10 



Scientific Proceedings. 



the injured side on attempting to stand. It may roll completely 

 over on the floor. There is a quick movement of the eyes toward 

 the sound side and a slow return to the injured side. The un- 

 steadiness of gait and the nystagmus are transient. Marked 

 torsion of the head is permanent (two years). 



Stimulation of the labyrinth, under moderate anesthesia, by 

 putting hot water in the trephine opening before destruction of 

 the semi-circular canals, causes slow marked deviation of both 

 eyes to the opposite (unstimulated) side. Ice in the trephine hole 

 causes the eyes to deviate to the same (stimulated) side. On 

 electrical stimulation, the zinc terminal of a battery causes devia- 

 tion to the opposite side; the carbon terminal, to the same side. 



The deviation of the eyes on stimulation of the labyrinth may 

 be obtained after total removal of the cerebrum, the optic thala- 

 mus, the anterior portion of the anterior corpora quadrigemina 

 and the cerebellum. The torsion of the head in tortoises following 

 destruction of one labyrinth is as marked after decerebration as 

 before. There are no apparent "shock" phenomena in these 

 reflexes after decerebration. 



The nystagmus is not due to irritation of the wound, but to 

 the action of the opposite uninjured labyrinth. Nystagmus fol- 

 lowing extirpation of the second labyrinth is much less marked, 

 and more fleeting than after extirpation of the first, and is re- 

 versed in direction, i. e., the quick movement is to the injured side. 



There is no torsion of the body nor any rolling movements 

 after extirpation of both labyrinths at the same operation, nor 

 when the second labyrinth is destroyed after an interval. The 

 animal becomes very ataxic and is unable to grasp food if both 

 labyrinths are removed at the same time. 



Complete or partial removal of the cerebellum one or two 

 weeks previous to removal of one labyrinth has no effect upon the 

 onset and course of labyrinthine nystagmus. Eye movements 

 following injury to the cerebellum are jerky, irregular, and quick 

 in all directions. Labyrinthine nystagmus is slow in one direction 

 and quick in the opposite direction. The eye movements following 

 cerebellar extirpation greatly outlast those of labyrinthine origin, 

 and the labyrinthine movements may be superposed on those 

 following cerebellar removal. 



