GENERAL CHARACTERS OF ANIMALS. 7 



beings. Animals perceive, reflect, act spontaneously or by 

 their own will ; nothing of the kind, properly speaking, 

 exists in plants. Thus vegetables neither i'eel nor move; 

 animals feel and move. Differences also exist in the manner 

 in which the same functions are carried on in the two classes 

 of beings ; these remain with more propriety to be considered 

 afterwards. 



16. The faculties of animals being more complex than 

 those of plants, necessitate a greater complexity of organs. 

 These organs differ also in their intimate structure ; the tissues 

 in the vegetable affect a cellular or utriculose character, cells 

 provided with proper walls and cavities ; in animals, the tissues 

 are composed of little plates or laminae, which intersect each 

 other in such a way as to circumscribe imperfect lacunae, 

 and thus to constitute masses or membranes, more or less 

 spongy, but not divided into a number of utricules or cells, 

 independent of each other, as in vegetables. Often, it is true, 

 the animal tissue whilst being developed is seen to be com- 

 posed of little bags (utricules) ; but this structure, which is 

 permanent in plants, is generally but transitory in animals, 

 and is persistent only in a small number of organs, as, for 

 example, in the glands and epidermic membranes. 



17. Finally, the organized matters which form the basis 

 of plants are composed of carbon, hydrogen, and ox} r gen only. 

 To these in animals nitrogen is added. Allowing, however, 

 that there exists in plants azotized matters, and in animals 

 compounds which are not azotized ; still the organized matters 

 essential to the constitution of the living organs, offer in the 

 two kingdoms the chemical composition we have just in- 

 dicated. 



OF THE ORGANIC TISSUES OF ANIMALS, AND OF 

 THEIR ORGANS. 



18. Different elementary substances, but chiefly carbon, 

 hydrogen, oxygen, nitrogen, combine to produce the materials 

 of which animal bodies are composed. Amongst these materials 

 or matters, some are called organized or plastic, and form 

 the essential basis of all the solid parts animated by the vital 

 movement. These plastic materials are less varied than might 

 be at first supposed ; for in all animals the basis (frame) of 

 the living parts appears to be composed of a substance called 

 albumen, or of 'fibrin which probably is but albumen slightly 



