THE BRAIN 



207 



and sensory areas which are concerned with sensations. Centers 

 of sensation, motor activities, speech, judgment, reasoning, mem- 

 ory, and many other activities requiring 

 thought are located in the cerebrum. Asso- 

 ciation units link these together and make 

 possible all kinds of connections. Later, in 

 considering the activity of the nervous sys- 

 tem, the cerebrum will be called the third 

 level. 



The cerebellum. Below the cerebrum and 

 partially covered by it lies a smaller por- 

 tion of the brain, the cerebellum. This 

 is the center of muscular coordination and 

 maintenance of body equilibrium. It may 

 be called the second level of the central nerv- 

 ous system. 



The medulla oblongata. The brain is 

 connected to the spinal cord by means of 

 the medulla oblongata. This is really the 

 enlarged beginning of the spinal cord but is 

 considered a part of the brain. It is the 

 crossing place for most of the impulses to 

 and from the nerves of the brain. It con- 

 tains the nerve centers which govern breath- 

 ing, regulate circulation, and maintain normal 

 tone of the muscles in the blood vessels. It , .... 



cerebrum and intelligence 



controls certain acts such as sneezing, swal- ^he lower down in the am 

 lowing, vomiting, and blinking. 



The spinal cord. The spinal cord, nearly 

 cylindrical in form, runs through the hollow vertebral column. 

 It is connected with the brain by the medulla oblongata. The 

 spinal cord serves as a pathway for nervous impulses from various 

 parts of the body to and from the brain, and has centers of simple 



pigeon 



ccct 



Note the relative size of 

 the cerebrum in each of the 

 brains. There is a close re- 

 lation between size of the 



mal scale, the smaller the 

 cerebrum and the lower the 

 intelligence. 



