PHYSIOLOGY OP THE MIDDLE EAR. 193 



brane of the foramen rotundum gives way, "and this leads the course 

 of the undulations of the fluid in the labyrinth in a certain unchange- 

 able direction." The explanation of Sir C. Bell is not as convincing to 

 us as it seems to be to himself. The membrane of the foramen rotun- 

 dum does not appear to be required for the undulation in the cavities 

 of the labyrinth, which he describes ; as the liquor of Cotunnius can 

 readily reflow into the aqueducts of the vestibule and cochlea. The 

 principal use of these canals would seem, indeed, to be, to form diver- 

 ticula for the liquor when it receives the aerial impulses. Sir C. Bell 

 cites the case often quoted from Riolan of an individual who was 

 deaf from birth, and was restored to hearing by accidentally rupturing 

 the mernbrana tympani, and breaking the ossicles with an ear-pick: 

 "disrupit tympanum, fregitque ossicula, et audivit." In these and 

 other cases, in which the membrana tympani and ossicles have been 

 destroyed, and the hearing has persisted, the vibrations must have been 

 conveyed to the parietes of the internal ear through the air in the cavity 

 of the tympanum ; and, notwithstanding the charge of " absolute con- 

 fusion of ideas," brought against such individuals as Scarpa, 1 Magendie, 

 Adelon, and others, who believe that the foramen rotundum receives 

 the undulations of air, we must confess, that the idea of the communi- 

 cation of vibrations through that medium, as well as through the mem- 

 brane of the foramen ovale, and the osseous parietes of the labyrinth, 

 appears to us most solid and satisfactory. 



The ossicles or small bones have given occasion to the wildest specu- 

 lations. At the present day, they are considered to fulfil one of two 

 functions ; to conduct the vibrations from the membrana tympani, 

 or to stretch the membranes to which the extremities of the chain are 

 attached. Both these offices are probably executed by them ; the 

 malleus receiving the vibrations from the membrana tympani, and con- 

 veying them to the incus, the incus to the os orbiculare, the os 

 orbiculare to the stapes, and the stapes to the membrane of the foramen 

 ovale, by which they are transmitted to the liquor of Cotunnius. M. 

 Savart conceives, that the chain of ossicles is to the ear what the bridge 

 is to the violin. It has been already observed, that the ossicles are 

 not essential to hearing, although they may be required to perfect it ; 

 and that they may be destroyed without deafness being produced, 

 provided the membrane of the foramen ovale remains entire, and the 

 parts within the labyrinth retain their integrity k If, in the removal of 

 the stapes by ulceration or otherwise, the membrane of the foramen 

 should be ruptured, the liquor of Cotunnius would of course escape, 

 and partial or total deafness result. In some experiments instituted 

 by M. Flourens on pigeons, he found, that the removal of the malleus 

 and incus did not have much effect upon the hearing ; but when the 

 stapes was taken away it was greatly impaired, and still more so when 

 the membranes of the fenestra ovalis and fenestra rotunda were 

 destroyed. 



The JEustachian tube is an important part of the auditory apparatus, 



* Anat. Disqnis. de Auditu et Olfactu., Ticin, 1789; and De Structure. Fenestrae Rotundse 

 Auris, &c., Mutin., 1772. 

 VOL. I. 13 



