the bark of some plants, besides the three element.* 

 necessary to its formation, there will be found a portion of 

 silex or flint ; and in the bones of animals, in addition to the 

 four essential elements, lime is deposited in large quantities. 

 So that, although there must always be present at least these 

 necessary and specified elements in the composition of vege- 

 tables and animals, there is no limit, no principle which pre- 

 cludes the admission of others. 



In consequence of this difference in chemical composition, 

 and perhaps of the mode in which the elements are combined, 

 other differences of a particular character may be detected 

 between substances of a vegetable and those of an animal 

 origin ; differences which serve, in cases of doubt, to assist us 

 in deciding to which class any particular substance belongs. 

 Thus, in burning, substances of animal origin always exhale 

 a very peculiar odor, that of burnt wool, feathers, sponge, 

 &.C., an odor easily recognized and not readily forgotten. 

 Tliis will always serve to determine whether any particular 

 substance, which we examine, is derived from the vegetable 

 or animal kingdom. 



