THE BLOOD AND THE NERVES 



207 



The next time you have chicken for dinner, separate 

 the vertebraB of its neck, and notice 

 the pithy cord extending through the 

 center of these bones. It is the 

 chicken's main telegraph wire, or 

 spinal cord, which is very much like 

 ours in appearance, though, of course, D 

 smaller. 



The brain, the ganglia, and the spi- 

 nal cord with the thousands of nerves 

 extending from it, form what is com- 

 monly called the Nervous System. 

 When we see, hear, or smell any- 

 thing, the nerves of the eyes, ears, 

 or nose carry the information to the 

 brain. When a feeling of heat, cold, 

 pain, or any other sensation is re- 

 ceived, the brain is at once made 

 aware of the fact through the nerves 

 near the surface of the body. Nerves 

 accompany blood-vessels everywhere 

 in the body. They help control the 

 blood supply by telegraphing to the 

 brain the needs of the various parts, 

 and carrying back to the arterial 

 muscles the command to relax or 

 contract. 



Knowing how the brain controls The backbone or spinal 

 all the muscles and other organs, column side view, 



