The Indianapolis journal. [volume] (Indianapolis [Ind.]) 1867-1904, 1896-01-26
THE EARS OF ANIMALS
VISIBLE ORGANS OF HEARING ARE
VERY FREQUENTLY LACKING.
Absence of the Outer Ear Not Always
Fish and MOllusks May Hear.
Robert BLIGHT. in New york Post.


We are accustomed to associate hearing
with visible ears. Not very long ago an ar
ticle going the rounds of the journals
treating the external ear as an index OF
temperament. With that this paper has
nothing to do. for its object is not to discuss
human ears, but to give hint or two as to
the different kinds OF ears met with in the
animal kingdom.
1t is well known that, according to the ac-
copied theories Of light and sound, these
phenomena are the results OF fluctuations OF
a universal medium to which wave-motion
can be communicated. Just as when you
drop stone into vessel containing water
wave-motion is set up, and is continued un-
til 1t strikes the margin, so wave-motion is
set up by expended energy in the medium,
and is continued until its course Is stopped
in some way or other. The undulations of
light travel at the rate of $4,000 miles Tin
round numbers) per second, while those of
sound travel over 100 feet Tin round num-
bers again, in the same time. Not only is
there wonderful difference in the rate OF
travelling. but also in the length Of the
waves. The wave-length of the sound pro-
duced by tuning fork is 24.4 inches.
while for the production of white light (sun-
light there will be A, 400 waves in an inch,
for red light $3.50, and for violet $780,
Then again, when the sound of the tuning
fork makes only SIP vibrations in a second,
white light makes 541 millions of millions,
red 45S millions of millions and violet TT
millions OF millions.
1t is reasonable to expect, therefore, that
the organs of man and the other animals
which are prepared to yield impressions of
light and sound will be very different in
construction; and so il is with eyes and
"A
not only so. When the conditions under
which any creature lives demand conscious
ness OF light, or of sound or both, We shall
find that the organs correspond to the pre-
dominance or equality Of the demands.
Most readers are acquainted with, at all
events. the general principles on which the
human ear is constructed-an outer ear; an
external opening and passage; membrane
across that passage called 1.-THE drum" a
hammer" the second "the anvil and the
third the stirrup;" an oval opening in the
partition i OF. of bone between the drum nc AN
tened plate OF the stirrup; and the laby-
rinth. The simple mechanism Of hearing
may be put thus: the vibrations of sound
strike the drum, are communicated by 1t
to the chain of bones. and are passed on
by them to the brain. The labyrinth deals
with differences Of pitch" in sounds and
of motion.
Now, just as we find lowly forms of other
organs among the lower animals" so do
very curious. The lowest animals do not
appear to have any organs which can
| definitely be called ears, although, as in the
| case of earthw0rms, they are very sensitive
| to the vibrations of solid objects. such as
may be caused by some one walking on the
| surface of the eartn. Strangely, however
we find evidences OF organs of hearing
among the jelly-fish, of which you may see
| specimens stranded on the seashore after
| every tide. And, what is very remarkable
| no case where both organs for hearing and
organs for seeing are developed in the same
| species among these medusae. Taking the
| species which have auditory organs; we md
| in some open-mouthed pits provided with
| sensitive hairs; in others the pits contain,
| not chain of small bones. but lump. or
| called ot6liths ear-stones; while in 9TH
| ers, again, the pits are not open, but closed.
thr Tne to ftv earsstones so arranged in
| double line in the cell so as to form a
| crescent. In another species the number Of
| eighty! a sea-cucumber which lives in the
| depths Of the ocean has ffty-six or these
| auditory organs.
THE CRAYFISH EAR.
A crustacean, not unlike shrimp in form,
| has its ears in its tail, If we may so call the
| terminal segment, while another-the cray
| fsh-has them at the base of the feelers on
| the head. In the crayfish the ear is open,
| but bristles prevent foreign matter from
| entering. The cavity is filled with gela-
| tinous fluid in which otoliths float. These
are affected by the vibrations communicated
| by sound in the water: in their turn they
convey the vibration, to certain hairs which
| line the cavity; these forward the message
| to the nerves, and finally it reaches the
nerve center of the creature.
| Insects like grasshoppers, crickets and To-
some on the middle of the body, others on
| the legs. Whatever other uses the Great
| ures may also make of these organs, they
"a
| find a membrane stretched across a cavity
| with opening to the external air, and
at the end of an auditory nerve. 1t would
| be hard, indeed, if the chipping. cicada, 1.-THE
| cricket on the HEARTH, and the querulous
katydid could not be heard by their com
| panions 1t is said that those pests in the
| house-the flies-can hear by means of some
| rows of corpuscles on the knObbed threads
which represent the hind wings of other in.
sects. :. 1t is uncertain whether bees car
| hear. If not, then, all the labor of the old
fashioned bee-keeper In beating tin kettle
at swarming time is in vain. Some natural
| lists who have tried them with every kline
| of sound and noise deny that they can hear
| Others. equally confident. assert that they
| are very sensitive to the calls OF their queer
at least.
Some of the mollusks have very remarka.
BILE organs for hearing. A good instance Is
the garden slug. In its neck you would see
under microscope pair OF globules filled
! with clear fluid. In these are minute ear.
% s SWINE 70 apS then
another, but in no instance striking the
| walls of the cavity. If the globules are
| matured, the motions cease. The imagina
ton will ask whether shellfish, or mol
| lusks, can produce sounds which can bt
| mutually heard. Whatever may be true
of the division as whole, IL is certainly
true that some can emit sounds. Two sea
slugs were found by Prof. Grant to MAKE
sounds which he compared to the clink O
fish have ears which follow the plan Of thu
mollusks organ; and. indeed. as on
watches the uncanny-looking octopus in
corner of rock-cavity, ii Is easy to imag
inc that while looking at you with tina
CLASSY eye he is also listening to what yo'
say.
A careful angler tells you not to tall
while you are fishing. Probably a quie
| conversation will do no harm, but it mus
though sounds from the air may not reacl
| them. One of the oldest arrangements o
all is found in some fishes The air-bladde
sends off fibres which are attached to mem
braneS stretched across cavities in tn
| skull, and from these membranes the vi
| bratons of sound are conveyed to the air
bladder. Such is the case with the perch
WHILE more strange still. in the carp tire
little bones aid the transmission of sound.
TOADS CAN HEAR.
The ears of frogs and toads begin to ap
preach the type with which We are mos
familiar, and very effective ears they ar
too. for pet toad kept for several year
would always come from his hiding plac
when I made low Kissing sound.
Adders may be deaf or hard of hear
ing hut rentiIes are furnished with ears