SCIENTIFIC TRACTS. 



NUMBER XII. 



ANIMAL MECHANISM. 



THE EAR. 

 BY JEROME V. C. SMITH, M. D. 



THE ear, that organ by which we are made sensible 

 of the imptession of sound, in the higher species of ani- 

 mals, is a very complicated instrument. ^ It is a beautiful 

 piece of mechanism, more intricate than a timepiece, 

 ' and no less wonderful in structure, than the arrangement 

 of the numerous pipes of a church organ. 



It is a curious circumstance in the economy of organ- 

 ized beings, that the central portion of the human ear, 

 termed the saculus vestibnK, hereafter to be described, is 

 the basis of the apparatus of hearing in all animals with 

 which naturalists are acquainted, with the exception 

 of insects,*, but becoming more and more complex as 

 inferior grades approximate the physical perfectibility of 

 man. 



Sound being a vibratory motion of the air, first put in 

 motion by a solid body, is collected by the ear as the 

 pulsations travel onward, and transmitted directly to the 

 auditory or seventh pair of nerves, mere filaments, like 

 two white cotton threads, which communicate the fact of 

 these vibrations to the sensorium, or, in other words, 

 produce a corresponding Change in the brain. 



fc The antenna of insects are considered the only organs with 

 which they are furnished, that convey a sensation analogous to 

 hearing. By the vibrations communicated to the body, through 

 these, they are probably made susceptible of simple sonorous im- 

 pressions. 



VOL. I. NO. XII. 25 



