THE SPINAL CORD 28 1 



cells from sending the order to cough. In the same way 

 men sometimes endure great pain without shrinking. 



508. Broken back. Injuries to the backbone may 

 injure the spinal cord so that it cannot conduct nervous 

 influences past the injured point. Then parts of the body 

 below the point of injury can neither send nor receive 

 messages from the brain, but are paralyzed both in sensa- 

 tion and motion. Yet the reflex action of the part may 

 persist, for the part of the cord below the injury still 

 retains its vitality. 



509. Disease of the spinal cord. There are diseases 

 which may destroy the action of any single part of the 

 cord or of the whole cord below the seat of the disease. 

 Then there will oe loss of sensation or of motion or 

 impairment of nutrition, usually in the lower part of the 

 body. The diseases are generally slow in their course and 

 incurable. 



510. The action of the cord is unconscious. The cord 

 always acts wholly without a person's knowledge. Like a faithful 

 nurse, it stands guard over the cells of the body and controls them in 

 their nutrition, growth, and work. The brain restrains its excessive 

 action and directs it in ordering the voluntary movements, but leaves 

 to it almost the entire care of individual cells. 



SUMMARY 



1. The spinal cord is made up of a central mass of gray 



matter surrounded by white matter. 



2. The gray matter is made up of cells from which nerve 



fibers extend both to the brain and to the cells of the 

 body. 



3. The white matter is composed of nerve threads which 



connect the cells of the cord with the brain and with 

 the nerves of the body. 



