86 BREEDING 



and the hybrid certainly, will, scuttle back into the 

 hind part of the cage, if this is divided off by a parti- 

 tion. The waltzer differs from the ordinary tame 

 mouse in the matter of disposition as much in one 

 direction as the wild mouse or the hybrid does in the 

 other. An albino, if set free, can run away, but does 

 not ; a hybrid or wild mouse, if set free, can run away 

 and does ; but a " waltzer " cannot escape ; it cannot 

 keep up a run in direct line for long, and soon lapses 

 into spinning. 



The cause of the spinning is supposed to be an 

 abnormality in certain organs in close connection 

 with the internal part of the ear. There are three 

 of these semicircular canals, as they are called, in 

 connection with each ear in the normal vertebrate 

 animal, one horizontal and two vertical for each ear, 

 and they are said to be concerned in the normal 

 animal in maintaining the balance of the body. It 

 was formerly stated that the waltzing mouse lacked 

 the horizontal canal in connection with each ear ; 

 but this statement has been proved to be incorrect 

 by the application of a new method of preparing the 

 semicircular canals and of preserving them in their 

 natural state. All six canals are present. But a 

 deficiency in the nerve supply of the semicircular 

 canals is said to have been discovered; and the 

 waltzing habit may be due to this. At any rate, it 

 seems to be generally agreed that this phenomenon 

 of waltzing is determined by some abnormality in 

 the organs which are responsible for preserving the 

 balance of the animal. A physiologist once expressed 



