BOOK IX. 



PART I. 



Of the General Anatomy of the Nervom System. 



NERVOUS SYSTEM. 



THE Essential ingredient of this System is a peculiar animal 

 matter called Neurine, the texture of which is so soft, that in 

 the natural state it has the least possible consistence. It is, 

 therefore, protected in a variety of ways ; by being enclosed in 

 bone where it is collected in large masses, and by being sur- 

 rounded by ligamentous matter where flexure is required. 



The nervous system in man, and other vertebrated animals, 

 consists in two portions of dissimilar forms; one is spheroidal, 

 elongated at its base into a cylindrical process, and is contained 

 in the cranium and in the spinal canal; the other is an assem- 

 blage of arborescent rays, which proceed from different points 

 of the first portion, to every part of the body. The first por- 

 tion is the Central or Internal part of the nervous system, com- 

 posed of the Brain and Spinal Marrow, while the radiating 

 portion is called the External or Peripheral, and consists in the 

 Nerves of the brain and spinal marrow. 



The nervous system is remarkable for its symmetry; as it is 

 universally double, it very seldom happens that any striking dif- 

 ference of it on the two sides of the body is manifested, parti- 

 cularly as regards its Central portion; it is said, however, that 

 aberrations, in this respect, are more common in man than in 

 other mammiferous animals. 



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