

FUNCTIONS OF THE CEREBELLUM. 515 



paratively little occasion for any organ to combine and harmonize 

 the actions of their several muscles ; and in these, the Cerebellum is 

 usually small. But among the more active predaceous Fishes (as the 

 Shark), Birds of the most powerful and varied flight (as the Swallow), 

 and such Mammals as can maintain the erect position, and can use their 

 extremities for other purposes than support and motion, we find the 

 Cerebellum of much greater size, relatively to the remainder of the 

 Encephalon. There is a marked advance in this respect, as we ascend 

 through the series of Quadrumanous animals ; from the Baboons, which 

 usually walk on all-fours, to the semi-erect Apes, which often stand and 

 move on their hind-legs only. The greatest development of the Cere- 

 bellum is found in Man ; who surpasses all other animals in the number 

 and variety of the combinations of muscular movement which his ordi- 

 nary actions involve, as well as of those which he is capable, by prac- 

 tice, of learning to execute. 



909. From experiments upon all classes of Vertebrated animals, it 

 has been found that, when the Cerebellum is removed, the power of 

 walking, springing, flying, standing, or maintaining the equilibrium of 

 the body, is destroyed. It does not seem that the animal has in any 

 degree lost the voluntary power over its individual muscles ; but it can- 

 not combine their actions for any general movements of the body. The 

 reflex movements, such as those of respiration, remain unimpaired. 

 When an animal thus mutilated is laid on its back, it cannot recover its 

 former posture ; but it moves its limbs, or flutters its wings, and evi- 

 dently is not in a state of stupor. When placed in the erect position, 

 it staggers and falls like a drunken man ; not, however, without making 

 efforts to maintain its balance. Phrenologists, who attribute a different 

 function to the Cerebellum, have attempted to put aside these results, 

 on the ground that the severity of the operation is alone sufficient to 

 produce them ; but, as we shall presently see, many animals may be 

 subjected to a much more severe operation, the removal of the Cerebral 

 hemispheres, without the loss of the power of combining and harmoniz- 

 ing the muscular actions, provided the Cerebellum be left uninjured. 

 Thus, then, the idea of the functions of the Cerebellum, which we derive 

 from Comparative Anatomy, seems fully borne out by the results of ex- 

 periment ; and it is also consistent with the indications which may be 

 drawn from the observations of Pathological phenomena. When the Ce- 

 rebellum is affected with chronic disease, the motor function is seldom 

 destroyed ; but the same kind of want of combining power shows itself, 

 as when the organ has been purposely mutilated. Some kind of lesion 

 of the motor function is invariably to be observed ; whilst the mental 

 powers may or may not be affected, probably according to the influ- 

 ence of the disease in the Cerebellum, upon other parts. The same 

 absence of any direct connexion with the Psychical powers, is shown in 

 the fact, that inflammation of the membranes covering it, if confined to 

 the Cerebellum, does not produce delirium. Sudden effusions of blood 

 into its substance may produce apoplexy or paralysis ; but this may 

 occur as a consequence of effusions into any part of the Encephalon, 

 and does not indicate that the Cerebellum has anything to do with the 

 mental functions, or with the power of the Will over the muscles. 



