ABLATION OF THE CEREBELLUM. 



899 



the neck downward, and when the head is at last sufficiently lowered 

 it is liable to be suddenly and uncontrollably drawn back (Schiff, 1 

 Lange 2 ) ; hence the animal cannot at first feed itself. The difference 

 between this condition and that resulting from ablation of the cerebral 

 hemispheres is very marked. " Take two pigeons," wrote Longet, 

 " from one remove the cerebrum, from the other only half the 

 cerebellum ; next day the former will be firm on his feet, the 

 latter will reel and struggle like a drunken man." 3 But the severity 

 of the disturbance soon diminishes. 4 It is notable that night very 

 rapidly recovers. Pigeons soon fly adroitly and turn apparently perfectly 

 in the , cramped space of a room. Walking is more slowly and less 

 perfectly regained. In the decerebellate pigeon it can be seen that the 

 front digits are over-extended when it walks, and the hind digit does 

 not touch the floor at all. 5 Perching remains a difficulty for a long 

 time ; at the moment of alighting, the legs and talons become suddenly 

 rigid in extension, defeating as it were their own intention. The move- 



Fig. 367. — Pigeon after removal of the cerebellum (Dalton). 



ments are most distraught when the creature is excited and seems at 

 greatest pains to execute them. 



Ablation of the cerebellum in lower vertebrates.— In the lizard 

 and tortoise, little disturbance appears to result from ablation of the 

 cerebellum. 6 Dickinson says that when in the snake the lateral con- 

 nections of the cerebellum are severed on one side, the animal's posture 

 becomes twisted to a spiral. 



In the frog the cerebellum is small, a simple transverse band jutting 

 over the fourth ventricle. Many observers state that its removal or 

 destruction occasions no obvious departure from normality. But Budge 7 

 noted that after ablation of one lateral half, e.g. right, the animal sits 

 with the right side lower than the left, with the spine concave to the 

 right, and with the digits of the left hind-foot extended. The animal 

 can be made to lie on its right side, but never on its left. In crawling 

 or springing forwards, there is deviation towards the right. Goltz 8 



1 Op. cit. 



■' Lange, loc. cit. 



7 Loc. cit. 



- Op. cit. 



3 Op. cit. A Luciani, op. cit. 



6 Desmoulins, loc. cit.; Dickinson, etc., loc. til, 



8 Loc. cit. 



