FUNCTIONS OP THE CEREBELLUM 



871 



and (2) after producing artificial nystagmus. The artificial nystagmus is 

 produced by spinning the patient two or three times, and consists of con- 

 stant lateral movements of the eyeballs, quick in the direction in which the 

 artificial movement took place, and slow in the opposite direction. 



In a normal subject, previous to spinning the index test shows no devia- 

 tion, but after the production of artificial nystagmus a deviation is noted 

 in the direction corresponding to the slow jerk of the nystagmus (reaction 



Fig. 225. 



Fig. 226. 



Figs. 225 and 226 represent respectively the inferolateral and the posterior aspect of the human 

 cerebellum indicating certain cerebellar localizations according to Barany. (After Barany, from 

 Andre'-Thomas et Durupt. Op. cit.) N. VII, Nervus facialis; N. IX, Nervus Glossopharyngeus; 

 N. XII, Nervus hypoglossus. 



The signs in the above diagram indicate the exact localization of the centers for the tonus of 

 the musculature concerned in some of the movements of the right arm and leg, (g) marks the 

 center for downward movements of the arm; X, for abduction of the arm; O, adduction of the 

 hand; + adduction of the arm; , adduction of the hip. N. V. indicates Nervus trigeminus; 

 N. VI, Nervus abducens; N. VII, Nervus facialis; N. IX, Nervus glossopharyngeus; N. XII, 

 Nervus hypoglossus. (From Davidson Black.) 



deviation). When a cerebellar lesion exists, the index test performed on 

 a patient without nystagmus sometimes causes a spontaneous deviation in 

 the segment of the body corresponding to the position of the lesion on the 

 cerebellar cortex, but more frequently, if it is applied after the production 



