PAPERS OX PSYCHOLOGY AND PHYSIOLOGY 131 



The after-nystagmus was not the only effect of rotation 

 that was altered by practice. None of the subjects ex- 

 jDerienced vertigo at any time. On a few occasions a very 

 slight dizziness was reported; but in most of the cases 

 this was demonstrated to be coincident with the organic 

 disturbances from other causes. Xone of our subjects 

 past-pointed at the end of the investigation. That the 

 muscular effects of rotation usually leading to past- 

 pointing had dropped out was demonstrated in the fol- 

 lowing manner. A writing surface was placed in such 

 a position that a subject holding a pencil lightly in his 

 fingers could leave a record of the involuntary movements 

 of his arm. Automatographic records of this kind taken 

 before practice show a marked deviation either to the 

 right or to the left depending upon the direction of rota- 

 tion. In this case, however, there was no larger devia- 

 tion than is usually o^'iiig to inertia. - 



That this increasing ability to be rotated without the 

 appearance of nj'stagmus is not a matter of fatigue is 

 suggested, first of all, by the fact that 24 hours elapsed 

 between successive rotation periods. In the second place, 

 subject E was rotated at intervals of from two to three 

 days with the same results as the other subjects. Fin- 

 ally, all of the subjects were rotated again from four to 

 six weeks after the regular series had ended. From 

 Table IV, which summarizes these trials, it appears that, 

 in general, the loss of the effect of practice is negligible, 

 subjects C and F showing no nystagTiius after ten revo- 

 lutions and the other subjects showing but a fraction of 

 the original values. Subject A presents an apparant ex- 

 ception to this generalization. By refering to Table I, 

 however, it ^^ill be seen that A's original values were un- 

 usually high. Furthermore, enough evidence has been 

 collected to show that the appearance of after-nystagmus 

 is largely dependent upon the conditions under which 

 rotation is done. These conditions are both physical and 

 mental and they are not always obvious to the experi- 



* For a fuller description of this method and for more complete results 

 in other experiments see Griffith, C. R. J. of Exper. Psychol. 1920, 3, 36-37. 



