18 PHYSIOLOGY. 



its own proper substance, and builds it up into certain struc- 

 tures ; it also generates and maintains a certain degree of 

 temperature, and after having arrived at maturity decays 

 and dies ; but in addition to these vital processes which are 

 similar in both, the animal possesses the faculty of feeling 

 and moving spontaneously, or according to the dictates of 

 its will, a property peculiar to itself. 



21. Vegetables are nourished by the substances immedi- 

 ately around them, such as air, water, and the saline proper- 

 ties of the soil. They draw their support from without, by 

 absorption at their surface, or by means of roots. But 

 animals draw their nutriment from a great variety of sources, 

 and they are furnished with an internal cavity to receive 

 and prepare it for the purposes of nourishment. 



22. Vegetable matter is composed chiefly of three elements, 

 viz. carbon, hydrogen, and oxygen ; besides these, animal 

 matter contains azote, which gives the peculiar smell that we 

 perceive on burning flesh, hair, bones, or feathers. Eighteen 

 simple substances, however, have been found in vegetables, 

 in very small quantities ; such as lime, sulphur, iodine, silex, 

 potash, soda, &c. 



23. Animals and vegetables both consist of solid and fluid 

 parts ; the fluids, however, in animals, exist in much the 

 largest proportion. This is the reason why decomposition 

 occurs more rapidly in animals than in vegetables. Veget- 

 ables, abounding in fluids, decay sooner than those of a more 

 solid or fibrous texture. 



24. Though the differences between animals and veget- 

 ables, are in general sufficiently obvious and striking, yet 

 in some few instances, their distinguishing characteristics 

 are not so evident. This is apparent from the fact, that 

 some animals have been mistaken for vegetables, and some 

 vegetables for animals. Some animals we find to be as 

 firmly attached to the soil, as most vegetables are, as is the 

 case in many of the zoophytes, or lowest order of animals, 

 as the sponge, coral, &c. ; while on the other hand, some 



