898 THE CEREBELLUM. 



in those which fix the vertebral column. Unsteadiness is most marked 

 in the movements of the neck. A residuum of disturbance of rnotility 

 is permanent; but in Luciani's dog, which lived for two years after 

 ablation of the whole cerebellum (except for two small pieces adjoining 

 the fiocculi), improvement (compensation) progressed for about a year. 

 The hind-quarters remained weak, tremor persisted in the muscles which 

 fix the head, and the movement of the eyes and limbs, especially of the 

 fore-limbs, were not perfectly harmonic. The senses and intellect 

 remained perfect, and the animal could swim, run, jump, and feed itself. 

 On the whole, perhaps the most significant symptom of cerebellar 

 ablation is the tremor which disturbs willed movements "intention 

 tremor." I have myself seen it in the dog persisting two years after 

 an ablation of almost the whole cerebellum. The animal when resting, 

 e.g. lying in his cage, exhibited no tremulance ; but on being called to 

 activity, especially when released from his cage, and free and evidently 

 pleasurably excited by his freedom, one saw almost his every motion 

 shaken by tremor. 



Destruction of the middle lobe. The main phenomena following 



this lesion are opisthotonos, re- 

 traction of the neck, vertical 

 nystagmus, abduction and exten- 

 sion of all four limbs (especially 

 of the anterior), some weakness 

 and tremor in all four limbs 

 (especially in the posterior). 

 When trying to walk forward, 

 the animal often, instead of ad- 

 vancing, retreats. 1 These dis- 



FIG. 366. -Gait after destruction of the turbances subside much more 

 vermis ; the fore-limbs are abducted, the rapidly and completely than after 

 hind are abducted and protracted. ablation of the whole cerebellum. 



Thomas (from an instantaneous photo- -,-,. ,. , , , ,, 



graph). Bisection of the cerebellum. 



The splitting of the organ into 



its two lateral halves' by a clean incision is followed by disturbances 

 closely like those following ablation of the vermis, but of less severe 

 and less persistent character. " The animal seemed alternately im- 

 pelled to right and to left, without preserving a fixed position ; it first 

 rolled a turn or two to one side, and then changed, as for relief, to turn 

 as many times in the opposite direction." 2 As an early symptom it 

 generally induces a tonic extensor rigidity, comparable with the ex- 

 tensor form of decerebrate rigidity. 3 



Ablation of the cerebellum in the bird. In the pigeon, 4 ablation 

 of the cerebellum similarly produces malposture and a status in which 

 each intentional movement is hampered or thwarted by uncontrollable 

 deviation from the desired direction ; abrupt oscillations seem grafted 

 upon the movements executed. It is impossible for the animal to 

 perch, the legs and talons being stiffly extended. In attempting to 

 walk, the limbs become seized with extensor spasm ; the animal 

 falls; wild struggling of limbs, body, and head sets in, to terminate 

 only in utter exhaustion. There is obvious difficulty in bending 



1 A. Thomas, loc. cit. 2 Magendie, loc. cit. 



" Sherrington, Journ. Physiol., Cambridge and London, vol. xxii. p. 319. 

 4 Fiourens' classical observations (1822) were chiefly' on the pigeon. 



