FUNCTIONS OF THE CEREBELLUM. 711 



produces any thing resembling the results of cerebellar injury. Certain important coordi- 

 nate muscular movements are well known to be dependent upon distinct nerve-centres. 

 The acts of respiration are presided over exclusively by the medulla oblongata. Deglutition 

 probably has its distinct nerve-centre, as well as the movements of the eyes. The centre 

 regulating the coordinate movements in speech is situated in the anterior cerebral lobes. 

 None of these peculiar movements are affected by extirpation of the cerebellum. 



If there be a distinct nerve-centre which presides over the coordination of the general 

 voluntary movements, experiments upon the higher classes of animals show that this 

 centre is situated in the cerebellum. It may be either in the entire cerebellum or in a 

 certain portion of this organ, but, if it be confined to a restricted part, this has not yet 

 been determined. If the cerebellum preside over coordination, as a physiological neces- 

 sity, the centre must be connected by nerves with the general muscular system. If this 

 connection exist, a complete interruption of the avenue of communication between the 

 cerebellum and the muscles, we should naturally expect, would be followed by loss of 

 coordinating power. From the anatomical connections of the cerebellum, it appears that 

 the only communication between this organ and the general system is through the pos- 

 terior white columns of the spinal cord. We have seen that these columns are not for 

 the transmission of the general sensory impressions, and there is no satisfactory evidence 

 that they convey to the encephalon the so-called muscular sense. As regards general 

 sensibility and voluntary motion, we cannot ascribe any function to the posterior white 

 columns, except that, when they are divided at several points, we invariably have want 

 of coordination of the general muscular system. When the posterior white columns are 

 disorganized in the human subject, we have loss or impairment of coordinating power, even 

 though the general sensibility be not affected, as in the disease called locomotor ataxia. 



Confining ourselves still to the interpretation of experiments upon living animals, and 

 leaving for subsequent consideration the phenomena observed in cases of disease or injury 

 of the cerebellum in the human subject, we are led to the following conclusions : 



There is a necessity for coordination of the movements of the general voluntary system 

 of muscles, by means of a nerve-centre or centres. 



"Whatever other functions the cerebellum may have, it acts as the centre presiding 

 over equilibration and general muscular coordination. 



The cerebellum has its nervous connections with the general muscular system through 

 the posterior white columns of the spinal cord, a fact which is capable both of anatomical 

 and physiological demonstration. 



If the cerebellum be extirpated, there is loss of coordinating power ; and, if the pos- 

 terior white columns of the cord be completely divided, destroying the communication 

 between the cerebellum and the general system, there is also loss of coordinating power. 



When a small portion only of the cerebellum is removed, there is slight disturbance 

 of coordination, and the disordered movements are marked in proportion to the extent 

 of injury to the cerebellum. 



After extirpation of even one-half or two-thirds of the cerebellum, the disturbances in 

 coordination immediately following the operation may disappear, and the animal may 

 entirely recover, without any regeneration of the extirpated nerve-substance. This im- 

 portant fact enables us to understand how, in certain cases of disease of the cerebellum in 

 the human subject, when the disorganization of the nerve-tissue is slow and gradual, there 

 may never be any disorder in the movements. 



We present the above conclusions, as in our own mind positive and definite. It i- 

 proper to state, however, that the definition of the function of the ren-hellum is one of 

 the points stated by many physiological authors as doubtful and unsettled ; and this Ifl 

 mainly because some writers have been unable to harmonize the experimental facts ;r 

 detailed, with cases of disease or injury of the cerebellum in the human subject. We 

 conceive that this has frequently been due to an imperfect study of the pathological facts, 

 which we now propose to discuss. 



