48 The Dancing Mouse 



whose semicircular canals have been destroyed. They per- 

 form violent forced movements, turn somersaults forward 

 and backward, run up inclines and fall over the edges, and 

 roll over and over. In a word, they show precisely the kind 

 of disturbances of behavior which are characteristic of ani- 

 mals whose semicircular canals are not functioning nor- 

 mally. Cyon, however, observed that in certain dancers 

 these peculiarities of behavior did not appear when they 

 were blinded, but that, instead, the animals gave no other 

 indication of being inconvenienced by the lack of sight than 

 do common white mice. This matter of individual differences 

 we shall have to consider more fully later. 



No other observer agrees with Cyon in his conclusions 

 concerning vision, or, for that matter, in his statements con- 

 cerning the behavior of the blind dancer. Alexander and 

 Kreidl (i p. 550) contrast in the following respects the behavior 

 of the white mouse and that of the dancer when they are 

 blinded. The white mouse runs less securely and avoids 

 obstacles less certainly when deprived of vision. The dancer 

 is much disturbed at first by the shock caused by the removal 

 of its eyes, or in case they are covered, by the presence of 

 the unusual obstruction. It soon recovers sufficiently to 

 become active, but it staggers, swerves often from side to 

 side, and frequently falls over. It moves clumsily and more 

 slowly than usual. Later these early indications of blindness 

 may wholly disappear, and only a slightly impaired ability 

 to avoid obstacles remains. 



It was noted by Kishi (21 p. 484) that the dancer when 

 first blinded trembles violently, jumps about wildly, and rolls 

 over repeatedly, as Cyon has stated ; but Kishi believes that 

 these disturbances of behavior are temporary effects of the 

 strong stimulation of certain reflex centers in the nervous 

 system. After having been blinded for only a few minutes 



