1894.] Researches into the Functions of the Cerebellum. 59 



even three months after the half of the cerebellum had been re- 

 moved. The results obtained when absinthe was administered to 

 animals which had been deprived of half the cerebellum also yielded 

 highly interesting and instructive results. The increased excitability 

 of the opposite hemisphere was evidenced by the exaggeration of the 

 convulsions on the side of the cerebellar lesion ; and it became also 

 evident that the convulsions on the opposite side were diminished. 

 Further, the curves obtained from the extensor muscles of the 

 anterior extremity on the side of the cerebellar lesion showed that 

 there was a marked alteration in the second stage of the convulsive 

 seizure, for the tonus characteristic of this stage of similar convul- 

 sions evoked in. dogs whose central nervous system was intact was 

 either replaced by clonic spasms, or a large element of clonus was 

 superimposed on the tonus. The curves from the muscles of both 

 anterior extremities showed this alteration in the second stage of the 

 convulsions when the whole instead of the half of the cerebellum 

 had been previously removed. 



The chief conclusions which appear to be warranted are that the 

 one half of the cerebellum does not, in any great measure, depend on 

 the cooperation of the other half for the proper performance of its 

 functions. The bulk of the impulses pass from one half of the organ 

 to the cerebrum, or spinal cord, without passing to the other half. 

 Three factors are responsible for the defective movements which re- 

 sult on ablation of different parts of the organ incoordination, 

 rigidity, and motor paresis. The last of these is probably di- 

 rectly due to the withdrawal of the cerebellar influence from the 

 muscles, while the exalted excitability of the opposite cortex cerebri, 

 which results after unilateral ablation of the cerebellum, is probably 

 a provision for compensation in this and other connexions. The one 

 half of the cerebellum controls the cells of the cortex of the opposite 

 cerebral hemisphere, and those of the anterior horns of the spinal 

 cord on the same side chiefly, and on the opposite side to a slight 

 extent. It is further suggested that either the cerebral hemisphere 

 whose excitability is increased inhibits the opposite hemisphere, or 

 that, under normal conditions, one half of the cerebellum inhibits the 

 other half, which inhibition being no longer operative, owing to 

 ablation of half of the organ, allows the remaining half to exert an 

 increased control on the opposite cortex cerebri, or on the spinal 

 centres of the same side, or possibly in both directions ; but which is 

 the most probable explanation of the phenomena observed is at pre- 

 sent left an open question. 



The symptoms characteristic of unilateral ablation of the cerebellum 

 are: 



1. Rotation and reeling to the opposite side. 



2. The side of the face corresponding to the side of the lesion is 



