54 The Dancing Mouse 



secondary nature. The primary change is the broad open- 

 ing between the utriculus and the scala tympani from which 

 results the streaming of the endolymph from the semicircular 

 canals into the cochlea. When, as a consequence of the 

 rapid whirling movements, a great part of the endolymph is 

 hurled into the scala tympani, the organ of Corti in the scala 

 vestibuli is fixed and its parts are rendered incapable of 

 vibration. The condition of atrophy which is observable 

 in the sense cells and in the nerve elements is probably due 



Ampulla externa 



Ampulla 



anterior Ranius utriculi 



Membrana 

 basilaris 



Lagena 



Canalis 

 utriculo- 

 saccularis 



Membrana 



Ampulla Macula acustica basilaris 



posterior sacculi 



FIGURE 7. The inner ear of the rabbit. Reproduced from Selenba after 



Retzius. 



to the impossibility of functional activity; it is an atrophy 

 caused by disuse " (25 p. 242). 



To render the terms which occur in this and subsequent 

 descriptions of the ear of the dancer somewhat more intelli- 

 gible to those who are not familiar with the general anatomy 

 of the vertebrate ear, a side view of the inner ear of the rabbit 

 is reproduced from a drawing by Retzius (Figure 7). I have 

 chosen the ear of the rabbit for this purpose, not in preference 



