CHAPTER V 



STRUCTURAL PECULIARITIES AND BEHAVIOR 



THE activities of an animal are expressions of changes 

 which occur in its structure, and they can be explained satis- 

 factorily only when the facts of structure are known. Such 

 peculiarities of activity as are exhibited by the dancing 

 mouse, as contrasted with the common mouse, suggest 

 at once that this creature has a body which differs in 

 important respects from that of the ordinary mouse. In 

 this chapter I shall present what is known concerning the 

 structural bases for the whirling, the lack of equilibrational 

 ability and of dizziness, the quick jerky head movements, 

 the restlessness, and the partial or total deafness of the 

 dancing mouse. 



Comparative physiologists have discovered that the ability 

 of animals to regulate the position of the body with respect to 

 external objects and to respond to sounds is dependent in 

 large measure upon the groups of sense organs which collec- 

 tively are called the ear. Hence, with reason, investigators 

 who sought structural facts with which to explain the forms 

 of behavior characteristic of the dancer turned their atten- 

 tion first of all Jto the study of the ear. But the ear of the ani- 

 mal is not, as might be supposed on superficial examination, a 

 perfectly satisfactory natural experiment on the functions of this 

 group of sensory structures, for it is extremely uncertain whether 

 any one of the usual functions of the organ is totally lacking. 

 Dizziness may be lacking, and in the adult hearing also, but 



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