anatomy. 
labyrinth. The final use of the muscles 
which moves these bones is unknown. 
The labyrinth of the ear consists of three 
parts : — 1 . A spiral bony canal, twisted like 
a snail-shell, and thence called the cochlea. 
2. Three semicircular bony canals : and ■:>. 
A small cavity, called the vestibulum, into 
which the cochlea and the semicircular 
canals open. These parts are formed of the 
hardest bone in the body, almost equal in 
solidity to ivory, and the petrous portion of 
the temporal bone, which incloses them, is 
of a similar structure. In the fetus the 
labyrinth is surrounded by a softer and 
looser kind of bone, so that it can be most 
easily dissected at that age. 
The vestibulum is about equal in size to a 
large pea, and the feneatra evalis opens into 
the middle of the eavity. It has also five 
openings from the semicircular canals ; the 
superior and exterior joining by one. of their 
extremities, and opening by a common 
hole. 
The cochlea has two turns and a half. Its 
canal turns round a bony centre, called the 
modiolus, to which is attached a thin plate 
of bone, projecting into the cavity of the 
cochlea, and named lamina spiralis. 
This projecting plate divides the canal of 
the cochlea into two parts; one opening 
into the vestibulum, the other at the fenes- 
tra rotunda. The latter is called the. scaia 
tympani, the former scada vestibuli. 
* The vestibulum, cochlea, and semicircu- 
lar canals are lined by a delicate vascular 
membrane, on which the portio mollis of the 
seventh pair of nerves is distributed. This 
membrane contains a clear water. 
The filaments of the auditory nerve pass 
from the meatus auditorius interims through 
a number of very small apertures, which 
lead to the labyrinth, and they terminate on 
the vascular membrane of the labyrinth, so 
that the nervous pnlp is exposed almost 
bare to the contained fluid. The distribu- 
tion of the nerve on the cochlea is particu- 
larly beautiful. The aqueducts of the ear 
are two very fine tubes passing from the vesti- 
bulum and cochlea to open on the surface 
of tire dura mater. 
ORGAN OF SMELLING. 
The nose is a cavity of very irregular 
figure, formed chiefly by the bones of the 
face, and communicating with the various 
sinuses or bony cells formed in the head. 
It is separated from the brain above by 
the cribriform lamella of the ethmoid bone. 
This separation a perfect one, and the 
two cavities of the cranium and nose are 
wholly distinct from each other, although 
they are supposed by the uninformed in 
anatomy to communicate together. 
The bottom of the cavity is formed by 
the upper surface of the palate. 
The general cavity is divided into two 
equal halves, called nostrils, by the septum 
nariuro, a thin and flat bony partition des- 
cending from the cribriform lamella to the 
palate. The flat surface of the septum may 
therefore be said to form the inner side of 
the nostril; and its outer side presents three 
bony eminences, called the concha; narimn, 
or turbinated bones. 
Moreover, the following excavations or 
sinuses open into the cavity at various parts. 
Two frontal sinuses ; numerous cells of the 
ethmoid bone ; two sphenoidal sinuses ; and 
two gr eat hollow s in the upper jaw bone, 
called the antra, or maxillary sinuses. 
The front openings of the nostrils are well 
known. This aperture is heart-shaped in 
the skeleton, the broadest palt being to- 
wards the mouth ; but it is much altered in 
the recent subject by the apposition of 
pieces of cartilage, the broadest of which 
are the lateral portions termed alee nasi. 
Behind, the nostrils open by large apertures 
into the upper and anterior part of the 
pharynx, above the velum pendulum pa- 
lati. 
The sides of the bony cavity just described 
are covered by a thick, soft, and very vascu- 
lar membrane, called membrana sclmeide- 
riana, or pituitaria. Its surface is constantly 
moistened by a secretion of mucus from the 
arteries, with which it is very copiously 
supplied. This prevents the effects which 
the current of air in respiration would other- 
wise produce, of drying the membrane. It 
is only an increased quantity of this se- 
cretion, altered too somewhat in its qua- 
lity, that is discharged from the nose in 
colds, and which is popularly supposed 
to come from the brain. This membrane 
extends into the cells which communicate 
with the nose, but is thinner and less vascular 
there. 
The ethmoidal cells open into the cavity 
of the nose, partly above, and partly under 
the loose edge of the superior turbinated 
bone. The frontal sinuses open into the 
front of these cells ; and the sphenoidal 
sinuses into the back part of them. The 
antrum maxillare has a round opening be- 
tween the two turbinated bones. The nasal 
duct opens under the inferior of these bones : 
and the expanded orifice of the eustachian 
