368 THE NERVOUS SYSTEM. 



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 1 life, con- 

 sists 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, abdomi- 

 nal, and pelvic cavities. By its distribution, as well as by its 

 peculiar mode of action, this system is less immediately con- 

 nected 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 composed 

 essentially of two kinds of structure, vesicular and fibrous ; 

 both of which appear esssential to the construction of even the 

 simplest nervous system. The vesicular structure is usually 

 collected in masses, and mingled with the fibrous structure, as 

 in the brain, spinal cord, and the several ganglia ; and these 

 masses constitute what are termed nerve-centres, being the 

 organs in which it is supposed that nervous force may be gen- 

 erated, and in which are accomplished all the various reflec- 

 tions and other modes of disposing of impressions when they are 

 not simply conducted along nerve-fibres. The fibrous nerve- 

 substance, besides entering into the composition of the nervous 

 centres, forms alone the nerves, or cords of communication, 

 which connect the various nervous centres, and are distributed 

 in the several parts of the body, for the purpose of conveying 

 nervous force to them, or of transmitting to the nervous cen- 

 tres the impressions made by stimuli. 



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

 such as digestion or secretion, which belongs to all organized beings 

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

 nection with such qualities as volition or motion, which seem alto- 

 gether or in great part to belong 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 dis- 

 tributed especially to organs concerned in the discharge of the func- 

 tions of organic, as distinguished from animal life ; and the term is 

 still more commonly applied to one kind of muscular fibre. 



