The Sense of Hearing 77 



adequate precautions to guard against the action of other 

 than auditory stimuli. 



Zoth (31 p. 170) has pointed out with reason and force 

 that testing the sensitiveness of the mice is especially diffi- 

 cult because of their restlessness. They are almost con- 

 stantly executing quick, jerky movements, starting, stopping, 

 or changing the direction of movement, and it is therefore 

 extremely difficult to tell with even a fair degree of certainty 

 whether a given movement which occurs simultaneously with 

 a sound is a response to the sound or merely coincident with 

 it. With great care in the exclusion of the influence of 

 extraneous stimuli, Zoth tried a large number of experiments 

 to test the hearing of both young and adult dancers. Not 

 once did he observe an indubitable auditory reaction. As he 

 says, "I have performed numerous experiments with the 

 Galton whistle, with a squeaking glass stopper, with caps 

 and cartridges, without being able to come to any certain 

 conclusion. With reference to the Galton whistle and par- 

 ticularly to the tone which was said to have been heard 

 extremely well by Cyon's mice, I believe I am rather safe in 

 asserting that my mice, young (12-13 days) as well as old, 

 do not react to the Konig Galton whistle (7210 Vs.). They 

 could not be awakened out of sleep by repetitions of 

 the sound, nor enticed out of their nests, and their dancing 

 could not be interrupted" (31 p. 170). Zoth's experiments 

 appear to be the most careful and critical of those thus far 

 considered. 



Last to be mentioned, but in many respects of greatest 

 interest and value, is the work of Kishi (21 p. 482) on the 

 problem of hearing. To this acute observer belongs the 

 credit of calling attention emphatically to the ear movements 

 which are exhibited by the dancer. Frequently, as he re- 

 marks, the ears move as if the animal were listening or trying 



