FUNCTIONS OF THE CEREBELLUM. 287 



uncles, pons, medulla oblongata, and cord, to the motor nerves, or 

 whether the hemispheral fibres themselves end in this great motorial 

 centre, and thus act, not continuously or directly on the motor nerves, 

 but through this automatic centre, so as to impose upon it definite 

 impressions dictated by the will, is not yet fully decided. But the 

 latter view appears supported by anatomical facts and general con- 

 siderations; and, if this be true, then, even in volitional acts, the 

 actual motor impulse, which immediately excites the muscles, proceeds 

 from the motorial centre, as in the case of any other form of move- 

 ment excited by an idea or an emotion, by a sensori-motor or instinc- 

 tive impulse, or by an excito-motor irritation. 



The office of the corpora striata, in the exercise of voluntary move- 

 ments, may therefore be immediate or direct, as regards the stimulation 

 of the muscles; but the optic thalami may also concur, in an indirect 

 manner, in those movements, by virtue of their function as sensorial 

 centres. It is known that all muscular movements are accompanied 

 by an internal sense of effort to meet resistance, or by a sense of the 

 condition of the muscles concerned; and this sensation or muscular 

 sense, is more or less necessary for the proper guidance of the move- 

 ments. Moreover, other sensations, especially that of sight, are com- 

 monly associated with certain movements of the body, and are some- 

 times their only means of guidance. In complete loss of sensibility in 

 the legs, even though the power of motion remains, the act of walking 

 is impossible, because the guiding muscular sensations are absent; but 

 sometimes the sight may act as a substitute, enabling feeble locomotive 

 efforts to be performed, so long as the person can see his limbs. Even 

 when the sensibility of the skin remains, though the muscles are partly 

 paralyzed, the same difficulty still occurs in using the limbs, unless 

 they are watched by the eyes. A curious case is on record of a nurse, 

 who had lost the muscular sense in one of the upper limbs, and who 

 could only carry a child by constantly watching that limb; as soon as 

 she turned her eyes from it, the limb would fall helpless to her side. 

 (Duchesne.) 



Functions of the Cerebellum. 



The cerebellum is not concerned in the exercise of the psychical 

 functions. Neither does it appear, in any way, to be a seat of the 

 function of common or special sensation. Some, however, refer the 

 so-called muscular sense to certain parts of this organ. When pricked 

 or injured, it does not appear to be sensitive, for no sign of pain re- 

 sults from such irritation. Moreover, when it is completely removed, 

 there is no loss either of common or special sensation in the animal. 

 This organ does not appear to be directly concerned in the mental 

 process of volition, since the will still attempts to exercise itself in an 

 animal deprived of its cerebellum ; for if the animal be then threatened, 

 it will attempt to avoid the blow, or if it be wounded, it will seize the 

 instrument or hand, to try and prevent itself being injured. Lastly, 

 after the removal of the cerebellum, all the instinctive and simple 

 reflex movements, such as those of swallowing, respiration, and others, 

 continue unimpaired. 



