118 PHYSIOLOGY CHAP. 



whether these are or are not due to sound-waves. But the otoliths 

 lie in the saccules of the vestibule, not in the canals, and if it be 

 admitted that these oscillations and those of the eiidolymph can 

 stimulate the canals, or that these oscillations are in relation with 

 the position of the head, then Cyon's theory merges into that of 

 Goltz ; or if this be not admitted, then we cannot see how these 

 oscillations can give information as to the position of the head. 



From the physiological standpoint the spatial sense of Cyon 

 and the sense of equilibrium of Goltz are analogous in significance. 



Nevertheless it was Cyon who demonstrated the effect of 

 artificial stimulation of the canals upon the movements of the 

 eyes. Flourens, too, noted movements of the eyeball after section 

 of the canals in rabbits, but, according to his observations, these 

 movements ceased when the head became fixed, and must there- 

 fore be regarded as compensatory acts, associated with the head 

 movements. Cyon, on the contrary, -showed that the nystag- 

 mus of the eyes in rabbits did not cease when the head became 

 stationary, but increased ; and further showed that strabismus 

 and nystagmus were produced in rabbits by direct stimulation 

 of the canals with the induced current, and, like the movements 

 of the head, occur in different directions, according to the canal 

 stimulated. 



Neither we ourselves nor Stefani, who is a competent judge, 

 have been able to see the physiological importance of Cyon's 

 later experiments. His conclusions from dancing mice have, 

 moreover, not been confirmed by other experimenters. 



The theory of Goltz was taken up and defended in different 

 forms by a number of other authors. Purkinje (1820) had shown, 

 in his studies on vertigo, that passive rotation of the whole body 

 round its long axis produced a definite sensation (independent of 

 the visual sensations) of rotatory movements in different directions, 

 according to the plane of rotation and the position of the head. 

 He also produced the same sensation by passing a constant current 

 through the head. Purkinje supposed that the rotatory vertigo 

 and galvanic vertigo were produced through the cerebellum, and 

 were excited by the movements of the circulating fluids caused 

 by rotation, and by the anaemia and hyperaemia produced by the 

 galvanic current. 



After Goltz published his theory Breuer (1875-76), and almost 

 simultaneously Mach and Crum Brown, repeated the old experi- 

 ments of Purkinje with a view to finding a more adequate inter- 

 pretation of the phenomena described by Flourens and Goltz. 



Mach found that if the subject of experiment is seated on a 

 stool fixed to a platform that can be rotated round a vertical 

 axis at a known distance from the axis, and is turned round with 

 his eyes blinded and his head in the normal position, he is dis- 

 tinctly aware of the rotation in the horizontal direction to right 



