2l6 THE NERVOUS SYSTEM 



of the cells, is the highest manifestation of vital energy. 

 The nervous structure is divided into two great systems: 



1. The Cerebro-spinal System consists of the brain, the 

 spinal cord and all the nerves which run off from these. This 

 system is especially concerned with the functions of relation, 

 or of animal life. It presides over general and special sen- 

 sation, over voluntary movements, over intellection, over all 

 conscious activity, and over all other functions which are 

 peculiar to the animal. It is by this system that we know 

 of and deal with the other great system. 



2. The Sympathetic, or Ganglionic System is especially 

 connected with the functions relating to nutrition func- 

 tions similar to those occurring in the vegetable kingdom. 

 It presides over all organic life over all unconscious ac- 

 tivity. While the operations over which this system holds 

 sway are quite different from those under the supervision 

 of the cerebro-spinal system, it must not be concluded that 

 the two are not anatomically and physiologically related. 

 Neither is independent of the other, as was once thought, but 

 both are parts of the same great apparatus. 



Divisions of the Nervous Substance as a Whole. The 

 nervous matter, irrespective of the two systems, may be 

 studied as consisting of two divisions. The first is made up 

 of cells; the second of tubes, or fibers. Although the tissue 

 may be thus divided into nerve cells and nerve fibers, the 

 present conception of the arrangement of the nervous 

 substance is that these two are only different parts of the 

 same element known as the neuron, supported by tissue ele- 

 ments known as neuroglia, which, though not identical with 

 connective tissue, is comparable to it in its function of sup- 

 port. The neuron, thus considered, consists of a proto- 

 plasmic body which sends out a number of branching pro- 

 cesses called dendrites, one of which becomes the axis cylin- 

 der. While, therefore, it is to be understood that the cell 

 and the fiber in the nervous system are both portions of an 

 identical whole, a description of them as separate parts is 



