THE BRAIN 119 



curious ocular reaction called nystagmus. It will be worth 

 while.to say a word about this movement. 



If a person is spun around, as in an office chair, the 

 eyes behave in a characteristic fashion. Suppose the 

 rotation is toward the left. The eyes fix themselves 

 upon some object and as the body is turned away from 

 it they are swung in the opposite direction (toward the 

 right), keeping the landmark in view as long as possible. 

 When the eyes can be carried no farther they are snapped 

 very sharply to the left and another object is seized upon. 

 There is again the measured sweep to the right and the 

 quick snap to the left. The name nystagmus is applied 

 to this alternating movement of the eyes in which the 

 travel opposite in direction to the rotation of the body is 

 moderate in speed while the counter-movement is ex- 

 tremely rapid. The behavior of the eyes may be likened 

 to that of the stop-watch, the hand of which moves from 

 its starting-point at a rate which is easily followed, but 

 eludes observation as it flashes back. 



When the subject of such an experiment is brought 

 to rest, the nystagmus continues for a time. . It is 

 accompanied by the distressing illusion that " every- 

 thing is going round and round." The uncontrollable 

 movements of the eyes continually shift the images upon 

 the retinas. It is thought that the quick, snapping 

 motions are not sources of sensation while the slower 

 ones are vividly effective. The result is, accordingly, 

 the impression that the surroundings are revolving in 

 one direction rather than oscillating back and forth. 

 By closing the eyes one lessens but does not entirely 

 do away with the feeling. When the shifting images can 

 no longer be seen there are still sensations from the eye 

 muscles as they go on with their unprofitable working. 



We are not justified in saying that the cerebellum is 

 the only central station through which the reflexes mak- 

 ing for equilibrium are brought about. Nevertheless, 

 it is the most obvious of such stations and it is un- 

 doubtedly traversed constantly by impulses which have 



