110 THE NERVOUS TISSUE. 



form, the Brain, the analysis of which, according to Vau- 

 quelin, is 



Albumen, 



Cerebral fat, 



Phosphorus, 



Osmazome, 



Acids, Salts, Sulphur, 



Water, 



100.00 



The Nerves. The primitive fibres already spoken of, 

 collected in bundles and surrounded by a sheath, their 

 neurilemma, constitute a nerve. Nerves are of various kinds, 

 which the dissections and experiments of Sir Charles Bell 

 most clearly demonstrate. 



He distinguishes nerves of Motion, nerves of Sensation, 

 and Kespiratory nerves. Dr. Hall has since added, what 

 he calls, the Excito-Motor nerves. 



The nerves, composed of many filaments, have their 

 roots or origin in a line or streak of nervous matter, as 

 seen in the Brain, which is called a Tract. When these 

 streaks are raised, the term rod or column is applied, as 

 the anterior and posterior rods of the spinal marrow. 



These tracts and columns of nervous matter, are consid- 

 ered the sources of endowment to all the nerves originating 

 in them, and the different endowments and peculiar func- 

 tions of each are owing to the fact of their arising from 

 different nervous tracts. 



All nerves arising from the same tract, have the same 

 endowment their whole length, from origin to termi- 

 nation. For example, if we take a filament of a nerve 

 whose office is to convey sensation, that power will belong 

 to it in all its course, whether traced in the foot, leg, spine 

 or brain. When pricked or injured in any way, sensation, 

 and not motion, will be the result, and the perception of 

 the impression will be referred to that part of the skin 

 where the remote extremity of the filament is distributed. 



