126 ILLINOIS ACADEMY OF SCIENCE 



iilar stimulation but that, on tlie contrary, it is highly 

 variable in its appearance. Moreover, it is but one of a 

 large number of effects which contribute to that complex 

 experience known as dizzmess. 



As further evidence on the nature of nystagmus result- 

 ing from rotation we have instituted a series of experi- 

 ments in which subjects were started with a number of 

 revolutions so small that none of the usual effects was 

 obtained. We then gradually increased from day to day 

 the number of turnings. It will be observed that this 

 procedure is just the reverse of what has usually been 

 done, viz., starting subjects with as many as ten revolu- 

 tions in order to get rotational effects of optimal in- 

 tensity, and so to note the decrease in the intensity and 

 duration of these effects as practice continues. In our 

 new series, it was found possible finally to rotate a subject 

 as many as ten revolutions without, at any time, having 

 produced nystagmus or any of the other effects usually 

 found. That is to say, in our former experiments, the 

 number of turnings was kept constant from day to day, 

 the changes occurring in the duration and in the intensity 

 of the rotational effects. In our new series, the rotational 

 effects continually failed to appear and were thus in a 

 sense, as we shall see, constant, while the number of revo- 

 lutions was constantly increasing. 



In order to carry out these experiments six subjects, 

 underclassmen in the University of Illinois, were given 

 the usual clinical nystagmus and past-pointing tests for 

 '* normality". The Barany tests for "vestibular nor- 

 mality" mentioned above, have given the following sig- 

 nificance to the term "normal." It means that after ten 

 revolutions in twenty seconds, either to the right or to 

 the left, the after-nystagmus should last for about twenty- 

 five seconds. Furthermore, if, after ten revolutions, the 

 subject is asked to raise his arm quickly above his head 

 and then to lower it to a point he supposes to be directly 

 in front of him, he will usually 'past-point' either to the 

 right or to the left, according to the direction of rotation. 

 All of our subjects past-pointed "normally", that is, ap- 

 proximately three times. The after-nystagmus times, the 



