716 



Popular Science Monthly 



direction. And so it is that the flowing of the 

 endolymph within these canals acquaints us 

 with the direction of our head movements. 



Testing Ears to See If You 

 Can Fly 



Now since the testing of the 

 static labyrinth is obviously de- 

 pendent upon the movement of 

 the fluid or endolymph within 

 the canal, some 

 means must be em- 

 ployed for causing 

 the endolymph to 

 flow within the 

 canal. Hence, a 

 special kind of re- 

 volving chair is used 

 which is known as 

 the ."Jones' modifi- 

 cation of the Barany 

 chair." The appli- 

 cant is seated in the 

 chair and directed to 

 incline his head 

 thirty degrees for^ 

 ward. That brings 

 the horizontal canal 

 within the level 

 plane of turning. 

 With eyes closed, 

 the applicant is 

 whirled ten times in 

 twenty seconds in 

 this position. Then 

 the chair is stopped, 



and the applicant is told to look at a dis- 

 tant object. The visual, disturbance result- 

 ing from the experiment is known as the 

 nystagmus. The duration 

 of his nystagmus is noted 

 with a stop watch ; it should 

 last in a normal person 

 about twenty-six seconds. The nystagmus 

 may be described as a rhythmic to and fro 

 motion of the eyes, consisting of two move- 

 ments — a slow movement in one direction 

 which is followed at once by a rapid move- 

 ment in the opposite direction. This nystag- 

 mus lasts only so long as the fluid within the 

 canal tested continues to flow artificially. 



The applicant is now turned in the op- 

 posite direction and tested in like manner. 



Still seated in the revolving chair, un- 

 changed in position and with eyes closed, 

 the applicant is tested for "pass-pointing." 

 He extends his right arm and touches the 

 examiner's hand with his forefinger. From 

 this position he raises his arm to a vertical 



position and attempts to bring his finger 

 back and touch the examiner's hand again. 

 He is now turned ten times in ten seconds 

 to the left or right. The chair is stopped 

 and his hand is seized by the examiner. 

 He is told to raise his arm and come back 

 and touch the examiner's finger as before. He 

 cannot do it if his static labyrinth is normal. 

 The underlying 

 principle of the fore- 

 going test is not dif- 

 ficult to understand. 

 Since the applicant 

 was turned tp the 

 right, in this case, 

 and the chair 

 stopped, the fluid in 

 the horizontal canal 

 continued to move 

 to the right after the 

 chair was stopped — 

 continued to move, 

 in other words, in 

 the direction of turn- 

 ing. Hence, the 

 applicant feels that 

 he is being turned 

 to the left, and in 

 trying to locate the 

 finger of the exam- 

 iner, he naturally 

 pass-points to the 

 right. 



The Result of the Falling Test 



After having been turned five times in ten 

 seconds to the right or left, with eyes closed, 

 the applicant feels that he is falling to the right 

 when he sits up with his eyes closed. He tries 

 to overcome this and actually falls to the 



The Three Testing Positions 



The whirling tests are made with the applicant seated 

 with his head either at an angle of thirty degrees 

 forward or at ninety degrees. The position sixty 

 degrees backward is usually used for a douche or 

 caloric test when the whirling tests are unsatisfactory 



