THE SENSE OF MOVEMENT DYNAMIC SENSE 789 



been blocked. Konig and Brener^ have obtained very similar results 

 by painting the ampulla with cocain so as to paralyze the nerve- 

 endings. These data serve to contradict the view sometimes advocated, 

 that the disorders following lesions of the semicircular canals, are phe- 

 nomena of stimulation rather than of abolition of function (Ausfalls- 

 erscheinungen) . Besides, of course, we are in possession of the fact 

 that these disorders are generally lasting in character. ^ Ewald has 

 also stimulated the membranous canal by pressing upon it with a 

 bristle inserted through an opening in the bony canal, and by blowing 

 a current of air upon it through a narrow tube. In another set of 

 experiments the endolymph was made to circulate by this means first 

 in one direction and then in the other. In the dog-fish, Lee^ has found 

 that pressure upon any particular ampulla gives rise to movements 

 of those fins which this animal ordinarily employs in moving in the 

 plane of the canal stimulated. Electrical stimulation of the canals 

 has been resorted to by Brener. It gives rise to the so-called galvano- 

 tropic reaction, consisting in a deviation of the head toward the anode. 

 All these procedures have fully confirmed the theory of Brener and 

 Mach which holds that the specific stimulant of the sensory epithelium 

 of the ampulla is the movement of the endolymph. Besides, it has 

 been made evident that these canals evoke movements only along par- 

 ticular planes of the body. 



Labyrinthine Reflexes and Tonus. — The sensations of movement 

 with which we are concerned at the present time are, of course, passive 

 in their nature and enable us to form judgments regarding movements 

 along straight and curved lines. These purely labyrinthine impres- 

 sions, however, are supplemented by others received from the retinae, 

 the cutaneous receptors, and the proprioceptors proper. It cannot 

 surprise us, therefore, to find that this relationship is sometimes re- 

 versed, so that the labyrinthine sensations become associated with 

 compensatory reactions of different kinds. Chief among these are 

 movements of the eyes and head. If a frog is placed upon a board and 

 is slightly moved around its transverse axis, it raises and lowers its 

 head against the direction of this movement. In a similar way, if 

 rotated upon a horizontal disc, it bends its body against the direction 

 of the rotation. These compensatory reactions cease immediately 

 if the labyrinth is destroyed or if the nerve fibers leading from it are 

 cut. Equally pronounced effects may be obtained in the fish,^ birds 

 and mammals. Since these compensatory movements may also be 

 evoked in the blind and are, therefore, entirely independent of visual 

 sensations, their labyrinthine origin cannot be doubted. 



As has been pointed out by Purkinje, Ewald and Stein, ^ any 



1 Sitzungsber., Akad. zu Wien, cxii, 1887, 1903. 



2 Gaglio, Archiv ital. de biologie, xxxi, 1899, 377. 



3 Jour, of Physiol., xvii, 1895, 192. 



4 Loeb, Pfluger's Archiv, xHx, 1891, 175. 

 6 Zentralbl. fur Physiol., xiv, 1900, 222. 



