OP THE NERVOUS SYSTEM. 



CHAPTER X. 



OF THE NERVOUS SYSTEM. 



735. The Nervous System, Systema nerveum, compre- 

 hends cords (nerves,) enlargements (ganglia,) and a central 

 mass (the brain in general,) formed of a white and grayish 

 substance, which, during life, keeps up the irritability, are the 

 conductors and receptacle of the sensations, the point of de- 

 parture and the conductors of volition; in a word, the organs 

 of innervation. 



The nervous centre is moreover the organ, or in other words 

 the material instrument of intellect. 



736. The Asclepiades were not acquainted with either the 

 nerves or the ganglia. One may easily be convinced, on read- 

 ing the works of Hippocrates and Aristotle, that they have 

 confounded under the nameN^w, ligaments, tendons, nerves, 

 and even the vessels. Praxagoras appears to have been the 

 first who had any correct idea of difference among the white 

 organs; but having placed the origin of the nerves at the ter- 

 mination of the arteries, he gave rise to an opinion respecting 

 the hollow structure of the nerves, which has been continued 

 up to the present time. Herophilus and Erasistratus knew 

 the connexion of the nerves with the brain, but they continu- 

 ed to give the same name to the tendons and ligaments. Ga- 

 len unraveled the confusion which still prevailed in his time 

 with regard to this subject, by giving names to the ligaments 

 and tendons. By perceiving that the nerves are medullary in 

 their interior, and membranous at the exterior, he clearly de- 

 termined their connection with the spinal marrow and brain. 

 He remarked, in opposition to an opinion that had existed pre- 

 viously to him, that the spinal marrow is subordinate to the 



