CEREBELLUM AND THE SEMICIRCULAR CANALS 875 



canal could be compressed and currents set up in the endolymph. It was 

 found that these currents always caused the animal to move its head and 

 eyes in the plane of the canal that was being- stimulated and in the direction 

 of the current of endolymph. 



Finally, visual impressions supply much of the information the cerebel- 

 lum requires, the close association of the movements of the eyeballs with 

 cerebellar and labyrinthine disturbances being well recognized. The nys- 

 tagmus already described in connection with Barnay 's tests is dependent 

 upon this association. The symptoms and sensations of giddiness or nausea 

 produced by rotation of the body, or by unusual movements such as those 

 of a boat, are no doubt due to the irregular and unusual variety of laby- 

 rinthine sensations which they excite. 



In a word, then, the function of the cerebellum is to receive proprio- 

 ceptive impulses from the body along with labyrinthine and visual im- 

 pressions and to integrate and develop from them impulses which, by 

 being transmitted to the cerebral and other nerve centers that dominate 

 muscular movements, so coordinate the nerve discharges from them that, 

 when muscular movement occurs, it does so in relationship to the previous 

 position of the animal and in the most efficient way to attain the object 

 for which the movement was made. The cerebellum is the head nucleus 

 of the proprioceptive system. 



THE ASSOCIATION BETWEEN THE EYE MOVEMENTS AND THE 

 SEMICIRCULAR CANALS 



The close association between the eye movements and the semicircular 

 canals is indicated by the occurrence of nystagmus when the ear is stimu- 

 lated either electrically or by means of moderately cold water impinging 

 on the membrana tympani. The latter method of inducing nystagmus is 

 styled the caloric, and is employed in the examination of candidates for 

 the aviation service. Its value over the tests of nystagmus after rotating 

 the body and the index test already described depends on the fact 

 that it enables us to test each vestibular apparatus separately. 



Water at 68 F. is allowed to run through a stop nozzle into the ex- 

 ternal auditory canal, free of wax, from an irrigation bottle placed 

 about 3 feet above the head, which is meanwhile tilted at an angle of 30 

 forward. In about 40 seconds a rotary nystagmus with the direction of 

 the jerk to the side opposite to the douched ear should be evident, or 

 dizziness complained of. The reaction test is then applied and im- 

 mediately afterward the head is inclined at an angle of 60 backward 

 from the perpendicular, when a horizontal nystagmus to the side op- 

 posite to the douched ear should develop. Deviation is again tested. 



