PERSONAL APPEARANCES IN HEALTH AND DISEASE. 83 



walls of the arteries are not under voluntary control. 

 The nerves which go to them do not pass directly from 

 the brain or spinal cord, but are connected with a part of 

 the nervous system, which, although in part dependent on 

 the cerebro-spinal, is distinct enough, both in its arrange- 

 ment and structure, as well as in its functions. This is 

 the system of organic nerves, or, as it is also called, the 

 sympathetic system, and it consists essentially in collec- 

 tions of nervous cells called ganglia, connected by 

 bundles of nerve fibres down each side of the spine, 

 and from which proceed other nerves to the involuntary 

 muscles all over the body ; to the muscle of the heart, to 

 those of the intestines and stomach, &c., the movements 

 of all of which are not under voluntary control, but are 

 essential to the performance of the function of these organs. 

 The nervous system is then in its central parts duplex ; 

 there is the brain and spinal cord from which nerves 

 of voluntary motion and sensation arise, and there is the 

 sympathetic system from which nerves of organic life, 

 of involuntary movement arise. Going back to our illus- 

 tration, we find that the arteries of the body are kept in a 

 state of contraction by the sympathetic nerves. It has 

 been shown that when the sympathetic nerve in the neck 

 of a rabbit is paralysed, the ear on that side becomes red 

 and hot, and increases in size. There is in fact an in- 

 creased flow of blood to it, and this flow is due to greater 



