BOOK V7. 



OF INNERVATION. 

 CHAPTER I. 



THE NERVOUS SYSTEM IN THE ZOOLOGICAL SERIES. 



WE have now arrived at the most elevated point of elementary 

 differentiation of organised matter, and at the most aristocratic 

 properties of that matter. Every living substance is nourished. 

 Certain histological elements are nourished, move and contract 

 themselves. Certain others, the elements of the nervous tissue, 

 posses*, besides the fundamental property of nutrition, a 

 whole group of special properties. Thus, the nervous cells 

 can excite the contraction of the muscular elements ; they 

 have motricity. Moreover they have the consciousness of the 

 action exercised on them by the ambient mediums ; they feel 

 pain and pleasure. They can also, by means of the organs of 

 the senses, classify, select the excitations bearing on the extremi- 

 ties of the nervous fibres, with which they are anatomically 

 related. They have sensibility. Finally, they can treasure up, 

 combine in a thousand manners the sensations perceived ; 

 they can think and will. It is the totality of these primordial 

 properties which constitutes innervati.on. 



As we see, innervation is a very complex whole. Also the 

 anatomical tissue which is endowed therewith, and the systems 



