VOL XC.] PHILOSOPHICAL TRANSACTIONS. 575 



low as in the human ear; and the intervals in their scale will be more minute, in 

 consequence of the slightest tremor communicated by the action of the radiated 

 muscle to one end of the slender bone being immediately conducted to the internal 

 organ; while in the human ear it has to pass from one bone to another, before it 

 arrives at the vestibulum. The cochlea has been considered by all physiologists as 

 one of the most intricate and curious parts of the ear, and on that account had a 

 most important office assigned to it. This however is now to be transferred to the 

 membrana tympani; and, on attentive consideration of the subject, it will appear 

 impossible for the cochlea to be of any use in modulating sounds, since the ear is 

 only intended to convey impressions received from external bodies; hence, no im- 

 pression can be communicated to the cochlea, which has not been transmitted by 

 the membrana tympani. But if all the varieties of sound are repeated by the 

 membrana tympani, no modulation in the cochlea is required; and when it is con- 

 sidered that the cochlea contains water, instead of air, the effect on every part will 

 be found to be simultaneous. That the cochlea is neither absolutely necessary to 

 fit the organ to be impressed by sounds communicated through air, nor to render 

 it what is termed a musical ear, is sufficiently proved by that part being wanting it) 

 birds, whose organ is particularly adapted to inarticulate sounds. Some birds, 

 particularly bulflnches, can be taught to sing various airs, though it will be always 

 in high notes. 



If it should be found that birds hear less accurately than quadrupeds, it will 

 favour the idea that the great delicacy of structure of the cochlea, is intended to 

 render the nerves which are spread on it more readily impressed by weak tremors, 

 than those in either the vestibulum or semicircular canals. The cochlea and semi 

 circular canals must be considered as 2 of the most important parts of the ear; 

 their peculiar forms are no doubt adapted to some essential purposes; but what are 

 the precise advantages derived from their particular shape, is at present unknown. 

 There is however much ground to believe, that a more extensive knowledge in 

 comparative anatomy, joined with future observations, may clear up this very 

 curious and obscure part of the physiology of the organ of hearing. In the ele- 

 phant, the small bones, the cochlea and semicircular canals, are larger than those 

 in the human ear, nearly in the same proportion with the increased size of the 

 membrana tympani. In that animal, there is a very remarkable peculiarity; which 

 is, a cellular structure occupying the upper and posterior part of the skull, inclosed 

 between the 2 tables communicating by a considerable aperture with the cavity of 

 the tympanum, and lined by a similar membrane: the cells communicate freely 

 with each other at their lower extremities, but not near the upper, forming irre- 

 gular cylinders, placed in a converging direction, towards the cavity of the tym- 

 panum. There is no middle bony septum, separating the cells of the skull 

 belonging to one ear from those which open into the other, but a ready communi- 

 cation between them. On the anterior part of the skull there is also a similar 

 cellular structure, only much smaller, which communicates with the nose, but is 



