200 Dr. Russell. Phenomena resulting from Interruption 



obtained afford valuable information with regard to many of the 

 functions of the cerebellum ; but they are not claimed as supplying 

 definite information on the important question as to whether the 

 cerebellum exercises a direct downward influence on the spinal 

 centres or not. Many of the results obtained suggest the possibility 

 of such a downward influence ; but most of the effects can as readily 

 be explained by supposing that they are the result of the interruption 

 of afferent impulses passing from the periphery to the cerebellum. 



The direction of rotation was towards the side of the lesion after 

 division of one inferior peduncle, or in other words if, as was always 

 the case, the left peduncle was divided, the animal rotated like a right 

 handed screw entering an object. The direction of rotation was 

 thus the same as after intracranial section of the auditory nerve, and 

 the reverse of what results on ablation of one lateral half of the 

 cerebellum. The bulk of the afferent impulses, whose interruption is 

 responsible for this phenomenon, probably reach the inferior peduncle 

 from the auditory nerve, but that all the impulses are not derived 

 from this source was shown by the fact that lateral section of the 

 medulla below the auditory nerve and its nuclei may result in similar 

 rotation. 



The disorders of motility which followed division of one inferior 

 peduncle corresponded exactly with those observed after ablation of 

 one lateral half of the cerebellum. In view of the results obtained 

 by Claude Bernard, and by Mott and Sherrington, as regards im- 

 pairment of movement after section of sensory spinal roots, it is 

 suggested that the defects of movement which result from section of 

 one inferior cerebellar peduncle may be due to the interruption of 

 such afferent impulses passing to the cerebellum, rather than to the 

 cutting off of efferent impulses from the cerebellum to the spinal 

 centres, The way in which the sensory defects correspond in dis- 

 tribution to the motor, and the fact that recovery of sensory conduc- 

 tion commences before any improvement in motor power can be 

 detected, are held to support this view. 



Cutting off of some afferent impulses can alone be considered 

 responsible for the ocular displacements met with. These displace- 

 ments correspond with those which are the result of ablation of one 

 lateral half of the cerebellum, the displacement of the globes being 

 downward and to the opposite side from the lesion. The displace- 

 ments following lateral section of the medulla were the same; but 

 after division of the posterior columns and their nuclei on one side, 

 the displacement of the globes was downward and to the side of the 

 lesion. 



Spasm, which was easily detected in the back and neck muscles on 

 the side of the lesion, causing incurvation of the vertebral axis to that 

 side, alone furnished any satisfactory information in support of the 



