690 THE SENSE OF HEARING. 



make it rest obliquely in tlie fenestra ovalis, depressing 

 that side of it on which it acts, and elevating the other 

 side to the same extent. 



When the fenestra ovalis and fenestra rotunda exist 

 together with a tympanum, the sound is transmitted to the 

 fluid of the internal ear in two ways, namely, by solid 

 bodies and by membrane ; by both of which conducting 

 media sonorous vibrations are communicated to water with 

 considerable intensity. The sound being conducted to the 

 labyrinth by two paths, will, of course, produce so much 

 the stronger impression ; for undulations will be thus 

 excited in the fluid of the labyrinth from two different 

 though contiguous points ; and by the crossing of these 

 undulations stationary waves of increased intensity will 

 be produced in the fluid. Miiller's experiments show that 

 the same vibrations of the air act upon the fluid of the 

 labyrinth with much greater intensity through the medium 

 of the chain of auditory bones and the fenestra ovalis 

 than through the medium of the air of the tympanum 

 and the membrane closing the fenestra rotunda : but the 

 cases of disease in which the ossicula have been lost with- 

 out loss of hearing, prove that sound may also be well 

 conducted through the air of the tympanum and the mem- 

 brane of the fenestra rotunda. 



Functions of the Labyrinth. 



The fluid of tlw lalyrinth is the most general and constant 

 of the acoustic provisions of the labyrinth. In all forms 

 of organs of hearing, the sonorous vibrations affect 

 the auditory nerve through the medium of liquid the 

 most convenient medium, on many accounts, for such a 

 purpose. 



The function usually ascribed to the semicircular canals is 

 the collecting in their fluid contents, the sonorous undula- 

 tions from the bones of the cranium. They have probably, 



