the body has been starved of oxygen and deprived of
sunlight, if the whole system has been kept on the rack, whether in the
sweatshop, or in the furnace of affliction, what is the effect on the
nervous system? Just what might have been expected. The sense-organs
shy, like a frightened horse, at every shadow or fluttering leaf. The
conducting wires break, and cross, and tangle in every imaginable
fashion. The central exchange, half wild with hunger, or crazed with
fatigue-toxins, shrieks out as each distorted message comes in, or sulks
because it can't understand them. And then, with charming logicality, we
declare that such an one is "all nerves."

The brain, by which we mean the biggest one near the mouth,--we have
little brains, or _ganglia_ all over our bodies,--so far from being an
absolute monarch, is not even a constitutional one, or a president of a
republic, but a mere house of congress of the modern type, which can do
little but register and obey the demands of its constituents. The brain
originates nothing. Impulses are brought to it from the sense-organs by
the nerves. They set up in it certain vibrations, or chemical
disturbances. It responds to these much as blue litmus paper turns red
when a weak acid is dropped on it, or as lemonade fizzes when you put
soda in it. If more than one of these vibrations are set up
simultaneously, it "chooses" between them, by responding to the
strongest. If the response differs from the stimulus, it is because of
its huge deference to precedent as established by the records of
previous stimuli with which its tissues are stored.

This brings us to the interesting and important question, What are the
causes of these disturbances of the nerve-tissues? Probably the most
important single result that has been reached in our study of nervous
diseases in the last fifteen years, is that the cause of them in easily
eighty per cent of all cases _lies entirely outside of the nervous
system_.

The stomach burns, the nerve-tissues send in the fire alarm and order
out the engines. The liver goes on a strike, and the body-garbage, which
it has failed to burn to clean ashes and clear smoke, poisons the
nerve-cells, and they remonstrate accordingly, on behalf of the other
tissues. The heart, or blood-vessels, fails to supply a certain muscle
with its due rations of blood and the nerves of the region cry out in
the agony of cramp.

We have discovered, by half a century of careful study in