n 9 8 THE EAR. 



Flourens, in 1828, announced that injury to the semicircular canals 

 causes motor inco-ordination and disturbance of equilibrium, and that sec- 

 tion of the canals produces a rotatory movement of a kind corresponding 

 to the canal that had been divided ; in other words, that division of a 

 membranous canal causes rotatory movements round an axis at right 

 angles to the plane of the divided canal ; that is to say, the body of the 

 animal always moves in the direction of the cut canal. Further, he was 

 led to suggest that, as section of the canals produces disturbances of the 

 same kind as those following injury of the cerebellum, they also have to 

 do with co-ordination of movement. 



These observations of Flourens have been corroborated by many 

 other observers. Vulpian l thought that the phenomena are due to an 

 auditive vertigo, which acts on all the organs. Brown-Sequard stated 

 that the same phenomena are caused by irritation of the auditory nerve, 

 but this was denied by Schiff. 2 In 1869, Lowenberg, 3 after numerous 

 experiments, more especially on the horizontal and vertical canals, 

 in which they were not only divided but subjected to mechanical and 

 chemical excitation, concluded that the difficulties of co-ordination of 

 movement are due, not to paralysis, but to excitation, that these move- 

 ments are reflex and unconscious, and that the centres for the reflex 

 excitations are in the optic lobes (bird). 



An important contribution was made to the subject by Goltz, 4 who, 

 although he devised no new experiments of importance, and relied 

 mainly on the observations of Flourens, was the first to clearly for- 

 mulate the conditions necessary for co-ordination, namely — (1) A central 

 co-ordinating organ, (2) centripetal fibres with their peripheral termina- 

 tions, and (3) centrifugal fibres with their terminal organs. A lesion of 

 any one of these portions of the mechanism produces inco-ordination. 

 Goltz admitted the contention of Flourens, that the canals are 

 necessary for the equilibration of the body, but he went farther, and 

 contended that they have mainly to do with the equilibrium of the head. 

 The mechanism was stated to be as follows : — The endolymph exercises 

 a stronger pressure on the walls of the ampullae when the movements 

 of the head bring these to a low level ; this pressure irritates the nerves 

 of the ampulke and excites centripetal impulses, which reflexly cause 

 movements resulting in the equilibration of the head. If, then, the 

 canals are divided or injured, disordered movements ensue from the 

 head losing equilibrium. This theory is often termed the hydrostatic 

 theory of Goltz, and it assumes that the movements of the body are 

 regulated entirely by the more or less conscious appreciation we have 

 of the position of the head in space. 



The subject was next investigated by Cyon, 5 who found the general 

 loss of co-ordination of movement after section of a canal to be 

 due to the disordered movements of the head. Thus, when the head of 

 a pigeon was fixed so that the beak was directed upwards and the 



1 " Lecons sur la physiologie du systeme nerveux," Paris, 1866, p. 600. 



2 "Leiirbuch der Physiologie," 1858. 



3 Arch. f. Augcn- u. Ohrenh., Bd. iii. 



4 Arch. f. d. <jcs. Physiol., Bonn, Bd. iii. S. 172. 



5 Ibid., 1873, Bd. viii. ; " Cours de physiologie," St. Petersbourg, 1873-74, tome ii. ; 

 " MethodikderphysiologischenExperimente,"St. Petersburg, 1876, S. 540-547 ; "Rapports 

 physiologiqu.es entre le nerf acoustique, " etc., Compt. rend. Acad. d. sc, Paris, 1876, tome 

 lxxxii. p. 856 ; "Les organes pt$ripht5riques du sens de l'espace," ibid., Paris, 1877, tome 

 lxxxv. p. 1284; also " Recherches experimentales sur les fonctions des canaux semi- 

 circulaires, " These, 1878. 



