162 STATIC FUNCTIONS OF LABYRINTH 



otolith must be shifted to the right, but the reaction of this rotation 

 is elevation of the right eye and depression of the left eye. When 

 pressure is applied directly to the right side of the otolith as in the 

 experiments above described the opposite result is obtained; namely, 

 depression of the right eye and elevation of the left. It must be then 

 that the stimulation does not result from the direct effect of the 

 pressure but from the shifting of the otolith; a displacement to the 

 left is brought about by pressing on its right side under the condi- 

 tions of the experiment, and a similar displacement to the left results 

 from tilting the animal to the left. In other words, it is the displace- 

 ment of the otolith, and not the pressure due to the weight of the 

 otolith, which is the actual stimulus and it is the direction of the dis- 

 placement which determines the direction of the compensatory move- 

 ment in response to the stimulus. 



The experiments described above show that the stimulus arising 

 from the position of the otolith is not due to the pressure as such but 

 to the relative tensions, and is in this particular exactly similar to 

 what I had already found for the ampullae. The stimulus which 

 causes the forced position (static function) is, like the stimulus which 

 causes the compensatory movement (dynamic function), due to rela- 

 tive differences of tension in the organ, rather than to localized stim- 

 ulation of special portions. There is therefore no evidence for a spe- 

 cific difference in the mode of action of the various parts of an ampulla 

 or a macula. The relative tensions appear to determine the propor- 

 tionate nerve excitation for the associated muscle groups in a manner 

 analogous perhaps to the effects of various degrees of tension in the 

 lungs on the vagus endings. I have made no attempt to say just 

 where these differences of tension take effect upon the nerve endings, 

 nor to say what part, if any, the hair cells have in the process. The 

 arrangement of the hair cells would seem admirable for the transmis- 

 sion of the effects of movement or pressure to the nerve endings, but 

 I do not at present see how the matter can be subjected to the test of 

 experiment. 



A part of the experiments on which this paper is based were per- 

 formed at the Scripps Institution for Biological Research. I take 

 great pleasure in acknowledging my obligation to the Director, Pro- 

 fessor W. E. Ritter, for his courtesy in placing the facilities of the 

 Institution at my disposal. 



