THE NERVOUS SYSTEM 171 



Removal of this portion of the brain does not interfere with 

 eating or sleeping, but the animal cannot associate its sensations. 

 There are certain areas which can be mapped out on the cerebrum 

 of the dog for movements of the eye, the vocal cords, and move- 

 ments in response to commands. The human brain has been 

 mapped out in great detail, with results which show that the 

 intricacies of it are almost beyond conception. 



The function of the cerebellum is to act as the center for nerves 

 of coordination, for example, those in the semicircular canals 

 of the ears, the muscles, the tendons, and the joints, all of which 

 are concerned with movements and postures of the body. When 

 its physiologic activities are interfered with the animal reels when 

 it moves and acts as if intoxicated. A serious injury to the 

 cerebellum may cause the patient to walk or spin around in a 

 circle or turn somersaults. Coordination is the combination of 

 work of different muscles in orderly, harmonious action. It is 

 dependent upon the sending out of impulses over the dendrites 

 of afferent nerves to those of efferent nerves. The latter control 

 muscles whose actions are necessary to adjust the movement as 

 a whole. 



The functions of the pons and medulla are closely related and 

 play a most important part in the economy of the body. These 

 organs are remarkable for the great number of reflex centers they 

 contain — centers for the heart movements, respiration, swallowing 

 vomiting, for closure of the eyelids, and for other actions are 

 located in these portions of the brain. Pithing to destroy life 

 is performed by mutilating this part of the nervous system. 

 The medulla also acts as a great conductor of impulses to and 

 from the higher parts of the brain and the spinal cord. 



The functions of the spinal cord and spinal nerves are varied. 

 With the exception of a part of the face all of the body is endowed 

 with sensory nerve-fibers from the spinal cord. The nerve- 

 fibers of the ascending and descending tracts in both the white 

 and gray matter of the cord conduct sensations to and from the 

 brain, and, in conjunction with the spinal nerves, from one part 

 of the body to other parts. This latter function is dependent 

 upon the reflex centers which are located at different points in 

 the spinal cord. In the lumbar region there are special reflex 

 centers for impulses from the bladder, rectum, and the sexual 

 organs. The functions may be demonstrated by removing the 



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