4 UNIVERSITY OF MISSOURI STUDIES 



pump, that is, an alternate condensation and rarefaction of all the 

 particles of air almost simultaneously. This condensation and 

 rarefaction always acts in the same sense (positive 

 or negative) on both windows of the tube. According to 

 the laws of hydrodynamics no motion in the fluid of the tube 

 can result from the difference in size of the two windows. It 

 is hardly comprehensible, therefore, why we find in literature 

 lengthy discussions of the question whether it is the round 

 or the oval window through which "the tone waves" enter 

 the inner ear. They do not enter through either window 

 since they do not occur in the middle ear, the volume of this 

 cavity being too small to contain whole tone waves. Only 

 after complete destruction of the tympanum would the ques- 

 tion as to the manner in which an air wave strikes the two 

 window's attain practical importance. Under normal condi- 

 tions we must regard all the air particles in the middle ear 

 as being, at any time, of identical density, and, thus, as unable 

 to produce any movement in the inner ear. 



If there were no ossicles, the fluid in the tube would 

 remain practically motionless. But to the membrane of the 

 oval window is attached the plate of the 

 Disturbances stirrup which has a somewhat rigid con- 



within the tube nection with the tvmpanum. The result 



are caused by • .« . . r . , . _ 



J is that everv movement ot the tvmpanum 



motion of . • 



the stirniD ls accom P anie d by a movement of the 



stirrup in the same (positive or negative) 

 direction. Whenever the tympanum moves inwards, the air 

 in the middle ear is, of course, somewhat condensed. But 

 this condensation or rarefaction has no relevant influence on 

 the fluid in the tube, as before mentioned. The alternate 

 condensation and rarefaction of the air in the middle ear, re- 

 sulting from like processes in the external auditory passage, 

 is an unavoidable, but functionally negligible by-product of 

 the mechanical process in question, bearing no direct rela- 



