I 



THE ABLATION OF THE CEREBELLUM 711 



and nucleus globosus of the cerebellum . In this way, this organ is brought into rela- 

 tion with the semicircular canals of the internal ear. It also receives a few fibers 

 from the trigeminus, vagus and accessory nerves. The efferent fibers of the in- 

 ferior peduncle arise in the dentate nucleus and form the direct anterolateral bundle 

 which connects with the spinal tracts. 



The Ablation of the Cerebellum. — The size and complexity of the 

 cerebellum differ greatly in different animals. It reaches its highest 

 development in the apes and man. In these animals we also find the 

 greatest relative development of the cerebrum, although these organs 

 do not display a perfect structural correspondence. We have seen 

 that the cerebral cortex is made up of complexes of neurons which show 

 very decided differences in their structure and arrangement, and medi- 

 ate different nervous processes. The cerebrum, therefore, presents 

 unmistakable evidence of a division of function. A precise locahza- 

 tion of this kind is not in evidence in the cerebellum. On the contrary, 

 this organ exhibits a decidedly homogeneous structure, and hence, we 

 cannot go wrong in assuming that it possesses a single specific func- 

 tion. The correctness of this conclusion will become more apparent 

 later on. 



While repeated attempts have been made by Rolando (1809), 

 Flourens (1824), Magendie (1825), Vulpian (1866), Nothnagel (1876), 

 and others, to apply to the cerebellum the methods previously used 

 in experiments upon the cerebrum, the results have proved very 

 unsatisfactory on account of the difficulties which surgical interferences 

 with this organ must necessarily be confronted by. Subsequent to 

 the time of Galvani and Volta, when an undue stress was placed 

 upon the electrical phenomena in nature, it was believed that the 

 cerebellum supplies the ''nerve force" which is required for our bodily 

 processes. No doubt, this now ridiculous contention was based chiefly 

 upon the observation that the lamellated outline of this organ in cross- 

 section presents certain characteristics which remind one of the Vol- 

 taic pile. Later on Gall advocated the hypothesis that it is concerned 

 with the sexual emotions. The first tangible view of its function was 

 presented by Flourens, who regarded it as an organ for the coordination 

 of muscular movements and particularly of those concerned in locomo- 

 tion and the preservation of the equilibrium. 



This view is widely accepted to-day and finds its origin in the array 

 of S5nnptoms "displayed by pigeons whose cerebellar hemispheres 

 have been removed either in part or in their entirety. Birds, in par- 

 ticular, are closely dependent upon a properly balanced muscular 

 apparatus, inclusive of its central coordinating mechanism, the cere- 

 bellum. It may be inferred, therefore, that the excessive development 

 of this organ noted in these animals, is in keeping with their muscular 

 power, and that its removal must give rise to especially disturbing 

 symptoms. Thus we find that a pigeon deprived of its cerebellar 

 hemispheres, shows a spasdic position of the wings, legs and head which 

 renders standing, walking and flying impossible. Any attempt to 



