Evening star., 1900-08-18

ton it is to guide our movements If there
are groups of nerve cells destined for the
purpose of receiving messages from eyes
and ears, the Intelligence department. of
the brain, there are other groups that su-
pervise the work of the heart, and that
control our digestive proceedings, and that
see to it that the duties of the lungs are
duly discharged.
on such principle of division of labor,
We are boun6 to find the varied ways and
works of the nervous system carried out
on different levels, regards the import
ance of the duties performed. Now, 1t hap
pens that the spinal cord. which runs
through the middle of the backbone, within
which 1t Is protected as within bony tube,
Is really a kind of brain deputy in many
respects. 1t acts on the whole as the con-
! hdential servant of the brain, but 1t also
possesses an independence Of its own. Its
duties are of lower nature than those
discharged by the brain. but they are none
the less essential for the perfect ordering
of the body's welfare. Even If the head
office be singularly well organized 1t cam
not exercise Its functions properly in the
absence or inefficiency of the suboffices.
and the special cord is really a series of
suboffices carrying out many actions
which otherwise we might be tempted to
credit to the share of the brain.
If we divide the spinal cord of frog and
irritate the foot the leg Will be moved
after the fashion in which the uninjured an
imal would resent being tickled. Here We
have separated the brain from the feet.
is not lost. That which the brain does in
the frog apparently is not so much to carry
out movements, but to initiate and control
them If frogs legs be allowed to come
in contact with some weakly irritating fluid
the legs naturally will be withdrawn after
an interval. Time after time the action will
go on til We can gauge fairly the period
which will eIapse between the Withdrawals
of the legs and their descents. If, now, the
spinal cord be divided below the brain
we find these movements much accelerated.
They proceed at a quicker rate, because
tn brain control is removed, and the mech
anism of the animal is left, as 1t were to
run wild, like an engine from which the
influence of the flywheel has been removed.
But we may find evidence that the spinal
cord of the frog may control actions in a
fashion that would almost lend belief to the
idea that 1t is much more than a mere brain
deputy. Cut off a frogs head carefully, so
that there may be as little disturbance of
parts as is cNlsistent with the performance
of this operation. We have removed the
brain, of course, and all that is left in the
body of the chief nervous system is the
spinal cord. Now place drop of acetic
acid on the inner side of one thigh of your
headess frog, and you will see the animal
raise the foot of that leg in the endeavor
to wipe the acid off. If, now, you remove
the foot of the same leg and apply the acid
as before the leg will be again raised, but
as the shortened limb falls short of the ir-
ritated spot. the head,ess amphiban will
after an interval raise the other foot and
endeavor to rub away the acid. This is a
well-known experiment, and its teachings
i, are singuarly instructive. They prove to
US that the spinal cord is capable of car
rying out movements of very complicated
| character. movements with a purpose, such
az we should be inclined to believe were
controlled by the brain alone.
Pass now to the case of the man. Here,
| injury and accident. unfortunately, supply
| us with a parallel instance to that of the
| frog If the spinal cord of a man be divided.
say in its middle part the lower half of the
| body Is paralyzed. He is unable to move 1t,
! and he has lost all sensation in that half.
Hut II the feet be tickled the legs will be
! drawn up, although the man is not con-
| scious of making the movements. and is
| unaware he is putting his muscles into ac-
| ton until he sees the motions Of his limbs.
| Here We again come in contact with the
\ idea of the independence of the spinal cord.
! We see that consciousness has nothing
whatever to do with the work of the cord
| any more than when we tickle the foot OF
! a sleeping person and the leg Is moved we
| can assert that he Is conscious Of his ac-
| ton.