The Eye in its Relation to Health
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By Chalmer Prentice, M.D.
Chicago, A.C. McClurg & Company, 1895
Transcription (c) A. Wik, 2004

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        | Chapter II |  pages 17-23
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NO part of the living body is constructed in
vain.  Every minute portion has some par-
ticular office to perform.  However simple or how-
ever complex any one of these parts may be, it is
so constructed as to facilitate the work that it has
to do.  Each distinct part may be looked upon as a
little engine which is put in motion by the appli-
cation of the motive-force that enables it to per-
form its function.  This motive-force is conveyed
from the place where it is generated, through
conductors called nerves, to the part where the
function is performed; and, like the running of an
ordinary engine, the character of the function is
determined by the character of the motive-force
supply.  If the proper amount of steam is admit-
ted to perform the function of the engine, the
work is properly and evenly done.  If too much
steam is turned on, the engine runs too rapidly
and is likely to do itself injury by over-work.  If
too little is applied, the running of the engine is
very feeble and can be stopped by the slightest
interference.  If the steam is cut off entirely, the
engine stops.  Here we have a perfect analogy
to all functions in the human or animal body.  If
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the motive-force is just adequate to the necessi-
ties of the part, the function will be normal; but,
if the motive-force is in excess, the function will
be erratic and unnatural, exhibiting disturbances
which will be classified as some disease of the
part, which will be of an active nature.  If the
motive-force is lacking in quantity and regularity,
the result will be that the function will be very
feebly performed, and some sluggish, indolent
condition will follow, which will be classified as
an inactive, indolent disease.  These changes,
which are similar in all parts, can be easily noted
and demonstrated in the action of the heart.  In
a state of perfect health, the nerve-centers are
furnishing and sending to this little engine,
impulses of motive-force which give rise to a reg-
ular, unvarying beat of about seventy impulses to
the minute.  Now, if the nerve-centers be excited
in any way, the heart's action at once will mani-
fest the change.  A cry of fire, a terrific explosion,
or the sudden consciousness of some important
news of good or bad import, causes an excitement
of the nerve-centers in which the supply of nerve-
force is temporarily increased, and a larger amount
than usual traverses the various nerves throughout
the entire system.  The heart's action becomes
violent and rapid, manifesting the exact amount
of change of motive-supply from the nerve-centers
to the heart.  We note the changes of action par-

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ticularly in the heart, whereas the fact is, every
function in the whole body is equally affected,
but the change is not so manifest to our ob-
servation; nevertheless, the alteration of function
everywhere in the body is equivalent to the
change in the motive-force supply.  The nature
of the function, whether it be normal or erratic,
is a manifestation of the character of the motive-
force supply, really giving us a perfect idea of the
condition of the nerve-centers from which the
force is proceeding.  This would naturally lead us
to the conclusion that ALL ALTERATIONS OF FUNC-
TION ARE PRIMARILY CENTRAL IN THE NERVOUS
SYSTEM.
  Every organ in the body has special organic
work to perform.  Likewise, the various tissues
of which the organ is constructed have functions
to perform.  Every little living cell, be it bone,
nerve, muscle or any tissue, has a function to per-
form called assimilation.  A cell of adipose or
fat possesses the power to attract to itself carbon,
hydrogen, and oxygen, or matter of its own kind,
in just the proportions of which the cell is com-
posed, and in quantity just sufficient to maintain
the proper size of the cell: surrounding the cell
is the cell wall structure, which is doing a separate
work by drawing to itself matter of its own kind,
but in different proportions to the cell within:
again, adjacent to this is a cell of muscle, bone,

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periosteum or other structure, each attracting dif-
ferently unto itself elements of its own kind, in
just the proportions that each needs: and so on
throughout all the various structures of the animal
economy.  These are all separate little functions.
  The blood is simply a carrier of the food
from which all the elements of the body derive
their sustenance; but it does not perform the
multiple function to select, for the many cells of
various kinds, their individual complex require-
ments.  Each individual cell possesses the power
to select by its polar forces that which it requires;
and these forces are generated and sustained by
nerve-impulse.
  Each separate and individual part or organ of
the animal economy has some special place or
center in the nervous system that presides over it;
some specific center where is generated the
motive-force that performs the function of the
part over which it has control; and the manner in
which the part does its work determines for us
the condition of its motive center.  A very few
of these nerve-centers have been located; yet a
sufficient number to assure us that each function
has, somewhere in the nerve-centers, a special
place that is generating and sending forth that
force which does the work.
  We may look upon the brain as a series of
dynamos that are constantly generating motive-

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force, and sending it out over the various con-
ductors that we call nerves, which convey it to
the place where the work is done.  This force
polarizes the cell structure, which then performs the
work of attraction and repulsion.

	[drawing of the brain]

  When the liver, kidneys, heart and other
organs continue to perform their various offices in
a healthy manner, the inference is that the motive-
forces are being furnished accordingly; but,
whenever any of these organs begin to perform
unnatural offices--generating abnormal secretions
such as sugar, uric acid, etc.--we infer that abnor-
mal motive impulses have supervened.
  NORMAL SECRETIONS ARE THE OUTCOME OF NOR-
MAL FUNCTIONS PERFORMED BY NORMAL IMPULSES.
  ABNORMAL SECRETIONS ARE THE OUTCOME OF

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ABNORMAL FUNCTIONS PERFORMED BY ABNORMAL
IMPULSES.
  Each class of secretions is dependent on its
characteristic motive-force.  In other words,
when a function becomes abnormal, it is not the
part or engine that is at fault, it is always the
motive-impulse which is responsible for the
erratic work.  For, even if the part itself through
local irritation or injury, is caused to change its
action, it even then does it by first sending the
irritation to the presiding nerve-center, which
reflects the impulse that causes the change.
  When a bone is broken, the first natural, local
changes that follow are pain and inflammation,
which occur as follows:  From the point of irri-
tation caused by the fracture, an impulse is sent
to the nerve-centers that preside over the part.
They return their characteristic impulses to the
place of injury, which at once establishes an
inflammatory action at the place of rupture; and
this action involves the manufacture or formation
of those products or elements needed to repair or
heal the part.  These are new, temporary func-
tions.  Without this communication from the
injury to the nerve-centers and the corresponding
return current, the fractured ends would never
become reunited nor the injury repaired.
  I have in mind a case of a railroad employe
who was under my care some twenty-five years

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ago.  Both bones in the lower part of the leg
were broken and protruded through the skin.  The
fractured ends were properly adjusted.  In a gen-
eral way, he was an unhealthy man, with a very
weak nervous system.  After several days, the
patient remarked to me, "I think you are a very
good doctor for I have no pain in my leg."  I
said, "My dear fellow, that is just what does not
suit me.  I prefer that you should have some
pain and inflammation."  But it did not follow.
For one hundred and forty days, I tried all the
various methods known to get up an irritation in
the part, after which I first discovered symptoms
of the broken ends reuniting themselves.  In this
case, the delay resulted from the weak condition
of the nerve-centers and their inability to respond
by sending back to the injured part the proper
nerve-impulse to establish inflammatory ac-
tion of repair.  Never can work or function be
performed without the appropriate application of
some motive-force to perform it.
  However brilliant an inventive genius may be
in all other directions, he begins to lose his reason
when he searches for perpetual motion, or a
piece of machinery so constructed as to possess
in itself the power to do the work or perform the
function.  Such an unfortunate genius generally
ends his life in a lunatic asylum.  As in mechanics,
so in animal life, all effects have a cause.





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        | End of Chapter II |  pages 17-23
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