438 THE NERVOUS SYSTEM. 



any existed, was imperceptible. He was then killed, and on examina- 

 tion 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, with no regeneration of the lost parts. The 

 accompanying figures show the appearances in this brain as compared 

 with that of a healthy pigeon. 



In the three remaining cases the quantity of nervous substance 

 removed amounted to about one-half of the cerebellum. The loss of 

 coordinating power, immediately after the operation, though less com- 

 plete than in the preceding instance, was perfectly well marked ; and 

 in little more than a fortnight the animals had nearly or quite recovered 

 control of their motions, so far as could be seen while they were under 

 observation. 



It is evident that in these cases, if the cerebellum be really the physi- 

 ological seat of coordinating power, there are two distinct effects pro- 

 duced by the operation. The first is the shock due to the sudden injury 

 of the cerebellum as a whole. This effect is temporary, and may be 

 recovered from in time, provided the animal survive the immediate 

 injury. The remaining effect is that due to the loss of nervous sub- 

 stance ; and this effect must of course be permanent, unless the ner- 

 vous matter be regenerated. In the cases detailed above, the greatest 

 amount of disturbance seems to have depended on the sudden injury 

 to the nervous centre as a whole ; and the animals recovered, to a 

 great extent, their power of coordination, notwithstanding that from 

 one-half to two-thirds of the cerebellum was permanently lost. 



The recovery of a nervous function, after loss of substance, is not 

 peculiar to the cerebellum. Flourens observed the same thing in 

 regard to the cerebral hemispheres in the pigeon : the perceptive 

 faculties being totally suspended by removal of a portion of the hemi- 

 spheres, and again restored after several days. But this restoration 

 only takes place where the removal of the nervous centre is partial ; 

 and in the cerebellum, as well as in the cerebrum, after complete extir- 

 pation, the loss of function is permanent. In the experiment of 

 Flourens, where a fowl lived for four months after entire removal of 

 the cerebellum, there was no recovery of coordinating power. 



The recovery of this power after partial loss of the cerebellum may 

 be also in some measure apparent rather than real. The animals may, 

 after a time, cease attempting the more complicated movements of which 

 they are incapable, and confine themselves to the simpler acts which 

 they can still accomplish. A pigeon, furthermore, when confined to 

 the limited space of a laboratory, has no opportunity for the many 

 varied evolutions of natural flight ; and it is possible that he might 

 be permanently incapacitated for such movements, while showing no 

 deficiency in the ordinary acts of standing or progression. 



The same remark will apply to certain pathological observations in 

 man, which have been sometimes considered as neutralizing the results 

 of experiment on this subject. These are mainly cases in which lesions 



