THE CEREBELLUM. 495 



Aside from the particulars above mentioned, experiments which con- 

 sist in mutilation or removal of the cerebellum have yielded very uni- 

 form results of a striking character, and not similar to those caused by 

 injury to other parts of the brain. These effects were first described by 

 Flourens in 1842; 1 and notwithstanding the great activity of research 

 upon the nervous system since that time, the results obtained by him 

 have been uniformly corroborated in all essential particulars by subse- 

 quent observers. The phenomena, which are of a similar nature in 

 different species of animals, have been seen, by Flourens or others, in 

 the pigeon, fowl, duck, turkey, and other birds ; and, among quadrupeds, 

 in the dog, the cat, the mole, the rat, and the guinea pig. 



The effect produced by destruction or removal of the substance of the 

 cerebellum consists in a peculiar disorder of the movements of the body 

 and limbs, from want of harmony in their muscular action. The power 

 of associating the contractions of different muscles, in such a way as to 

 produce co-ordinated movements, is lost or impaired in proportion to 

 the injury inflicted upon the nervous centre. If in a living pigeon the 

 cerebellum be exposed, and a portion of its substance removed, the 

 animal exhibits at once a characteristic uncertainty in the gait, and in 

 the movement of the wings. If the injury be more extensive, the bird 

 loses altogether the power of flight, and can walk, or even stand, only 

 with difficulty. This is not owing to any actual paralysis, for the 

 movements of the limbs are often quite rapid and energetic ; but is due 

 to a deficient control over the muscular contractions, similar to that 

 seen in a man in a state of intoxication. The movements of the legs 

 and wings, though forcible, are confused and blundering ; so that the 

 animal cannot direct his steps to any particular spot, nor support him- 

 self in the air by flight. He reels and tumbles, but can neither walk 

 nor fly. 



The senses and the intelligence are at the same time unimpaired, and 

 this circumstance causes a striking difference between the phenomena 

 produced by removal of the cerebrum, and those following removal of 

 the cerebellum. If these two operations be done upon different pigeons, 

 and the two animals placed side by side, the first pigeon, from which 

 the cerebrum only has been removed, remains standing firmly upon his 

 feet, in a condition of complete repose; and when compelled to stir, 

 he moves sluggishly and unwillingly, but otherwise acts in a perfectly 

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

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

 agitation. He is easily excited, and frequently endeavors, with violent 

 struggles, to escape from one place to another ; but his movements are 

 sprawling and unnatural, and no longer under the effectual control of 

 the will. If the entire cerebellum be destroj'ed, the animal is incapable 

 of assuming or retaining any natural posture. His legs and wings are 



1 Recherches Exp6rimentales sur les Propri6t6s et les Fonctions du Systfeme 

 Nerveux. Paris, 1842, pp. 37, 53, 102, 133. 



