ANIMAL MECHANISM. 307 



d, e, y, the vestibulura. 



g, to q, the semicircular canals. 



g t h, i, the posterior ; k, I, m, the superior; o, p, q, the exte- 

 rior canal. 



1, 2, 3 the lamina spiralis, seen on itg under surface; 3, the two 

 sacs so often mentioned in this .tract, in the vestibule, which, 

 viewed in this plan, look like one. 



t, u, the membranous posterior canal. 



v, w, x, the superior membranous canal, uniting with the last, at 

 x, y, z, the exterior membranous canal. 

 Tliis diagram exhibits the distribution of the acoustic nerve in 



the labyrinth ; the large branch goes to the cochlea, and the three 



others, smaller, to the vestibule, and three semicircular canals. 



PERMANENT DEAFNESS. 



A total deafness implies a destruction of the organ : 

 but I apprehend there are only a very few persons in this? 

 condition. Even in those unfortunate fellow-beings who 

 are deaf and dumb, the faculty of hearing, to a certain 

 extent, still exists. They hear the report of a cannon, 

 or heavy thunder, which act so powerfully on the body as 

 to rouse the sleeping energies of the acoustic nerve. In 

 fact, the tremor is communicated by being propagated 

 through the bones of the head. Fishes, of the bony 

 kind, have the organ of hearing acted upon in the same 

 manner, as the nerve is completely cased up in solid 

 bone, without either drum-head or external openings. 

 Many years ago, in the course of a visit at the Hartford 

 deaf and dumb Asylum, I ascertained many of the 

 pupils could feel sounds, which they could not hear, by 

 holding a twine between the teeth, while the other end 

 was tied to a musical instrument at considerable dis- 

 tance. One young gentlemen assured me that he derived 

 a pleasurable sensation from the vibrations of the strings 

 of a piano. It is my firm belief that many persons who 



ting the nails, &c though in that .climate <he secretions may be 

 fluid, in greater abundance, and discharge freely, th.e plucking of the 

 hairs and frequent introduction of scraping instruments render the 

 organ irritable, and less accurate in the perception of sounds. 



Tumors, ulcerations and other troublesome complaints are 

 brought on by picking them. A sudden pressure on the corda tym- 

 pani, a nerve belonging to the face, which crosses the drum-head, 

 by the head of a pin, may forever after render it liable to inflame 

 on the slightest exposure. 



Fluids ought not to be poured into the external ear to drown in- 

 sects, aa the worst consequences may ensue. 



