FUNCTIONS OF THE CEREBELLUM. 709 



Extirpation of the Cerebellum in the lower Animals. In birds, and in certain mam- 

 mals in which the operation has been successful, the more or less complete extirpation 

 of the cerebellum is followed by well-marked phenomena, which present always the same 

 character but are somewhat differently interpreted by various experimenters. Experi- 

 ments of this kind were first made by Flourens ; and the accuracy of his observations 

 has never been successfully controverted, whatever may have been said of his physiolo- 

 gical deductions. Indeed, there are few if any important points in the phenomena fol- 

 lowing partial or complete removal of the cerebellum that escaped the attention of this 

 most accurate observer. 



Laying aside, for the present, the deductions to be made from experiments upon ani- 

 mals, we may quote the following phenomena noted by Flourens and by all who have 

 repeated his observations upon the cerebellum : 



" I extirpated the cerebellum by successive layers in a pigeon. During the removal 

 of the first layers, there only appeared slight feebleness and want of harmony in the 

 movements. 



" At the middle layers, there was manifested an almost universal agitation, although 

 there was not added any sign of convulsion ; the animal executed sudden and disordered 

 movements ; it heard and saw. 



" On the removal of the last layers, the animal, the faculty of jumping, flying, walk- 

 ing, and maintaining the erect position being more and more disturbed by the preceding 

 mutilations, lost this faculty entirely. 



" Placed on the back, it was not able to recover itself. Far from resting calm and 

 steady, as occurs in pigeons deprived of the cerebral lobes, it became vainly and contin- 

 ually agitated, but it never moved in a firm and definite manner. 



" For example, it saw a blow with which it was threatened, wished to avoid it, made 

 a thousand efforts to avoid it, but did not succeed. If it were placed on its back, it would 

 not rest, exhausted itself in vain efforts to get up, and finished by remaining in that posi- 

 tion in spite of itself. 



" Finally, volition, sensation, perception, persisted ; the possibility of making general 

 movements persisted also ; but the coordination of the movements in regular and definite 

 acts of locomotion was lost." 



The above are the phenomena observed after total extirpation of the cerebellum. 

 Voluntary movement, sensation, general sensibility, and the special senses, seem to be 

 intact ; but there is always a loss of the power of equilibrium, and the movements exe- 

 cuted are never regular, efficient, and coordinate. Flourens farther states that animals 

 operated upon in this way retain their intellectual and perceptive faculties. 



It is exceedingly important now to note the effects of partial removal of the cerebel- 

 lum, as these bear directly upon cases of disease or injury of this organ in the human 

 subject, in which its disorganization is very rarely complete. We may illustrate this, 

 also, by citing two of Flourens's typical experiments : 



" I. I removed by successive layers, all of the upper half of the cerebellum in a 

 young cock. 



" The animal immediately lost all stability, all regularity in its movements ; and its 

 tottering and bizarre mode of progression reminded one entirely of the gait in alcoholic 

 intoxication. 



" Four days after, the equilibrium was less disturbed, and the progression was more 

 firm and assured. 



" Fifteen days after, the equilibrium was completely restored. 



" II. I removed, in a pigeon, about the half of the cerebellum ; and I removed this 

 organ completely in a fowl. 



" At the end of a certain time, the pigeon had regained its equilibrium ; the fowl 

 did not regain it at all : the latter lived nevertheless for more than four months after 

 the operation." 



