Unilateral Removal of the Otic Labyrinth. 135 



decerebration. Before decerebration the animals presented no 

 disturbances of equilibrium. For several hours after this opera- 

 tion the animals presented all the bodily reactions which appear 

 on the first day following unilateral removal of the labyrinth. 

 The protocols of one of these experiments follow : 

 Kitten, weight 1450 g. 



Feb. 15, 1917. Right otic labyrinth removed under asepsis. 

 Operation followed by nystagmus and typical disturbances of 

 equilibrium, violent in character. 



March 3 (16 days following labyrinthine operation). 



2.40 P. M. Decerebration under ether. Section just anterior 

 to corpora quadrigemina. 



2.55 to 6.30 P. M. Marked and permanent deviation of eyes 

 to right (side of labyrinthine lesion). Animal tied to turntable 

 with the head fixed in the vertex upward position. When the 

 direction of rotation is toward the side of the labyrinthine lesion, 

 the deviation of the eyes is intensified on cessation of rotation. 

 The eyes then return slowly to the initial position of deviation. 

 When the direction of rotation is toward the intact labyrinth, 

 deviation entirely disappears on cessation of rotation; the eyes 

 then return slowly to the initial position of deviation. Animal 

 removed from rotation board. When removed from the board, 

 the animal lay on its right side with fore limbs extended. The 

 neck was bent to the side of the labyrinthine lesion. Marked 

 increase in torsion of the head, occiput pointing to the right. 

 When disturbed by pinching the tail, the animal made violent 

 attempts to turn on its dorso-ventral axis toward the side of the 

 labyrinthine lesion. The forelimbs participated actively in the 

 attempts to turn to the right. When the animal was placed on 

 its back or on its left side, it immediately rolled to the right and 

 came to rest in the position described. 



6.30 P. M. Observations made at frequent intervals since 

 last note without noticeable changes in the reactions. 



Conclusions. 



The disappearance of the ocular and the equilibrium disturb- 

 ances following unilateral removal of the labyrinth is attributed 

 to the activity of a compensatory mechanism. 



