Mr. Home's additional Remarks, Sec. 159 



Some additional Remarks, on the Mode of Hearing in Cases where 

 the Membrana Tympani has been destroyed. By Everard 

 Home, Esq. 



After having communicated to this learned Society, the very 

 curious facts contained in Mr. Cooper's paper, which prove that 

 the organ of hearing is capable of receiving all the different im- 

 pressions of sound, when the membrana tympani has been 

 destroyed, it may not be improper to explain, from the obser- 

 vations contained in a former paper on this subject, in what 

 manner this may take place. 



It is there stated, that any vibrations communicated directly 

 to the bones of the skull, are as accurately impressed upon 

 the organ, as through the medium of the membrana tympani. 

 The office of that membrane is therefore to afford an extended 

 surface, capable of receiving impressions from the external air, 

 and of communicating them to the small bones of the ear; 

 which a membrane would be incapable of doing, unless it had a 

 power of varying its tension, to adapt it to different vibrations. 



In the above cases, in which this membrane, the malleus, and 

 the incus, had been destroyed, it would appear that the stapes 

 was acted upon by the air received into the cavity of the tym- 

 panum, and communicated the impressions immediately to the 

 internal organ. This not happening for some months after the 

 membrane was destroyed, probably arose from the inflamma- 

 tion of the tympanum confining the stapes, and rendering its 

 vibrations imperfect. 



