CHAPTER THIRD. 



FUNCTIONS AND ORGANS OP ANIMAL LIFE. 



SECTION I. 



OF THE NERVOUS SYSTEM AND GENERAL SENSATION. 



59. LIFE, in animals, is manifested by two sorts of func- 

 tions, viz. : First, the peculiar functions of animal life, or 

 those of relation, which include the functions of sensation 

 and voluntary motion ; those which enable us to approach, 

 and perceive our fellow beings and the objects about us, and 

 to bring us into relation with them : Second, the functions 

 of vegetative life, which are nutrition and reproduction ; * 

 those indeed, which are essential to the maintenance and 

 perpetuation of life. 



60. The two distinguishing characteristics of animals, 

 namely, motion and sensation (57), depend upon a special 

 apparatus, which is wanting in plants, and which is called 

 the nervous system. The nervous system, therefore, is the 



* This distinction is the more important, inasmuch as the organs of 

 animal life, and those of vegetative life, spring from very distinct layers of 

 the embryonic membrane. The first are developed from the upper layer, 

 and the second from the lower layer of the germ of the animal. Sec 

 Chapter on Embryology, p. 112. 



