CEREBRAL CORTEX AND VESTIBULAR NYSTAGMUS 



one examination. Struggling has a marked inhibitory effect 

 upon the duration and the number of movements of the after- 

 nystagmus. When the eye is turned in the direction of the quick 

 component, the nystagmus is increased, and vice versa, as is the 

 case in man. With these and other factors controlled, there 

 was a marked variation in two of the eight rabbits examined. 



Hemi-decerebration in the rabbit does not abolish the quick 

 component of nystagmus. It is present when the animal is 

 rotated in both directions, but there is a difference in intensity 



TABLE 2 

 Showing the effect of hemi-decerebration in the rabbit on vestibular nystagmus 



1 When the table was stopped, having rotated only a quarter of a turn, two to 

 three postrotatory movements invariably occurred. This never occurs in the 

 normal rabbit nor in the hemi-decerebrate when rotated to the left. 



2 Figures represent the number of quick movements when the rabbit was ro- 

 tated through an arc of 90° at a speed of one turn in two seconds. The postrota- 

 tory movements were elicited by rotating ten times at a speed of one turn in two 

 seconds. 



(table 1). The rotatory nystagmus is diminished, almost ab- 

 sent, when rotated opposite to the side of the lesion, but the post- 

 rotatory nystagmus is intensified. The rotatory nystagmus is 

 normal when rotated to the side of the lesion, the postrotatory 

 nystagmus being apparently somewhat diminished. Sometimes 

 a latent period of from two to five seconds occurs before the after- 

 nystagmus, which is liable to cause one to overlook the reaction 

 entirely. If the animal is depressed or manifests marked activ- 

 ity and restlessness, the quick component is irregular in its 

 occurrence or may be entirely absent. 



