32 ELEMENTARY PHYSIOLOGY. 



middle, shows us the right hemisphere of both the 

 larger and the smaller brain. The red vessels, in the 

 figure, are blood-vessels which bring large quantities 

 of the purest blood in the body to the brain, for a 

 purpose of which we shall learn hereafter. 



From many observations and experi- 

 ments which have been made by 

 physiologists, it has been learned 

 that the large brain is the thinking organ of the 

 mind. It is here that impressions received from 

 the outside world are translated into thought and 

 feeling. Here the purposes of the will are formed, 

 and from here all orders for the action of the volun- 

 tary muscles are issued. 



The work of the small brain seems to 



Work of the , . . , 



cerebellum " e to regulate the muscuJar movements 

 which are directed to be made by the 

 large brain. It has been discovered that when the 

 cerebellum is injured, a person can not balance 

 the body, as is required even in standing and much 

 more in walking. A bird whose small brain is 

 seriously injured or removed, can move its wings 

 and its legs, but it can neither fly nor walk. 



The nervous matter of the brain is con- 

 Cord. P " * tinned down through the back, passing 



through openings in the bones of the 

 spinal column. This is called the spinal cord. Here 

 (131, last section of the head) is where the spinal 

 cord begins. This (124) upper part of the cord 

 (medulla oblongata) is a very important part of the 



