The Lambertville record. [volume] (Lambertville, N.J.) 1872-1968, 1879-07-16

lVoatquoiy ~ II retFstobeu, or Uent towards the
peipendicular, raised from the point Of inn
pact, because it passes into denser medium.
It is thereby rendered more conyergent or ap-
proaches the axis of the cone. In passing
through the aqueous humor little variation
is produced as it is of about the same density
as the cornea. This conveyance causes a
greater number of rays to be collected to-
wards and enter the pupil, and of course to
pass through the crystalline lens, which be-
Ing of increased density, the consequence is
stiff the more increased from the increased re-
fractive power Of the medium end the convex
ity of the lens, after the ray has passed the
crystalline lens, it energies into a rarer medic
um (the vitreous humor) and is therefore re-
ffacted from the perpendicular but the
shape of the posterior surface of the lens is
such that the convergence is further increas-
ed, and meets the other rays at the focus on
the retina land there presenting a picture or
representation Of the object on the retina in
an inverted position, The quality of light
passing into the eye, at any one time, is reg
ulated by the iris. This is a very important
part of the apparatus of vision. BY the con-
traction and dilation of the iris the pupil is
made large or small, according to The intens-
ity of. light In the glare of a bright sun this
onening that let's in the light becomes very
small bal insthe dark tits very wide open,
because the eye then needs all the light it can
get. The eyelashes serve to keep light bod
les, flying in the air, from entering the eye,
by the aid of the muscles of the eyelids which
act so quickly in closing them, thus shutting
out all intruders. The, eyebrows, besides be-
ing an ornament, are of some use as protec-
tion.s If they were not there, the perspira-
tion on the forehead would continually run
down into the eyes, and would irritate and in
flame them. There is also beautiful appa-
ratus for moistening and washing the eye.
The tear-gland that makes the wash for the
eye is situated above and a little towards the
outer side oornersof the eye. The tears are
conveyed from this little factory by ducts,
yeryismall in size, which pour It over the sur
face of the eye. They serve to keep the eye
moist so that 1t can move about in its socket
easily by the muscles. They also serve to
wash out the substances that get into the eye
For the purpose of moistening the eye, the
tears come from the gland in small amount
all the time. OF course, there must be some
means for passing off the tears, or they would
continually run over the edges of the lids. If
you will look at the edges of the eyelids, you
will see on each, near the corner OF the eye
toward the nose, a very small opening. Into
these openings the tears go, and pass through
two ducts which unite in one, called the lach-
rymal duct, which terminates in the nose.--
Such is the wonderful apparatus of the hu-
man eye at the construction of which we
may well admire the skill and power of the
All-wise Creator.
We will now turn our attention to the Or
gan of hearing, or addition. By this appa-
ratus the mind acquires the knowledge of
sounds. 1t is, indeed, very complicated, and
some part of it very delicate. It is divided
into three parts the external ear, the middle
ear or tympanum, and the internal ear or
labyrinth. The external ear is constructed of
a cartilaginous or gristly framework, covered
with integumeut or skin, loosely attached to
the bones of the head, and performs the Office
of collecting and receiving the vibrations of
sound coming from various quarters. After
having been received by this part of the ap-
paratus the vibrations or waves of sound are
transmitted to the middle ear, or drum,
through the auditory canal, technically called
meatus auditorius externus. Il Is about an
inch and quarter in length, and lined by q
continuation of the external skin. The skin,
or integument, towards its outer portion is
beset with small hairs, and secretes from
glands underneath, a waxy substance, very
bitter to the taste. By these means the pass.
age is protected from the Transmission of par
ticles or insects. AS the sound passed through
this canal, it strikes against a membrane
stretched across the cavity, called the men,
brana tympani. This is the drum of the ear.
Immediately behind this membrane Is the
cavity of the middleear or tympanum. This
cavity COMMUNICATES with the pharynx by
narrow passage called the Eustachian tube
Thus, If you shut your mouth and close the
nostrils with your fingers, and then force the
air strongly from your chest into the mouth,
you can feel the air pass through this tube in
to the ear. The cavity Of the tympanum, or
middle ear, is nearly half inch in length,
and Is trayersed by chain of small bones,-
three In number, namely as follows maleus,
being the shape, of a hammer incus, the
shape of an anvil and stapes that of STIR
rup. These bones serve to convey the sound
across this cavity to membrane on the oppo-
site side striking against this, IL is thence
communicated to the labyrinth or internal
| Il.