THE STORY OF THE BRAIN AND NERVE 101 



CHAPTER VI 



THE STORY OF THE BRAIN AND NERVE 



THE Two NERVOUS SYSTEMS. The control of a 

 living body, like the government of a country, is 

 found to be determined by a specially appointed 

 organisation to which we apply the general name of 

 the nervous system. This system, whilst exhibiting 

 a distinct unity, is nevertheless composed of elements 

 or parts of diverse importance, some being of vastly 

 greater importance than others, judged by the special 

 share of the work of government they perform. 

 Two nervous systems exist in the bodies of all back- 

 boned animals, a fact already alluded to when we 

 dealt with the general constitution of the body. The 

 more important of these two systems consists of the 

 brain and spinal cord (Fig. 29 and 30), which last may 

 be described as the main line of the nervous system, 

 lying protected within the spine, and the nerves issu- 

 ing from both brain and cord supplying the body with 

 the means of communication between itself and the 

 outer world. The second system, known as the 

 sympathetic system, exists in the form of a double 

 chain of ganglia or masses of nerve cells lying in front 

 of the spine. This latter system has an individuality 

 of its own, though it is connected at certain points 

 with the brain system of nerves. The term cerebro- 

 spinal system is scientifically applied to the latter in 

 contra-distinction to the term sympathetic, denoting 

 the other main portion of the nervous apparatus. In 



