342 THE NERVE SYSTEM 



In other words, the various nerve fibers, in forming 

 a plexus, maintains the same function which the 

 nerve possesses from its origin, as motor, sensor, or 

 sympathetic. 



Ganglia. Aside from the arrangement of neurones 

 or nerve cells in the cerebrospinal system, there is 

 another collection of these neurones into small groups, 

 connected with each other and the nerves of the 

 brain and spinal cord called ganglia. Some ganglia 

 are large enough to be seen by the naked eye, others 

 are so small that they can scarcely be detected, unless 

 examined by a lens or microscope. Ganglia compose 

 the sympathetic system. They contain nerve cells 

 with dendrites and axones, the greater number of 

 the latter being non-medullated, and are surrounded 

 by a connective-tissue capsule. 



Ganglia are found on the dorsal or posterior root 

 of the spinal cord, on the sensor root of the fifth nerve, 

 on the facial and auditory nerves; and on the vagus 

 and glossopharyngeal, along either side of the spinal 

 column, where they form the gangliated cord of 

 the sympathetic. Ganglia are receptive to impulses 

 from nerves and other ganglia, and have the prop- 

 erty of conducting impulses to other ganglia and 

 nerves. 



Classification of Nerves. Nerves are pathways of 

 communication between the brain and spinal cord, 

 and the structures throughout the body which are 

 dependent upon the nerve system for their develop- 

 ment, growth, repair, and actions, and they require 

 the stimuli from the brain to excite into physiologic 

 activity the cells of muscles, glands, skin, mucous 

 membranes, organs of the thorax, abdomen, etc. 



There are two sets of nerves concerned in all nerve 

 action or reflex. One which transmits impulses from 

 the brain and spinal cord to the structure whose 

 activities are to be increased or retarded; others 



