688 



FUNCTIONS OF THE CEREBELLUM. [CH. XLIX. 



Thus if the horizontal canal is divided in a pigeon, the head is 

 thrown into a series of oscillations in a horizontal plane, which 

 are increased by section of the corresponding canal of the opposite 

 side. After section of the vertical canals, the forced movements 

 are in a vertical plane, and the animal tends to turn somersaults. 



" When the whole of the canals are destroyed on both sides 

 the disturbances of equilibrium are of the most pronounced 

 character. Goltz describes a pigeon so treated which always 

 kept its head with the occiput touching the breast, the vertex 

 directed downwards, with the right eye .looking to the left and 

 the left looking to the right, the head being incessantly swung 

 in a pendulum-like manner. Cyon says it is almost impossible to 

 give an idea of the perpetual movements to which the animal is 

 subject. It can neither stand, nor lie still, nor fly, nor maintain 



Fig. 512. Diagram of semicircular canals, to show their positions in three planes at right 

 angles to each other. It will be seen that the two horizontal canals (H) lie in the 

 same 'plane : and that the superior vertical of one side (S) lies in a plane parallel to 

 that of the posterior vertical (P) of the other. (After Ewald.) 



any fixed attitude. It executes violent somersaults, now r forwards, 

 now backwards, rolls round and round, or springs in the air and 

 falls back to recommence anew. It is necessary to envelope the 

 animals in some soft covering to prevent them dashing themselves 

 to pieces by the violence of their movements, and even then not 

 always with success. The extreme agitation is manifest only 

 during the first few days following the operation, and the animal 

 may then be set free without danger ; but it is still unable to 

 stand or walk, and tumultuous movements come on from the 

 slightest disturbance. But after the lapse of a fortnight it is 

 able to maintain its upright position with some support. At this 

 stage it resembles an animal painfully learning to stand and walk. 

 In this it relies mainly on its vision, and it is only necessary to 

 cover the eyes with a hood to dispel all the fruits of this new 

 education, and cause the reappearance of all the motor disorders.' 

 (Ferrier.) 



