BOOK YI. 



APPARATUS OF INNERVATION. 



FIRST SECTION. 



THE NERVOUS SYSTEM IN GENERAL. 



The functions of the instruments which we have just described, suffice in them- 

 selves to maintain nutrition — the locomotory acts which permit the animal to 

 seek its food and to introduce it into its organism, the elaboration and absorption 

 of the assimilable materials of the alimentary mass in the interior of the digestive 

 cavity, the circulation of the reparative fluids in the economy, and the depuration 

 and revivification of these fluids by the action of the lungs and the kidneys ; 

 so that nothing more is required to constitute the conditions necessary for the 

 manifestation of the nutritive phenomena. 



Besides the apparatus necessary to carry on the functions of nutrition, how- 

 ever, there is needed an excitory system which will move them from their inertia, 

 and a regulating system to direct their special activity. These two systems are 

 found in the apparatus of innervation. Stimulated by the nervous system, the 

 properties of the apparatuses of nutrition no longer remain in a latent state, 

 but manifest themselves by their usual results. 



Thanks to the nervous system, the animal acquires all the attributes of what 

 it has become habitual, after Bichat, to term animal life — that is, sensibility, 

 volition, instinct, and intelligence. 



The perceptive centre which receives the stimuli developed at the periphery 

 of organs, or in their substance ; the excitatory centre which induces motion in 

 all the other tissues ; the seat of the instinctive and intellectual faculties, charged 

 with numerous and important functions — the apparatus of innervation presents 

 itself as a most attractive study. We will commence by giving a general and 

 succinct idea of its conformation, structure, properties, and functions, before 

 undertaking the special description of the different parts composing it. 



General Conformation of the Nervous System. 



The apparatus of innervation comprises a central and a peripheral portion. 



The first represents a very elongated mass lodged in the spinal canal, and 

 expanded at its anterior extremity, which occupies the cranial cavity. This is 

 named the cerebrospinal axis or centre. 



The second consists of a double series of ramescent branches, which are given 

 off laterally from the central mass, to be distributed to all parts of the body ; 

 these branches are the nerves. 



The Cerebko-Spinal Axis. — The axis, properly so called, lodged in the 



