2l6 THE NERVOUS SYSTEM 



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 sensation, 

 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 functions 

 similar to those occurring in the vegetable kingdom. It pre- 

 sides over all organic life over all unconscious activity. 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 inde- 

 pendent 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 elements known as neuroglia, which, 

 though not identical with connective tissue, is comparable to it 

 in its function of support. The neuron, thus considered, consists 

 of a protoplasmic body which sends out a number of branching 

 processes called dendrites, one of which becomes the axis cylinder. 

 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 



