466 THE NERVOUS SYSTEM. 



substance of the brain. It was denominated by Bichdt 

 the nervous system of animal life ; and includes all the 

 nervous organs in and through which are performed the 

 several functions with which the mind is more immediately 

 connected, namely, those relating to sensation and volition, 

 and the mental acts connected with sensible things. 



The sympathetic or ganglionic portion of the nervous 

 system, which Bichat named the nervous system of organic * 

 life, consists essentially of a chain of ganglia connected 

 by nervous cords, which extend from the cranium to the 

 pelvis, along each side of the vertebral column, and from 

 which, nerves with ganglia proceed to the viscera in the 

 thoracic, abdominal, and pelvic cavities. By its distribu- 

 tion, as well as by its peculiar mode of action, this system 

 is less immediately connected with the mind, either as 

 conducting sensations or the impulses of the will ; it is 

 more closely connected than the cerebro-spinal system is 

 with the processes of organic life. 



The differences, however, between these two systems, 

 are not essential: their actions differ in degree and object 

 more than in kind or mode. 



Elementary Structures of the Nervous System. 

 The organs of the nervous system or systems are com- 

 posed essentially of two kinds of structure, vesicular and 

 fibrous ; both of which appear essential to the construction 

 of even the simplest nervous system. The vesicular 



* The term organic is often used in connection with a function, 

 such as digestion or secretion, which belongs to all organised heings 

 alike ; while the term animal function, or animal life, is used in con- 

 nection with such qualities as volition or motion, which seem altogether 

 or in great part to helong only to animals. The terms which have been 

 thus used in this general way, are often loosely applied to special tissues. 

 Thus organic nerve-fibres are those which are distributed especially to 

 organs concerned in the discharge of the functions of organic, as distin- 

 guished from animal life ; and the term is still more commonly applied 

 to a kind of muscular fibre. 



