Page:Proceedings of the Royal Society of London Vol 60.djvu/221

Rh possible control which the cei’ebellum may exert on the spinal centres. The state of the knee-jerks afforded no satisfactory inform ation on this point.

The blunting of sensibility m et w ith is held to be fu rth er proof th at the cerebellum is concerned w ith sensory as well as motor p rocesses, as was contended by th e auth o r in a form er paper.

Faradic excitability of the opposite cerebral hemisphei*e was found to be less th an of th a t on the side of the lesion, both w hen the in ­ ferior cerebellar peduncle was divided, and when partial hemisection of the medulla was performed, leaving th e pyram id intact. The most satisfactory explanation of this phenom enon appears to be th a t the removal of some afferent inhibitory influence from one half of the cerebellum allows this half of the organ to fu rth er inhibit the cortex of the opposite cerebral hem isphere ; an explanation in keeping with th at offered w hen th e results of ablation of th e cerebellum were under consideration.

This view is strengthened by the rem arkable results obtained by the intravenous injection of absinthe in anim als in whom the same lesions had been previously produced, for with the pyram idal system absolutely intact on both sides, there was an entire absence of contraction of the muscles of the anterior extrem ity on the side of the lesion, and dim inution of contraction of the muscles of the posterior extrem ity on this side, as com pared w ith those of the opposite limb. Such was the result obtained when the convulsions were induced soon after the lesion, but when induced at some remote period, such as three weeks after, the muscles of the anterior extrem ity on the side of the lesion contracted, though the contractions were m uch less powerful than were those of the opposite anterior extrem ity, and were often largely tonic in character.

Transverse section of the posterior columns, and th eir nuclei alone on one side, did not alter the character of the absinthe convulsions in such a remarkable m anner as did division of the peduncle and lateral section of the medulla. A fter such a lesion the m uscular contractions in the anterior extrem ity on the side of the lesion were less powerful than were those in the opposite anterior extrem ity, and there was more tonus and less clonus than in the contractions on the opposite side. Both these characters were evident in the early convulsions of a series, but became much more pronounced in the later convulsions. The author contents himself w ith recording these facts, and makes no attem pt to speculate as to their probable significance.

The paper is illustrated by tracings obtained of the m uscular contractions resulting from excitation of the cerebral cortex w ith the induced current, and from the convulsions evoked by the intravenous injection of absinthe, and dem onstrate the points alluded to in th at part of the text which deals w ith these phenomena.