NERVOUS SYSTEM 387 



really the enlarged tipper portion of the spinal cord. 

 It forms a connection between the spinal cord and the 

 brain. 



The pons consists of broad bands of nerve tissue that 

 pass around the ventral side of the medulla and connect 

 the two halves of the cerebellum. 



Twelve pairs of nerves, called cranial nerves, arise 

 from the brain. These are distributed to different parts 

 of the head and to the body. 



Functions of brain. The functions of the parts of the 

 brain are as follows: 



The cerebrum is the seat of all sensations, of intelli- 

 gence, of memory, of emotions, and of will. Through 

 it we receive all sensations such as sight, touch, and 

 taste, and in it originate all impulses which produce 

 voluntary movements. 



The cerebellum does not start voluntary motion but 

 it coordinates these movements and makes them defi- 

 nite. If the cerebellum is removed from a pigeon, for 

 example, the pigeon can still move but it cannot walk 

 or fly. The various pairs of muscles do not work 

 together ; those of the right side do not work with 

 those of the left. Consequently the pigeon nutters 

 about, but it can make no definite movements. 



The medulla is a passageway for impulses between 

 the brain and the spinal cord. 



Spinal cord. The large nerve which passes down 

 through the backbone, or spinal column, is called the 

 spinal cord. It tapers somewhat at the lower end, but 



