INTRODUCTION. 



the other ascending and surrounded by the atmosphere, is the 

 stem, body, or tree which bears the leaves and flowers. Their 

 structure consists, simply, in an areolar tissue, vessels and spi- 

 ral tubes, which are called tracheae. They possess no other 

 organs than those of nutrition and generation. Their most 

 important and vital parts are all situated externally. Their 

 chemical composition is rather simple; nitrogen is seldom met 

 with in them, and if found at all, it exists only in some par- 

 ticular part. Their vital action is confined to their growth 

 and reproduction. Their nutrition, the materials of which 

 are drawn from the earth and atmosphere, from water and air, 

 consists in an absorption induced by the roots, by a move- 

 ment of translation that the liquids experience in the vessels 

 of the stem, and in a kind of respiration which occurs prin- 

 cipally in the leaves: in these various actions vegetables re- 

 tain hydrogen and carbon, little or no nitrogen, and ex- 

 hale the superfluous oxygen. Their reproduction is induced 

 in divers manners. There is, moreover, in the organization 

 of vegetables, a very great diversity, which can not be pro- 

 perly treated of in this work. 



OF ANIMALS. 



11. Animals, at the head of which is man, who 

 closely resembles some of them, besides the general charac- 

 ters of organized bodies, have others which are peculiar to 

 themselves, which consequently distinguish them from vege- 

 tables, and which have an influence on, and modify the for- 

 mer. But animals are so very different from each other, that 

 their characters, which may be said to be common, are nei- 

 ther very numerous, nor very distinct. The following are 

 those peculiar to animals, some few of which are common to 

 all, and others are more or less general. 



Besides the rounded form which belongs generally to all 

 organized beings, we observe that the greater number of ani- 

 mals are, at least externally symmetrical and divided by a 

 median vertical line, into two lateral and similar halves, and 

 that their length in this direction, is greater than in any other 

 of their dimensions. The liquids greatly predominate over 



