ANIMAL MECHANISM. 

 THE AUDITORY NERVE. 



There is no part of the intricate organ we have been 

 explaining, more absolutely difficult to display and to fully 

 understand, in all its relations, than the nerve of hearing, 

 and we shall therefore avoid all laborious anatomical des- 

 criptions, and merely generalize. All the nerves origina- 

 ting in the brain, are reckoned from before, backward, 

 that is, beginning with olfactories, at the nose, and 

 ending with the tongue, or lingtials. 



In this order, the auditory is the seventh, a pair 

 precisely alike on the two sides of the brain; not much 

 larger than cotton sewing threads ; it enters the cochlea 

 first through a sieve like orifice, on one side of a bone 

 that projects from the inside of the skull towards the 

 brain. This depression where the nerve enters, to travel 

 outward, towards the external ear, is the meatus audito- 

 rius interims. It assumes a variety of shapes in distribu- 

 ting itself in the various tubes, sacs, canals and pits we 

 have been exhibiting. At some points, many delicate 

 threads are discoverable, side by side : at others, fibres 

 are seen floating in the surrounding fluid, from the main 

 trunk : at others, the nerves assumes the form of a flocu- 

 lent paste, and at others, a woolly texture. The whole, 

 distributed thus elaborately, constitutes the nerve of 

 hearing. The sense of hearing is not confined, in a 

 healthful condition of the organ, to any one particular 

 part or point : the sensation is perceived in the whole at 

 the same instant of time. The question now may arise, 

 why was it necessary to construct such an intricate 

 machine, if one part of it has not a higher office to sus- 

 tain than another ? 



Economy was the object : to pack as much as possi- 

 ble in the smallest space, is observable in all animal 

 mechanism. No other kind of arrangement of cells in 

 the small block of bone in which these are found, would 

 or could have afforded so much surface to spread out 

 such an extent of nerve. This then is the probable rea- 

 son for semi-circular canals, the cochlea and their ap- 

 pendages. 



