498 THE BKAIN. 



The recovery of a nervous function, after permanent loss of nervous 

 substance, is not peculiar to the cerebellum. Flourens has observed 

 the same thing in regard to the cerebral hemispheres in the pigeon; 

 the intellectual and perceptive faculties being totally suspended im- 

 mediately after partial removal of the hemispheres, but again restored 

 after the lapse of several days. But this restoration only takes place 

 where the removal of the nervous centre is partial ; and in the cerebel- 

 lum, as well as in the cerebrum, after complete extirpation, the loss of 

 function is a permanent one. In the experiment of Flourens, where a 

 fowl lived for four months after entire removal of the cerebellum, there 

 was no recovery of co-ordinating power. 



It is to be remembered that birds and other animals, when confined to 

 the limited space of a laboratory, have no opportunity of exercising the 

 more complicated and active movements natural to them in a condition 

 of freedom ; and accordingly, they might not show any great deficiency 

 of muscular co-ordination while in confinement, though they might still 

 be incapable of executing all the movements of natural flight. The 

 simpler motions may continue to be performed with only a part of the 

 cerebellum remaining ; but we are not sure that, even in these cases, a 

 portion of the co-ordinating power, corresponding with the destruction 

 of nervous substance, has not been permanently lost. 



II. Pathological Observations in the Human Subject. The same re- 

 mark will apply to the pathological observations in man which have been 

 sometimes considered as neutralizing the result of experiments. These 

 are mainly cases in which lesions of the cerebellum, more or less ex- 

 tensive, have existed without recorded disturbances of co-ordination 

 similar to that produced in animals by mechanical injury of the part. 

 In a large majority of these instances the patients were confined to a 

 sick-room, and in many of them to the bed ; consequently there could 

 be no opportunity of observing a want of natural co-ordination in the 

 more complicated movements, if any such existed. A patient, also, in 

 whom the loss or diminution of a motor nervous function comes on 

 gradually, accommodates himself to it by abstaining from the attempt 

 to perform movements of which he is incapable, and confines himself to 

 those which he is still able to perform. Furthermore, in many cases of 

 disease of the cerebellum, symptoms of want of co-ordinating power 

 have been distinctly noticed and recorded. 



The data derived from comparative anatomy show a general corre- 

 spondence in the development of the cerebellum and the variety and 

 complication of muscular action. In fish, as a rule, it is of good size 

 compared with other parts of the brain; and although direct progression 

 in this class is accomplished by a comparatively simple mechanism, 

 namely, the lateral flexion and extension of the spinal column with its 

 expanded fins and tail, yet their movements through the water or in 

 leaping out of it, while pursuing and taking their prey, are remarkably 

 rapid and vigorous, and are promptly varied in any direction. In the 

 frog, on the other hand, the movements of progression consist of little 



