Star.
London, England, 1828-12-08 00:00:00

HYSIOLOGY OF THE EAR.

ith great pleasure, the following extract frogs Mr.
we on the Physiology and Zoology of the Ear in
nab, delivered at the Royal Institution of Great

cavity seems to be the general stricture of
F hearing, as best fitted for receiving and
nod; in the cliff:rent cla,ses of animals it
onsiderable varieties iatbeappearaoce and
is formation, and its appendages: in man,
more perfect io structure than in any other
it is also of more importance to hint than
animated creature. To enable us to fores
on this important subject, I shall now snake
ul observations on the varied structure sI
tr different animals.
all, at far as we know, possess thiamin; it
y doubted with respect to &his, bat the late
nd discoveries in cooper atiire anatomy have
istablished their possession of this sense. In
imperative anatomy on this subject, Haller,
F Physiology, justlyobserver, that the situa-
, and sine of parts most be learned frogs
uses and motions must be drawn from ani.
vier (I), we find,, Las divided the animal
to four divisions, being a regular gradation
icated to simple, through the whole series,.
rith man, and terminating iiith insects found
fluid. The first ,division consists of' the
which extends from man to the eel o ter-
econd is the molt:sea, which compriseafrons
sh tothir barnacle or oystere The third is
ta, extending from the crab or lobster to
onto or leech. Theism is the radiate, corn-
a the star fish, or medusa, to• an animacule
i. The external and• tympanum do not ea-
d the vertebralia ; nor do they exist in all the
!longing tothis division. The impressions
organ- of. bearing setrives are conveyed
e medium of air ; that medium acquires,
scion of the.budy communicating.sound, a
notion or vibration ; and asthese :notions or
acceed each other, sound is impressed or
the thin membrani a/etched• obliquely
auditory paisege, as I bite already observed,
roduces a Similar motion, and excites the
easing with a mysterious yet most efficient
a certainty of result invariably correspond-
:onsectnive cais,es of noise. In all animals
livided into an external and internal part,
Terence in the structure of the organ of hear.
ter in the internal ear than in the external.
>eds also, I may observe, the chlfereace is
ter than in the other cles,es of animals ; but
lifferences or varieties of structure ate met
ye may lay &mu as a general rule, that the
ctn. calculated by it for its particular cis-
I and mode of life. On the whole, the sense
may he considered as one of the most power-
if defence that animals possess, by. its indi-
approach of danger ; likewise as the means of
n if individual families, or the congregating
,mber of a species for defence or migration ;
guide of mo.t animals to their prey; hence
en that few animal. are Without. he ear
feet in C.e ted.blooded animals, and it gra.
hes in propulsion to the seeming impnr-
: scale cf. animation;, thus membranes ans.
is ear Are found in wane of the white blooded
d several others which are sensible ot sound,
organ in them has hitherto been but im.
set-named. In examining the external eat
chi, it is fl mid coninwitity to resemble the
lion of a cone, fi on, n at the apex to the best
lithe' anitn•lt, exposed to ilanget,,andliabl.
.kid by man and by beans of piey, has.
aid they are particularly directed back
the coturaty, have their ears directed for.
Say be ved in the lion, the tiger, the ear,
;c their eyes at the same time, tuU and Flo-

- •
they may close it when they become immersed in thel
water; of this st ucture, the Water Shrew is a Striking
example (2). la the manse manner, in the different ,
genera of animals, the exr ernal opening, or meatusoraries
considerably with respect to its length, breadth, and
erection. In the dock-billed animals, it is not only very
long, but singularly tortuous. In all the perfect animals,
or mammalia, it may be almost unnecessary to state
that they unitormly possess a niembrana tympani, a
tympanum with its Eustachian tube opening from that
cavity to the throat; but in the Cetace4 there is an ex
ception, Inv, instead of the throat, it opens in the blow.
ing valve (3). The nsembrana tympani is oo its oder
surface somewhat concave, being slightly depressed in
the middle; all the aninials of this clasg, I may here ob-
serve, pos.ess the two finest:se, the torahs filled by the
bone of the stapes, and the. rotunda, at which com.
meccas the scala tympani of the cochlea. In the Horse
and Ass, again, different from Man, the Eustachian
tube does not directly open into the larynx, but into a
sac, situated in the lateral parts of the lower jaw, and
this formation is peculiar to that class only. In most
of the four-footed mernmalia, there is connected with
the tympanum another cavity, which, from its skim.
don And appearance, may be compared to the Mas-
toid cells in the temporal bone of man; nay, in several
animals, this organ would appear to be a mere bony
cavity* as in the dog, martin, squirrel, hare, sod some
bisulca. In Circopitheca, there is only a partial de,
welopment of this structure to be discovered; while, en
Was ether hand, in horned cattle, and in the pi & the
cavity we have described is parted off into cells, by ntor
merous plates of bone, resembling in some degree the
divisions in a ripe poppy head. In the warm blooded
quadrupeds these see three essicula anditus, the same
as in man, and neatly of the same form; the labyrinth
is a part of the ear which, as far as has been examined
in the four touted mammalia, exactly corresponds with
that of the human subject, but, the cochlea exclusively
belonging to this class has often a turn more than in
man, with some differences of less importance (4)...
To the mainmalia exclusively belongs the external car+
tilaginous ear, which is wanted in the whole class of
birds; but this seeming detect icemply compensated,
especially in those of the rapacious kind, by the. ptecu•
liar arrangement of the feathers round the opening of
the meatus; and in addition to this, several of the last
class; particularly' die ran of owls, 'possess a kind of
valve, situate at the orifice, and consisting its part of a
membranous, and in part of a muscular texture. In its
form, the membrane tympani of birds en its outer nu-
face is convex,. and the tympani of the two ears ate so
connected together by the air cells of the craniumpthat
they have but one ouicula ;indium by which the mem.
brana tympani is connected with the feneura nvalis,
and thus supplies the place of the mallets!, and napes
of the mammalia, when the part corresponding m' the
mallets' is usually of a cartilaginous structure, without
any tensor tympani (5) The Eustachian tubes also
have one common opening on the arch of the palate,
while the labyrinth is conspicuous by large canals pro,
jecting fiom the cranium. There is likewise here se
want of the cochlea, and instead of it, birds possess a
short, obtuse, and hollow process of bone, directed ob-
liquely backwards from the vestibulum; and, like the
cochlea of the mammalia, parted off into two scale,
which one terminates at the fenestra rotunda, where it
receives a portion of the auditory nerve, in the same
manner as the cochlea does in other anim
Besides the remarksalready made on thitikustachian
tube of the cetacea, certain peculiarities in other pasts
of the organ distinguish this class, and from their de-
viating so widely from warns-blooded animals, they
deserve particular attention ; their want of an external
ear is well known ; the opening of the meatus is un-
commonly small; in the dolphin and porpoise the bony
parcis but weakly attached to the skull, and in the
common whalesit is entirely separate. The tympanum
and belle ossea consist of a hard bony substance, for-
merly, but erroneously, called lapis manati, or tibernis;
in the same class the ossicula auditus and the labyrinth,
especially the bony canals, are remarkably small, one
tenon why they were long overlooked. The structure
of-the organ of bearing in the amphibia diiplays Much
greater variety than in the two former classes, but there
is still greeter-variety in the last class. Turtles, frogs,
and most or the' species of the' lizard' kind, possess,
besides the semicircular canals, a tympanum and
Bustachiao tube, like the warm-blooded animals.—
lb the turtle, the membrane symposia resembles
a cartilaginous- mass, covered externallyby the com-
mon skin, or teguments ; their single chieulum it
also very like that of birds. In flogs; a large mem-
prana tympani is conspicuous; their Euttacitian tube,
which is yfnt,sunsists of avidecpeoing at the'fauces
they hive also two cartilaginous ossicula; and a rudl:
rent of vestibulum appear., composed of those soh!
st -ny substances which' assume a more conspicuous
m ii lizards and serpents 16), and in' the three Ibl•
lowing orders; a sort 4 (external meatus appears only
n the solitary inssance of the crocodile amongst all Mei
amphibia. This animal, in common with the lizard,
rzi.ibits also the ossicula, and the ,tong concretions 101 l
he vestibulum already noticed. Beinies the want of i
ympanurts. the foramen ovale in the salamaridei (7) is
I wed bye portion of mrtilage, and sts messibulom
..;onaiess, s)f: a soft-hum In serpeists thee is neithm
YMPOssonzeor EUSUCIIIan tube; with very few clop-
cons, as the blind worm (eerie fregilio), but they
'are a kind of rudiment of asp ossiculuen. In some

=I