46 The Dancing Mouse 



surface, that they are timid ; but this is due probably to the 

 uncomfortable and unusual position rather than to percep- 

 tion of their distance from the ground. That they lack 

 visual dizziness seems fairly well established. 



When rotated in a cyclostat l the dancer, unlike the com- 

 mon mouse, does not exhibit symptoms of dizziness. The 

 following vivid description of the behavior of both kinds of 

 mice when rotated is given by Alexander and Kreidl (i p. 548). 

 I have not verified their observations. 



The common mouse at first runs with increasing rapidity, 

 as the speed of rotation of the cyclostat cylinder is increased, 

 in the direction opposite to that of the cylinder itself. This 

 continues until the speed of rotation has increased to about 

 60 revolutions per minute. As the rotation becomes still 

 more rapid the mouse begins to crawl along the floor, its 

 body stretched out and clinging to the floor. At a speed of 

 250 revolutions per minute it lies flat on the floor with its 

 limbs extended obliquely to the movement of rotation, and 

 at times with its back bent against the axis of the cylinder; 

 in this position it makes but few and feeble efforts to crawl 

 forward. When the rotation is suddenly stopped, the animal 

 pulls itself together, remains for some seconds with extended 

 limbs lying on the floor, and then suddenly falls into convul- 

 sions and trembles violently. After several attacks of this 

 kind, cramps appear and, despite its resistance, the animal 

 is thrown about, even into the air at times, as if by an external 

 force. This picture of the position assumed during rapid 

 rotation, and of cramps after the cessation of rotation (the 

 typical picture of rotation dizziness), is repeated with great 

 uniformity in the case of the common mouse. Within fif- 

 teen minutes after being returned to its cage the animal re- 



1 An apparatus consisting of a glass cylinder with a mechanism for turn- 

 ing it steadily and at different speeds about its vertical axis. 



