PAPERS ON PSYCHOLOGY AND PHYSIOLOGY 127 



number of eye-movements made, and the length of time 

 during which the subject perceives the visual field to be 

 in apparent movement were registered by means of a 

 kymograph and electric signal markers. The results ap- 

 pear in Table I. They interest us, however, not as an in- 

 dex of '^normality" (our whole discussion shows that 

 they cannot be so used without certain reservations) but 

 as indicating the extent of the organic and mental effects 

 to be overcome by practice in our experimental series. 



Average 25.0 38.8 25.0 23.8 38.0 23.8 



Each of our subjects was then rotated from day to day 

 in an improved form of the Barany rotation chair. On 

 the first and second day's trials each subject was given 

 but one revolution for each trial during a rotation period 

 consisting of ten trials. On the third day the subjects 

 were given two revolutions at each trial. From this 

 point on, the number of revolutions in a trial was in- 

 creased from time to time as the several subjects per- 

 mitted. For example, if it M-as found after two days 

 rotation periods of ten trials each and two revolutions 

 to a trial that a subject could then be revolved three times 

 without the appearance of nystagmus, he was given at the 

 next regular session ten trials of three revolutions each. 

 In this manner, the number of continuous turns was grad- 

 ually increased until the investigation was discontinued. 

 Extreme care was taken at all times to avoid passing to 

 a greater number of turnings when to do so would arouse 

 a perceptible quiver of the eye. On the other hand, be- 

 cause of uncontrollable changes in the organic conditions 

 of the subjects, and because of the fact that the progress 

 in the development of inhibitions against the appearance 

 of nystagmus was so closely pursued, it was not possible 



