VIII 



THE HIND-BRAIN 461 



VII. The hypotheses of the functions of the cerebellum have 

 developed in three different directions. The first incorrect ideas 

 of Rolando (1809-28) were modified by Luys, Dalton, and 

 Weir-Mitchell, and after our own prolonged experimental studies 

 assumed a definite form, in which the cerebellum is regarded as an 

 organ of subconscious sensation, which exerts a continuous rein- 

 forcing action upon the other nervous centres, and on which the 

 normal tone of the muscles depends. The theory deduced from 

 the experiments of Flourens (1842), who localised in the cere- 

 bellum the faculty of co-ordinating the movements of posture and 

 locomotion, was most fully set forth by Lussaua (1862), who con- 

 sidered the cerebellum as the centre of muscular sense. Lastly, 

 according to the hypothesis propounded by Magendie (1825) solely 

 on the strength of the forced movements of rotation and retro- 

 pulsion after lateral lesions or symmetrical destruction of the 

 cerebellar substance, the cerebellum is an organ for maintaining 

 the equilibrium of the body in the erect posture and in walking. I 

 This hypothesis was further developed in the work of Terrier (1876), 

 Bechterew (1884-96), Thomas (1897), Stefani (1887-1903), and 

 others, who promulgated various conceptions of the intervention 

 of the cerebellum, in the equilibration and orientation of the body 

 in space. 



Investigation of this last theory is especially important, because 

 it leads to the discussion of the physiological relations between 

 the cerebellum and the labyrinth, the peripheral sense-organ 

 served by the vestibular nerve, which we have seen to be connected 

 with the cerebellum by means of the nucleus of Deiters. 



This is not the place to discuss the complex physiological 

 doctrine of the end-organs of the vestibular nerve, or labyrinth, 

 which must be dealt with along with the other sense-organs. It 

 has been experimentally demonstrated that the nerve-endings of 

 the semicircular canals and saccules of the vestibulum constitute 

 an extremely delicate organ of sense, necessary to the preservation 

 of equilibrium and the orientation of the body in space. Here we 

 need only insist on the fact which is of predominant importance 

 for the physiology of the cerebellum, that the proximal and 

 remote phenomena consequent on unilateral and bilateral destruc- 

 tion of the labyrinth resemble in no slight degree those which 

 appear after the unilateral or bilateral ablation of the cerebellum. 



Flourens, who was the first to propound a theory of the 

 function of the labyrinth (1824-30), recognised the analogy between 

 the motor disorders consequent on lesions of the semicircular 

 canals and those which follow cerebellar ablations. The further 

 investigations of Goltz (1869-79) confirmed and extended the 

 likeness between the effects of the two operations. Lastly, Ewald 

 (1887, 1889-92), who investigated the more remote residual 

 phenomena due to uni- and bi-lateral ablation of the labyrinth, 



