BOOK VI 

 APPARATUS OF INNERVATIOJT. 



FIKST SECTION. 



THE NERVOUS SYSTEM IN GENERAL. 



THE functions whose instruments we have just described, suffice in them- 

 selves to maintain nutrition that mysterious molecular movement which is the 

 ultimate object of the activity of organs, and the essence even of life : loco- 

 motory acts which permit the animal to seek its food and to introduce it into 

 its organism, lead to 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 : in 

 brief, could anything more be required to constitute the conditions necessary 

 for the manifestation of the nutritive phenomena ? 



And yet, while the anatomist conceives in his mind a vertebrate animal 

 exclusively endowed with the apparatus destined to execute these functions ; 

 while he supposes the breath of life and the dependent properties of that 

 animating principle to be due to these apparatus, he could not succeed in 

 creating an imaginary being capable of moving, digesting, keeping in circula- 

 tion the nutritive fluids, reviving these fluids by respiration and urinary depu- 

 ration in a word, of executing all those acts whose concurrence is indispens- 

 able to the maintenance of nutrition, the supreme vital act. It is because the 

 tissues of that animal, though possessing the organic properties inherent in 

 their structure, require an excitant capable of bringing these properties into 

 play. Their inertia is due to the absence of this excitant ; for all motion, 

 no matter what kind it may be, demands for its realisation, not only the 

 motor faculty in the organ which executes it, but also an excitatory cause. 



But give to this mutilated organism, this creation of our fancy, white 

 cords, ramifying by extremely slender divisions in the depth of these 

 instruments of life, and commencing from a central axis lodged in the 

 cranium and spinal canal ; or, in other words, add to our incomplete 

 animal an apparatus of innervation, and, as if by enchantment, there will 

 appear the first signs of life. Owing to the peculiar properties which dis- 

 tinguish the tissues of this apparatus, and concerning which we will have 

 more to say hereafter, it plays the part of an excitor and regulator with regard 

 to the properties of the other tissues. Stimulated by the nervous system, these 

 properties no longer remain in a latent state, but manifest themselves by 

 their usual results such as contraction in the muscles, and exhalation 

 and secretion in the membranes and glands ; then the imperfect being at 

 once begins to digest, respire, etc. in a word, to live, and is worthy of 

 taking rank in the animated world. 



