38 PHYSIOLOGY. 



READING. Power through Repose, Call ; The Technique 

 of Rest, Brackett ; Muscles and Nerves, Rosenthal. 



Summary. I . Motions are voluntary or involuntary, but all are 

 under control of the nervous system. 



2. The cerebro-spinal nervous system consists of the brain, the 

 spinal cord, and the spinal nerves. 



3. Each spinal nerve has two roots: the dorsal, which is afferent 

 and sensory ; the ventral, which is efferent and motor. 



4. A ganglion is a nerve center largely composed of nerve cells. 



5. Nerves are made up of nerve fibers. 



6. A nerve fiber consists of the central core (or axis cylinder), 

 which conducts the nerve impulse, the medullary sheath, and, outside, 

 the nerve-fiber sheath. 



7. The spinal cord has in its outer part white nerve fibers, in its 

 center gray nerve cells. 



8. These cells are branched, and at least one branch becomes the 

 axis cylinder of a nerve fiber. 



9. The gray matter of the cord is the center of the reflex action. 



10. The nerve fibers from each half of the brain connect with the 

 opposite half of the body. 



1 1 . The nervous system is comparable to a telegraph system. 



Questions. I. Name as many involuntary motions as you know. 



2. What other cases of reflex action do you know ? 



3. The story is told of a young Roman (Mucius Scaevola) that to 

 show his fortitude he thrust his hand into the fire and held it there 

 until it was destroyed. What physiological action does this illustrate ? 

 \j 4. Why is a man partially paralyzed when he has broken his neck 

 or back? 



5. How does the nervous system differ from a telegraph system? 



