432 THE BRAIN. 



moves sluggishly and unwillingly, but otherwise acts in a perfectly 

 natural manner. The second pigeon, on the other hand, from 

 whom the cerebellum only has been taken away, is in a constant 

 state of agitation. He is easily terrified, and endeavors, frequently 

 with violent struggles, to escape the notice of those who are 

 watching him; but his movements are sprawling and unnatural, 

 and are evidently no longer under the effectual control of the will. 

 (Fig. 142.) If the entire cerebellum be destroyed, the animal is 

 no longer capable of assuming or retaining any natural posture. 

 His legs and wings are almost constantly agitated with ineffectual 

 struggles, which are evidently voluntary in character, but are at 

 the same time altogether irregular and confused. Death generally 

 takes place after this operation within twenty-four hours. 



We have often performed the above operation, and always with 

 the same effect. Indeed there are few experiments that have been 

 tried upon the nervous system, which give results so uniform and 

 so constant as this. Taken by themselves, these results would 

 invariably sustain the theory of Flourens, which, indeed, is founded 

 entirely upon them. 



But we have met with another very important fact, in this respect, 

 which has hitherto escaped notice. That is, that birds, which have 

 lost their power of muscular co-ordination from injury of the cere- 

 bellum, may recover this power in process of time, notwithstanding that 

 a large portion of the cerebellum has been permanently removed. 

 Usually such an operation upon the cerebellum, as we have men- 

 tioned above, is fatal within twenty-four hours, probably on account 

 of the close proximity of the medulla oblongata. But in some 

 instances, the pigeons upon which we have operated have survived, 

 and in these cases the co-ordinating power became re-established. 



In the first of these instances, about two-thirds of the cerebellum 

 was taken away, by an opening in the posterior part of the cranium. 

 Immediately after the operation, the animal showed all the usual 

 effects of the operation, being incapable of flying, walking, or even 

 standing still, but reeled and sprawled about in a perfectly helpless 

 manner. In the course of five or six days, however, he had regained 

 a very considerable control over the voluntary movements, and at 

 the end of sixteen days his power of muscular co-ordination was 

 so nearly perfect, that its deficiency, if any existed, was impercep- 

 tible. He was then killed; and on examination, it was found that 

 his cerebellum remained in nearly the same condition as immediately 

 after the operation ; about two-thirds of its substance being deficient, 



