New-York tribune., 1873-03-24

ing portion on the aide OF tho head aud the external
auditory canal This canal ends bndly. being entlrey
closed by the membrane of the drum. or the exterha
drumhead. This drum-head. also called tympanic mem
brane or membrane of the tYmpanum forms the part
tion wall between tho external and the middle ear
The middle ear ia called the tympanum, the Latin
word for drum 1t includes the socalled drum cavity
with it's contents; and you will most readily unuers'nu
its construction by keeping my reference 10 '"
drum before your mind. Opposite 10 tne ou'o, uiu'i
head there is the inner drum head caiieu oVa' moi
brane TO distinguish it from another smaller meinDauo
a little below IL. called the round memorane'
IA strc.cbod across round orihce in the bony wall 'ne
round window of the inner Like every oihei w ~
that OF our ear contains air, and has, ai'o'
Or rather long, narrow tube running 10 'hV f'9. fa
mart of the nose and throat, the Eustachlah tuoe
af,er Eustochius the physician who d!scoverou anu "
,,,,S, :, ,, ,,hiob communication is established be-
- ,,o dir NJ the middle and the ar OF the at'oo'
,oro entering the nose and mouth The other ""iS VI
tho drum arc bony; and across the cavity '"eio
chain of three little bones the hammer anvil a"u sun
n resnectlyeiy 80 called from their shape Vho nam
nor beinc imbedded in the outer, and the strrup
,,l,ntod AGAINST tho inner druln'head- LooA I"
this model Imagine on one side the external ear
and mcatus closed by the tympanio memOranei on the
other SIDE of this membrane you have the oones oI tue
ear forming solid bridge between 1t ana the oval me'
brane. You see tnat when move the membrane repre-
sentng the outer drumhead inward the motion Is trans
mitted to the oval membrane.
The internal ear is the most complicated part Of the
hearing organ. have here many casts and models and
drawings assist you in understandingit II closed
cavity containing watery liquid space of suoh ntroacy
that it has received the name labyrinth II is situated
in the hardest portion of all the bones in the body the
stony portion of the temple bone and 1t s here where the
terminal expansions OF the OF hearing are To find
your way in the labyrinth would ask You to look npon
space made up OF three portions the middle and
widest part the vestbule; side, this leads INTO
three narrow arched passages called the semicrcular
canals the other side into long passage, wlch
winds spiray around central axis like an ordinary
snail's SHE'LL and ia called cOcbea the Latin name FOR
snai's she'll In the water of the yesbule and semcir'
cuar canals swins the menbranous labyrinth, closed
bag of delicate elastic tissue also containing water and
having the same shape exactly the bony portion OF the
labyrinth in which it swims. but which it no where
touches. In this membranous labyrinth branch Of
the auditory nerve is spread out. The oochlea Is
really made up OF two winding passages or
staircases one above the other, separated by
sepum without any communication except at the very
top the passage which starts at the vestbue IL Inc
upper one and Is called the vestibular staircase cdd
ueSbui the lower leads toward the tympanic cavity
from which il is separated only by the round membrane
and is called the tympanic staircase tScGd iDmpuhtl
The septum separating them Is partly Dony ana partly
membranOus the bOny portion starts from the cenfal
axis the cOchea but does not reach across 10 the
outer wa TO ts edge is attached the menurinous por
ton which completes the scptu, but instead O Delng
between its layers and is hence called the cochear duct
Here is found the most wonderful structure that mas as
yet been described in the human body.
oTOLTTHs AND FIBERs OF MEMBRANA BAslLARIs.