386 THE NERVE SYSTEM 



The White Kami. These contain medullated nerve 

 fibers and have their origin in the ganglia of the cord; 

 and other axones also pass from the ganglia forward 

 by way of the rami to the spinal nerve, and terminate 

 through these nerves, to be distributed to the plexuses 

 in the abdominal and thoracic organs. 



The Gray Rami. These are composed of non- 

 medullated nerve fibers; the axones arise in the nerve 

 cells of the central ganglia and pass to the spinal 

 nerve, wherein they are conveyed to the structure 

 in the skin, non-striated muscles of bloodvessels and 

 the hair follicles, also the epithelial cells of the glands. 

 The foregoing description of the white and gray rami 

 show the course of the efferent nerves from the nerve- 

 cells situated in the lateral and anterior portion of 

 the gray matter in the thoracic and lumbar regions 

 of the spinal cord. The axones from these nerve cells 

 leave the spinal cord by way of the anterior root, 

 at the point where the anterior and posterior roots 

 join to form the common trunk of the spinal nerve, 

 to pass to the ganglion wherein the axones are in 

 relation with other neurones. 



The afferent sympathetic fibers give rise to pain 

 and other reflex phenomena when stimulated. They 

 reach the spinal centres by passing through the gray 

 rami to the ganglion on the posterior root, where 

 they communicate with other neurones and are con- 

 veyed by their axones to the cells in the posterior 

 horns of the spinal cord; some fibers pass into and 

 through the white rami. 



The Functions of the Sympathetic System. It is a 

 connecting link between the cerebrospinal system and 

 the tissues of the body which carry on the involun- 

 tary functions. By the connection of the ganglion 

 with each other, and the spinal cord and brain at 

 different levels, through the rami communicantes, 

 one can easily understand the numbers of different 

 routes by which impulses can pass, thus influencing 



