viii THE HIND-BRAIN 463 



and that in pigeons which had some time previously lost their 

 labyrinth the removal of the cerebellum was followed by incapa- 

 bility of standing, and all other disorders noted when this 

 operation is performed on the normal pigeon. But in a later 

 critical study (1903) Stefani rightly points out that if the 

 phenomena of labyrinthine deficiency can be evoked on de- 

 cerebellated animals, this only shows that this sensory organ 

 influences not merely the cerebellum, but other centres also ; 

 and if the phenomena of cerebellar deficiency appear in animals 

 that have no labyrinth, this means that cerebellar activity is 

 maintained not merely by the impulses coming from the labyrinth, 

 but also by those other multiple afferent paths which anatomy 

 has shown to be directly or indirectly in relation with the 

 cerebellum. 



In order to bring out the special physiological importance of 

 the vestibular nerve, in so far as it is related to the cerebellum 

 and concerned in its functions, Stefani refers to his earlier ex- 

 periments with Weiss (1877), which showed degenerative alteration 

 of Purkinje's cells in the cerebellum of pigeons after destruction of 

 the semicircular canals. Since this result was not confirmed by 

 other observers, Stefani (1899) induced his pupil Deganello to 

 repeat these experiments with the methods of Marchi and Nissl. 

 These new researches not only confirmed the preceding results, 

 but brought out other degenerative changes in the bulb, which 

 are highly interesting for both anatomy and physiology. 



Since Purkinje's cells are the principal element of the cerebellar 

 cortex, a localised degeneration round these in all the lamellae, 

 on one or both sides, as occurs after unilateral lesions < of the 

 labyrinth (according to Stefani and Deganello), can only mean 

 that the activity of the cerebellum is due mainly, if not exclusively, 

 to the impulses transmitted from the labyrinth. 



While fully agreeing with Stefani's facts, we are unable to 

 subscribe to the theory which regards the cerebellum as the organ 

 for equilibration and orientation of the body in relation to its 

 environment. Neither the cerebellum nor the labyrinth, in so far 

 as it is in relation with the cerebellum and influences its activity, 

 has this special function, though undoubtedly both combine with 

 other centres to preserve equilibrium and orientate the body 

 in space. Ewald, who is the most competent authority on the 

 physiology of the labyrinth, expressly admits that the continuous 

 reflex action of the labyrinth on muscular energy and tone is 

 the main function of this organ, and that in virtue of this rein- 

 forcing action (which may oscillate more or less according to the 

 displacement of the centre of gravity of the body) the labyrinth 

 participates in the complex functions of orientation and equilibrium. 



Goltz (1870) held the labyrinth to be the organ for perception 

 of the position of the head, and fundamentally important to 



