xvi THE NERVOUS SYSTEM 237 



While we do not know just how the mind and the 

 brain are related, we do know that a strong, sound, and 

 vigorous mind demands a trained, healthy, and well- 

 nourished brain and body. 



SUMMARY OF THE MAIN POINTS 



1. The nervous system controls, regulates, and brings into 

 harmonious relation all the cells, tissues, organs, and systems 

 of the human body. 



2. The nervous system consists of nerves and nerve centers. 

 There are nerves from every cell in the body going to the 

 brain, and from the brain to all the muscles and glands. 



3. A nerve cell consists of a cell body with a large nucleus, 

 a main projection, the axone, and a number of treelike pro- 

 longations called dendrites. They vary much in size and 

 shape. 



4. The dendrites carry messages to the cell body, and the 

 axone away from the cell body. 



5. A nerve consists of a large number of nerve fibers bound 

 together with connective tissue and fat into a single trunk. 

 Each fiber is either an axone or a dendrite of some nerve cell. 



6. As to origin, we divide nerves into spinal and cranial, and 

 as to function, into sensory, motor, and mixed. 



7. The white matter of the cord forms pathways for the 

 ingoing impressions and the outgoing impulses, and the gray 

 matter, the central portion, consists of nerve centers for many 

 of the lower reflex acts. 



8. The brain is the central organ of the nervous system, and 

 consists of the bulb, the pons, the cerebellum, and the cere- 

 brum. It weighs about fifty ounces in man, and has a very 

 rough or furrowed surface. 



9. In the bulb at the upper end of the spinal cord, most of 

 the nerve fibers cross to the opposite side. The gray matter 



