316 COORDINATION AND SENSATION 



and teachers do wisely when they insist upon the formation 

 of right habits by the young. 



Functions of Divisions of the Nervous System. The 

 relationship between the different parts of the nervous 

 system is very close and one part does not work inde- 

 pendently of other parts. At the same time the general 

 work of the nervous system requires that its different 

 divisions serve different purposes : 



1. The peripheral divisions of the nervous system are 

 concerned in the transmission of impulses between the sur- 

 face of the body and the central system and between the 

 central system and the active tissues. The nerves are the 

 carriers of the impulses. The ganglia contain the cell- 

 bodies which serve as nutritive centers ; and, in the case of 

 the sympathetic ganglia, these cell-bodies are the places 

 where the fiber terminations of one neuron connect with, 

 and stimulate, other neurons. 



2. The gray matter in the spinal cord, bulb, pons, and 

 midbrain (through the cell-bodies, fiber terminations, and 

 short neurons which they contain) completes the reflex 

 action pathways between the surface of the body and the 

 voluntary muscles, and also between the surface of the 

 body and the organs of circulation and digestion. 



3. The white matter of the spinal cord, bulb, pons, and 

 midbrain (by means of the fibers of which they are largely 

 composed) forms connections with, and passes impulses be- 

 tween, the various parts of the central nervous system. 



4. The bulb, because of certain special reflex-action path- 

 ways completed through it, is the portion of the central 

 nervous system concerned in the control of respiration, cir- 

 culation, and the secretion of liquids. 



Work of the Sympathetic Ganglia and Nerves. The neurons which 

 form these ganglia aid in controlling the vital processes, especially di- 



