THE NERVOUS SYSTEM AND CONSCIOUSNESS. 745 



The transverse fibers of the pons Varolii unite the lobes of the 

 cerebellum, and we may appropriately consider the functions of this 

 organ before those of the smaller masses within the cerebral hemi- 

 spheres. There is, perhaps, no subject in nerve-physiology more ob- 

 scure and difficult than this one of the functions of the cerebellum. 

 The earlier opinion, that this organ is connected with the sexual appe- 

 tite, has long since been completely disproved. The special difficulty 

 in determining the functions of the cerebellum arises from the dis- 

 agreement between experiment and pathology, as also from hazard of 

 injury to adjacent nerve-masses. Flourens was the first to investigate 

 the functions of the cerebellum in a strictly inductive manner ; his 

 experiments have been repeatedly confirmed, and they must furnish 

 the starting-point for all future inquiry. Flourens says : " I removed 

 the cei'ebellum of a pigeon in successive slices. During the removal 

 of the first layers there appeared only a weakness and want of har- 

 mony in its movements. On removal of the middle layers, the animal 

 exhibited a general agitation, without true convulsions. It made 

 brusque and irregular movements, and continued loath to see and to 

 hear. On removal of the last layers, the animal entirely lost the 

 power of standing, flying, leaping, or walking, which had been gradu- 

 ally affected by the preceding mutilation. Placed on its back, it was 

 unable to rise. Instead of remaining quiet and immovable, like 

 pigeons deprived of their hemisiDheres, it was in a continual state of 

 restlessness and agitation, but could never make any determinate 

 movement. It could see a threatened blow, and tried to escape, but 

 without success. It made various efforts to recover its station when 

 laid on its back, but utterly failed to do so. Sensation, volition, and 

 intelligence remained, but the co-ordination of movements into regu- 

 lar and determinate movements of progression was entirely lost." 

 There is no doubt that destruction of the cerebellum is frequently fol- 

 lowed by striking disorders of equilibrium. Flourens found, however, 

 that these disorders would, in time, be overcome by the animal, even 

 though the lesions were deep. Upon complete destruction of the or- 

 gan, the disorders were lasting. Weir Mitchell's experiment, quoted 

 by Ferrier, would not confirm this permanency of the disorders. 

 Weir Mitchell states that he destroyed the functional activity of the 

 entire cerebellum in pigeons who, after some months, recovered " so 

 far as to show only feebleness and incapacity for prolonged muscular 

 exertion, but no real inco-ordination or unsteadiness of equilibrium." 

 Repeated experiments have shown a decided difference of result, ac- 

 cording to the character and location of the lesions. If these lesions 

 are made symmetrically on both sides, or if the cerebellum be divided 

 in the middle, from the front backward, there is no important disturb- 

 ance of equilibrium. If, on the other hand, the central lobe be cut in 

 its anterior portion, the animal tends to fall forward ; if in its poste- 

 rior portion, to fall backward. Lesion in one of the lateral lobes is 



