LABYRINTH AND EQUILIBRIUM. 

 XL The Mechanism of the Dynamic Functions of the Labyrinth. 



By S. S. maxwell. 



{From the Rudolph Spreckels Physiological Laboratory, University of California, 

 Berkeley, and the Marine Biological Laboratory, Woods Hole.) 



(Received for publication, January 23, 1920.) 



In a previous paper,i I have shown that the ampullae alone, without 

 the otoliths, suffice for all the dynamic functions of equilibrium of the 

 ear, and that the otoliths alone, without the ampullae, also suffice for 

 all the dynamic functions except that of response to rotation in a 

 horizontal plane. I wish now to point out what I believe to be the 

 mechanisms by which these reactions are brought about. 



The Dynamic Functions of the AmpuUce. 



Mach, Brown, and Breuer at first attached paramount importance 

 to the space relations of the semicircular canals. It was assumed 

 that rotation of the head in the plane of a canal caused, by the inertia 

 of the endolymph, a current within the canal contrary to the direction 

 of rotation. It was supposed that the hair cells of the crista were 

 deflected by the current and stimulation of the nerve endings resulted. 

 Mach,2 however, very soon saw that under the conditions existing 

 in the labyrinth such a current could not be produced, and Breuer 

 later admitted that the hair cells do not project into the endolymph 

 but are covered by a gelatinous mass. 



On the experimental side, Loeb^ found that in the dogfish the canals 

 could be cut through and even large portions could be excised without 



^ Maxwell, S. S., Labyrinth and equilibrium. I. A comparison of the eflfect of 

 removal of the otolith organs and of the semicircular canals, J. Gen. Physiol., 

 1919-20, ii, 123. 



^ Mach, E., Grundlinien der Lehre von den Bewegungsempfindungen, Leipsic, 

 1875. 



' Loeb, J., Ueber Geotropismus bei Thieren, Arch. ges. Physiol., 1891, xlix, 175. 



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