84 The Dancing Mouse 



definiteness of the negative results obtained with No. 4 and 

 partly because of the cruelty of subjecting an animal to dis- 

 agreeable conditions which it is unable to avoid, the experi- 

 ment was not repeated with other individuals. I have never 

 conducted an experiment which gave me as much discomfort 

 as this ; it was like being set to whip a deaf child because it 

 did not learn to respond to stimuli which it could not feel. 



By a very similar method No. 18 was tested for his sen- 

 sitiveness to the noise and jar from the induction apparatus 

 which was used in connection with many of my experiments 

 on vision and the modifiability of behavior. In this experi- 

 ment the wrong box was indicated by the buzzing sound of 

 the apparatus and the slight vibrations which resulted from 

 it. Although No. 18 was tested, as was No. 4, for ten suc- 

 cessive days, ten trials each day, it gave no evidence of 

 ability to avoid the box-which-buzzed. 



Since both direct and indirect methods of testing the hear- 

 ing of the dancer have uniformly given negative results, in 

 the case of mice more than five weeks old, I feel justified in 

 concluding that they are totally deaf and not merely irre- 

 sponsive to sounds. 



Rawitz's statements, and the fact that what may have 

 been auditory reactions were obtained with a few individuals 

 of five weeks of age, suggest that the mice may be able to 

 hear at certain periods of life. To discover whether this is 

 true I have tested the young of twenty different litters from 

 the first day to the twenty-eighth, either daily or at intervals 

 of two or three days. In these tests Konig forks, steel bars, 

 and a Galton whistle were used. The results obtained are 

 curiously interesting. 



During the first two weeks of life none of the mice which 

 I tested gave any visible motor response to the various sounds 

 used. During the third week certain of the individuals re- 



