MECHANICS OF THE INNER EAR 7 



ments of the stirrup, and consequently in movements of the 

 fluid in the tube. If the tympanum is destroyed to such an 

 extent that the middle ear can no longer act even imperfectly 

 as a drum, movements of the fluid in the tube must be dif- 

 ficult to produce. The organ is then deprived of its normal 

 manner of functioning — a defect which does not necessarily 

 involve total deafness, yet certainly a great impairment of 

 the sense of hearing. 



We naturally do not wonder at the fact that the round 

 window is arranged in the simplest way possible, that is, 

 opening on the middle ear not far from the oval window. 



Let us now attempt to determine what movements would 

 occur in the tube, caused by movements of the stirrup, if 

 this tube were a perfectly plain tube, con- 

 The movement taining nothing whatever but an incom- 

 of the fluid in pressible fluid. It is a decided advantage 



a plain tube to study first a case as simple as can be 



imagined. We are sure that, thus, the 

 elementary foundations of our thought will be clear and not 

 confused by the influence of a complexity of conditions and 

 a sum of powerful prejudices which almost inevitably ac- 



H 



Fig. 3. Movement of fluid in a plain tube 



company a complexity of conditions. Let us try to keep clear 

 of such influences. In figure 3 we see the anatomical facts 

 of our imaginary case diagrammatically represented : a long 

 and narrow tube, two windows at one end, one of these win- 

 dows containing the stirrup, the other end of the tube closed. 



