122 PHYSIOLOGY CHAP. 



the whole of the phenomena consequent on partial or total uiii- or 

 bilateral lesion in the end-organ of the eighth nerve, and by his 

 ingenious methods brought to light certain facts that had escaped 

 his predecessors, including his own master, Goltz. These are the 

 more remote residual effects of labyrinthine deficiency and consist 

 in the abnormal relaxation of inactive muscles (muscular atony), 

 the diminished energy displayed during activity (asthenia), and 

 the defective precision of the movements which they execute 

 (astasia). Ewald also claims that muscular sensibility is diminished 

 in the dog that has lost its labyrinth, but this is less a fact than 

 an interpretation of the observation that the animal draws back 

 its paw more slowly if the support beneath it is taken away, which 

 may be due to the atonia and asthenia of the muscles. 



There is accordingly no sharp line of demarcation between the 

 phenomena described by Goltz and those observed by Ewald : both 

 have the same origin. Moreover, it is clear that removal of the 

 labyrinth on one or both sides produces effects that are approxi- 

 mately identical with those we have already described at length, 

 after removal of half or the whole cerebellum. The duration of 

 the effects of lesions of the labyrinth is, however, less than those 

 of cerebellar ablation. According to Ewald, the disturbances due 

 to the destruction of one labyrinth disappear after a week, of both 

 after about a month. 



In Chapter VIII. of the last volume it was shown, particularly 

 from the work of Stefani and Deganello, that the twigs of the 

 vestibular nerve, which innervate the cristae of the ampullae and 

 the maculae of the vestibular saccules, are in close anatomical 

 relation with the hind-brain, i.e. with the cerebellum and bulb, 

 and that the experimental facts set out by Ewald, Stefani, and 

 Deganello as a whole support the conclusion that these parts of 

 the brain represent the most immediate centres of the vestibular 

 division of the eighth nerve. Our task is therefore only to bring 

 into relation with the functions of the cerebellum the most 

 probable theories that have been propounded in regard to the 

 functions of the vestibular organs. 



Ewald, in agreement with Breuer, Mach, and Crum Brown, 

 assumes that the labyrinth can be excited mechanically by active 

 and passive movements, rectilinear or angular; but in order to 

 explain the atonic, asthenic, and astatic effects which he has shown 

 with so much operative skill, he further assumes that the nerve- 

 organs of the labyrinth are in tonic excitation during the waking 

 state, which reflexly determines the tone of the striated muscles, on 

 which their normal functions depend. 



Ewald's theory of labyrinthine tone harmonises perfectly with 

 our own theory of cerebellar tone. It explains the certainty of 

 equilibrium of the body in standing and walking, the promptness 

 with which equilibrium is regained by compensatory movements 





