876 THE CENTRAL NERVOUS SYSTEM 



The procedure is repeated on the other ear. If it takes longer than 90 

 seconds for the nystagmus to appear, the vestibular apparatus of that 

 side is abnormal. Absence of the reaction deviation after the douching is 

 a certain sign of internal ear disease. 



It is undoubtedly essential that these tests should be most carefully 

 applied to all would-be aviators. They frequently reveal lesions of the 

 vestibular apparatus or the cerebellum in subjects who had thought 

 themselves perfectly normal, and who indeed may have boasted of their 

 powers of equilibrium because they imagined that freedom from seasick- 

 ness or failure to become dizzy in dancing indicated a high development 

 of this function. There can be no doubt that many aviators have gone to 

 their death because of impairment in the ear mechanism. When on ''terra 

 firma" the muscular sense and cutaneous sensations often make the 

 vestibular weakness of no consequence, but when deprived of these con- 

 tributory sensations and dependent on the ear-balance mechanism alone> 

 as in flying, any weakness becomes a serious menace. 



It is probable that the value of the turning and past pointing tests has 

 been overestimated in appraising the flying abilities of aviation can- 

 didates. Recent work of Gordon Holmes and others has emphasized the 

 necessity of considering many other tests along with those designed to 

 detect changes in the equilibration apparatus of the ear. It is most im- 

 portant also to remember that the tests vary from time to time according 

 to the general body condition. Many aviators with unusually good flying 

 records have failed to pass the turning tests and others who have passed 

 them without a slip have found themselves quite incapable of judging 

 their position in the air while flying. 



