Page:Proceedings of the Royal Society of London Vol 60.djvu/220

200 obtained afford valuable information with regard to m any 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 spina] 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 rig h t 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 w hat 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 th e inferior peduncle from the auditory nerve, b u t th a t all the impulses are not derived from this source was shown by the fact th a t lateral section of the medulla below the auditory nerve and its nuclei may result in sim ilar rotation.

The disorders of m otility which followed division of one inferior peduncle corresponded exactly w ith those observed after ablation of one lateral half of the cerebellum. In view of the results obtained by Claude Bernard, and by M ott and Sherrington, as regards im ­ pairm ent of movement after section of sensory spinal roots, it is suggested th a t the defects of movement w hich result from section of one inferior cerebellar peduncle m ay be due to the interruption of such afferent impulses passing to the cerebellum, rath er th an to the cu ttin g off of efferent impulses from the cerebellum to the spinal •centres. The way in which the sensory defects correspond in distribution to the motor, and the fact th a t recovery of sensory conduction commences before any im provem ent 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 m et with. These displacem ents correspond w ith those which are th e 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 displacements 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 th at side, alone furnished any satisfactory information in support of the