624 



Spontaneous eye-moveinents maj come into play here. Sometimes we 

 fancied to note an increased frequency when the animal got restless. 



We feel assured, however, that a change of the animal's position 

 can exert an influence upon the nystagmus, so that e. g. the fre- 

 quency is always less with ventral position than with a dorsal 

 position, and this holds good for the caloric as well as for the 

 spontaneous nystagmus showing itself after a unilateral extirpation 

 of the labyrinth. 



Similarly it is often very difficult to accurately determine the 

 nature of the nystagmus. It happens again and again that the caloric 

 nystagmus in a certain position is perfectly horizontal for some time 

 and suddenly turns rotatory, without any assignable cause. After a 

 change of the animal's position we invariably delayed noting down 

 the nature of the nystagmus for some moments, in order to [)reclude 

 the chance that the nystagmus brought forth by the change of the 

 animal's position should interfere with the caloric phenomenon. The 

 terms: nystagmus to the left or to the right always mean a nys- 

 tagmus with the fast component to the left or to the right. From 

 this inquiry it became evident that the direction of the spontaneous 

 nystagtnus is not in all positions identical with that of the caloric 

 nystagmus, as it appeared that the spontaneous nystagmus occurring 

 after unilateral extirpation of the labyrinth, has in all positions the 

 fast component turned towards the unimpaired labyrinth, whereas 

 the caloiic nystagmus is, with ventral position and with vertical 

 j)Osition (hfuid up), turned towards the non-irrigated ear ; with dorsal 

 position and with vertical position (head down) it is turned towards 

 the irrigated ear; with lateral position (5 and 6) the caloric nys- 

 tagmus is mostly towards the same side as with ventral position. 



Ad b. Directly after extirpation of a labyrinth a nystagmus reveals 

 itself spontaneously towards the side of the unimpaired labyrinth. 

 As appeared sub a, this nystagmus does not v^ary its direction witli 

 a change of the animal's position in space. When both labyrinths 

 are removed during the operation with only a very short interval, 

 no nystagmus will occur. If, therefore, caloric nystagmus should be 

 identical with elimination of the labyrinth, it must be possible to 

 arrest in all positions the nystagmus occurring after unilateral extir- 

 pation of the labyrinth, by allowing water to flow into the unim- 

 paired ear. This, in fact, is not the case, as was evidenced by four 

 experiments upon cats,, which all yielded similar results. This may 

 be instanced by the following abridged protocol : 



31-5-1917. Oa.t. A flow of cold water 11—12° into the right 

 meatus auditorius from 1,5 m. 



