MECHANICS OF THE INNER EAR 



density throughout at any given time, that is practically, as 

 unelastic, incompressible. 



Fig. i. The external and the middle ear 



The walls of the tube consist of hard, unyielding bone, 

 except in two places where the bone is broken through and 

 the openings closed by flexible mem- 

 The tube has branes. These two places are common- 



two windows to '. v called the oval and the round windows, 

 communicate with (The fact that the tube communicates 

 the middle ear with the semicircular canals and the oth- 



er parts of the labyrinth can here be neg- 

 lected, since all these communicating cavities are also enclos- 

 ed in bone, not possessing any windows.) On the other side 

 of these windows there is the air of the middle ear. Let us 

 now consider at once what could happen to the fluid in the 

 tube if rhythmical changes of pressure in the external air (a 

 "tone") caused, through the tympanum, like changes (of 

 condensation and rarefaction) in the air of the middle ear. 

 Let us at present, however, consider this under the imaginary 

 assumption of no chain of ossicles existing in the middle ear. 

 What was said about waves in the fluid of the tube holds 

 good to some extent also for the air in the middle ear. That which 

 occurs there is the same as that which occurs, say, in a bicycle 



