The Saint Paul globe. (St. Paul, Minn.) 1896-1905, 1899-06-18

spirit-level, which the brain uses to in
form itself of the position of the body.
So long as they are in healthy working
order their reports are trustworthy; but
when any undue force has shocked them,
or any agency, such as sickness, has in
terfered with their workings, their mes
sages are incoherent. and the brain, like
the engineer of a battleship in action
when the men above are blinded and be-
wildered, has nothing to do but let things
go. The expression mind your eyer
then might be changed to mind your
carp with pertinence. If man keeps
the whole mechanism of his ear in order
he should have level head; he should
not be seasick.
DR.. w. H. Howell, of John Hopkins
university says: 1.-THE internal ear is
the site of the true organ of hearing.
The membranous labyrinth (the part Of
the ear beyond the drum Is a complicat-
p ed system of mcmbranous tubes and
sacs in which the f1laments of the audi
tory nerve terminate at particular points.
1t is contained within the bony labyrinth,
a chamber followed out in the hard,
ivory-like, or, as scientists call it, the
petrous (stony) bone. The cavity Of this
bCny labyrinth consists of a bony part.
the Vestibule, and two extremities, one of
which holds the semi-circular canals and
the other the cochlea, a canal shaped
Ikea snails shell. The vestibule is about
one-fifth of an inch in diameter and has
an oval opening in its outer wall. The
selni-circular canals are thin, round
tubes, in diameter one-third to one-ffth
of the diameter of the passages in the
bony framework that contains them. They
arc Semi-tranSparent. Psychologists call
them % the anterior or superior canal;
(2) the posterior canal; 90 the external or
horizontal canal. Their planes are at
right angles to each other, SO that they
occupy the three dimensions Of space. The
external canal is nearly in a horizontal
plane and the other two approach the
vertical That is, enc might be said to
extend east and west, another north and
south and another up and down.
Each canal is dilated at one extremity
into a globular cavity, which Is more
than twice the diameter CT the canal It
self and which is known as the ampulla.
The anterior and posterior canals unite
near the ends that have not these flask
shaped bulbs and enter the vestibule as a
common tube. The outer rims of the ca
nails are attached to the bony walls of
their respective passages, but, except Tor
this slight attachment, the canals float
freely in a fluid called perilymph. Inside
the canals there is a watery fluid called
endolymph, which moves in the tubes, as
does the fluid in a spirit level. The hairs
IN the hair cells within the ampullae float
in this fluid and telegraph to the brain
through the nerves the direction in which
the fluid presses. By these reports the
brain knows which way the head is NOV
ing, whether forward or back, to one side
or the other, or up or down.
In speaking of the work of the semi
circular canals with regard to equili-
brium, DR.. Howell says: THE term equili-
brium, as applied to the condition of the
body, whether at rest or in motion, In
dictates that all the muscles pertaining
to the skeleton are under control Of nerve
centers, so that they combine when re-
quired to resist theeffect of gravity or
10 execute some co-ordinated motion. The
preservation of equilibrium is manifestly
of fundamental Importance in animal life,
and we find accordingly several mechan-
isms sharing in this function. That the
motor co-ordinating centers may act
properly, they must receive sensory i'm
pressions conveying information of the
relative position Of the body at any given
moment. The sum total of these sensa-
lions may be characterized as the sense
Of equilibrium, and 1t is probably not go
ing too far to say that every known
sensation contributes to this fund of in
formation.
THUS in ordinary life the position OF
objects is commonly determined by the
sense Of sight. When one tries to walk
while looking through prism, objects are
not properly localized by vision, and i'm
proper coordination results The contact
Of the soles of the feet with the ground
and that of the surface of the body with
various objects, are common sources of
information as to our relation with the
environments Standing upright, and still