The Sense of Hearing 79 



the results obtained with mice from one to twenty-eight days 

 old. 



My preliminary tests were made with noises. While care- 

 fully guarding against the interference of visual, tactual, 

 temperature, and olfactory stimuli, I produced noises of vary- 

 ing degrees of loudness by clapping the hands together 

 suddenly, by shouting, whistling, exploding pistol caps, 

 striking steel bars, ringing an electric bell, and causing an- 

 other mouse to squeak. To these sounds a common mouse 

 usually responds either by starting violently, or by trem- 

 bling and remaining perfectly quiet for a few seconds, as 

 if frightened. The adult dancers which I have tested, and 

 I have repeated the experiment scores of times during the 

 last three years with more than a hundred different indi- 

 viduals, have never given unmistakable evidence of hearing. 

 Either they are totally deaf or there is a most surprising lack 

 of motor reactions. 



Precisely the same results were obtained in tests made 

 with the Galton whistle throughout its range of pitches, and 

 with Appuun whistles which, according to their markings, 

 ranged from 2000 Vs. (C 4 ) to 48,000 (G 9 ), but which un- 

 doubtedly did not correspond at all exactly to this range, and 

 with a series of Konig tuning forks which gave tones vary- 

 ing in pitch from 1024 to 16,382 complete vibrations. 



I am willing to trust these experimental results the more 

 fully because during all the time I have had adult dancers 

 under observation I have never once seen a reaction which 

 could with any fair degree of certainty be referred to an 

 auditory stimulus. Never once, although I have tried re- 

 peatedly, have I succeeded in arousing a dancer from sleep 

 by producing noises or tones, nor have I ever been able to 

 observe any influence of sounds on the dance movements. 

 All of Cyon's signs have failed with my mice. Occasionally 



