FUNCTIONS OF THE CEREBELLUM. 353 



co-ordination. And in the Bird, the number of muscles employed in the 

 movements of flight, and in directing the course of these, is really comparatively 

 small ; as may at once be perceived, by comparing the rigidity of the skeleton 

 of the trunk of the Bird with that of Man, and by remembering the complete 

 inactivity of the lower extremities during the active condition of the upper. 

 In fact, the motions of the wings are so simple and regular, as to suggest the 

 idea, that, as in Insects, their character is more reflex than directly voluntary : 

 an idea which is supported by the length of time during which they can be 

 kept up without apparent fatigue, and also by the important facts already men- 

 tioned, which experimental research has disclosed ( 435). It is seen, then, 

 that Comparative Anatomy fully confirms the idea, which Experimental physi- 

 ology suggests, respecting the chief functions of the Cerebellum. 



463. Some of Magendie's experiments indicate a further connection of 

 this organ with the motor function, the nature of which is still obscure. This 

 physiologist asserts that, if a wound be inflicted on the Cerebellum, the animal 

 seems compelled by an inward force 'to retrograde movement, although mak- 

 ing an effort to advance; and that, if the Crus Cerebelli on one side be injured, 

 the animal is caused to roll over towards the same side. Sometimes (if Ma- 

 gendie's statements can be relied on), the animals make sixty revolutions in a 

 minute, and continued this movement for a week without cessation. Division 

 of the second Crus Cerebelli restored the equilibrium. Hertwig observed the 

 same phenomenon, when the Pons Varolii (which is nothing more than the 

 commissure of the Cerebellum, surrounding the Crura Cerebri) was injured on 

 one side ; and he has also remarked, that the movements of the eyes were no 

 longer consensual. 



464. On turning to Pathology for evidence of the functions of the Cerebel- 

 lum, we meet with much that seems contradictory. It must be remembered 

 that a sudden effusion of blood, even to a small extent, in any part of the En- 

 cephalon, is liable to produce the phenomena of apoplexy or paralysis ; and 

 inferences founded upon the phenomena exhibited after sudden lesions of this 

 description are, therefore, much less valid, than those based on the results of 

 more chronic affections. In regard to these last, however, it is to be observed, 

 that we are not yet in a condition to be able to state with precision, what 

 amount of morbid alteration in any part of the nervous centres, is compatible 

 with but slightly-disturbed performance of its function ; and that cases are 

 every now and then occurring, which would upset all our previous notions, if 

 we were not aware, that the same difficulty presents itself, even in regard to 

 the best-established results in Neurology. It is also to be remembered, that 

 the results of disease, occasioning pressure, will be peculiarly liable to affect 

 the Medulla oblongata, as well as the Cerebellum ; and will thus occasion a 

 greater loss of motor power than would be occasioned by the mere suspension 

 of the function of the latter. 



465. Pathological phenomena, when examined with these reservations, 

 appear to coincide with the results of experiment, in supporting the conclu- 

 sion, that the Cerebellum is not in any way the instrument of psychical ope- 

 rations. Inflammation of the membranes covering it, if confined to that part, 

 does not produce delirium ; and its almost complete destruction by gradual 

 softening, does not appear necessarily to involve loss of intellectual power. 

 "But," remarks Andral, " whilst the changes of intelligence were variable, 

 inconstant, and of little importance, the lesions of motion, on the contrary, 

 were observed in all the cases [of softening which had come under his no- 

 tice] except one ; and in this it is not quite certain that motion was not inter- 

 fered with." In general, apoplexy of the Cerebellum is accompanied by para- 

 lysis ; but this is by no means usual in cases of chronic disease, in which 

 there is rather an irregularity of movement, with a degree of restlessness re- 



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