HO 1)1 1 A HOTATIO.X 



527 



pearance of the nystagmus was directly proportional to 

 the number of rotations and to the speed of rotation. 

 For experimental purposes, an arbitrary choice was made 

 of a speed of ten revolutions in fifteen seconds. Ten 

 trials of ten rotations each were repeated two or three 

 times a day, save for subjects- " I" and ''J," which were 

 given twenty trials twice a day. The subjects were ten 

 white rats, five males and five females, all about three 

 months old. The functional integrity of the mechanisms 

 of equilibrium 7 was roughly determined by observing the 

 rats' behavior under daily conditions of life, and by 

 throwing them into the air and dropping them. All of 

 the subjects responded quickly and positively to such 

 tests. In the subsequent experiments each rat was ro- 

 tated a like number of times to the right and to the left, 

 and averages of the duration (in seconds) of the nystag- 

 mus after stopping were computed. A comparison of 

 these averages from day to day may be made from 

 Table I. 



The outstanding feature of the investigation is the 

 rapid decrease of after-nystagmus from day to day, as is 

 clearly indicated in Table I. Within ten to eighteen 

 periods of rotation the nystagmus had completely disap- 



the platform was also observed. Upon the first ^ota^ 

 tion for each rat, the number of movements varied be- 

 tween 18 and 25. This number rapidly decreased during 

 the first four or five periods to between 5 and 8, and soon 

 became reduced to a single movement which generally 



