18 Mr. Home's Lecture 



muscle to one end of the slender bone being immediately con- 

 ducted to the internal organ ; while in the human ear it has to 

 pass from one bone to another, before it arrives at the vestibu- 

 lum. 



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, how- 

 ever, is now to be transferred to the membrana tympani ; and, 

 upon attentive consideration of the subject, it will appear im- 

 possible 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 impression can be communi- 

 cated to the cochlea, which has not been transmitted by the 

 membrana tympani. But, if all the varieties of sound are re- 

 peated by the membrana tympani, no modulation in the cochlea 

 is required ; and, when it is considered that the cochlea contains 

 water, instead of air, the effect upon 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 in birds, whose organ is par- 

 ticularly adapted to inarticulate sounds. Some birds, particularly 

 bulfinches, can be taught to sing various airs, although 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 upon it more readily impressed by weak tremors, 

 than those in either the vestibulum or semicircular canals. 



