350 DYNAMIC FUNCTIONS OF LABYRINTH 



affecting the compensatory movements or the functions of equilibra- 

 tion, and Ewald^ stated that in the pigeon, after the canals had been 

 Hgatured, plugged, and cut, compensatory movements of the eyeballs 

 and eye nystagmus were produced by rotation. 



These experiments show that the canals are not necessary to the 

 dynamic functions. Certain objections, however, might be raised. 

 Loeb does not state specifically that all the canals were cut. Since I 

 have shown that all the dynamic functions except that of response to 

 rotation in a horizontal plane may be performed by an ear from which 

 all the ampullae have been removed, it would be necessary to know 

 that the horizontal canals had been cut before the proof could be con- 

 sidered complete. Furthermore, in the dogfish each horizontal am- 

 pulla reacts to rotations in one direction only ; this according to Ewald 

 is not the case in the pigeon but his proof also is incomplete. 



Since in the dogfish the response to horizontal rotation is brought 

 about by the horizontal ampulla only, it would be a crucial experi- 

 ment artificially to change the plane of this canal with reference to 

 the skull of the animal and see whether this change does or does not 

 alter the response to rotation. I have succeeded in doing this by the 

 following method. 



The right horizontal canal was laid bare for nearly the whole dis- 

 tance from its ampulla to the point where its posterior end reenters 

 the vestibule. It was then ligatured and cut as far posterior as pos- 

 sible and the cut end was gently lifted into a vertical position, laid over 

 against the skull, and supported there by a pledget of cotton. Its new 

 plane was at right angles to its original plane and also at right angles 

 to the long axis of the body. It is needless to say that in this opera- 

 tion extreme care must be taken not to exert the least traction on the 

 ampulla. It is clear that with the canal in the new position rotation 

 of the animal in a horizontal plane, that is around a dor so ventral axis, 

 could not even theoretically give rise to a current in the canal. On 

 rotation to the right, however, the eyes turn to the left and on rota- 

 tion to the left the eyes turn to the right; that is, the ampulla whose 

 canal is now at right angles to its normal position acts just like the 



^ Ewald, J. R., Physiologische Untersuchungen uber das Endorgan des Nervus 

 octavus, Wiesbaden, 1892. 



