contained the _motor cells_ through which impulse is translated to action.
These motor cells are controlled by _inhibitory cells_, which act as brakes
and release nerve energy in a gentle stream; otherwise our movements would
be convulsive in their violence, and life would be impossible through
inability usefully to direct our energy.

That is how inhibition acts physically; mentally it is the power to
restrain impulses until reason has suggested the wisest course.

Irritation of the cortex, especially the motor area, causes convulsions,
and experiment has shown that epilepsy may be due to a disease or
instability of certain inhibitory cells of the cortex. The motor cells of
epileptics are restrained, with some difficulty, by these cells in normal
times. When irritation from any cause throws additional strain on the motor
cells, the defective brakes fail, and the uncontrolled energy, instead of
flowing in a gentle stream through the usual channels, bursts forth in a
tidal wave through other areas of the brain, causes unconsciousness, and
exhausts itself in those violent convulsions of the limbs which we term a
fit.

The Primary Cause of epilepsy is an inherent instability of the nervous
system.

Secondary Causes are factors which cause the first fit in a person with
predisposing nervous instability; later, the brain gets the _fit habit_,
and attacks recur independently of the secondary cause. In most cases no
secondary causes can be discovered, and the disease is then termed
_idiopathic_, for want of an explanation.

Injuries to the brain may cause epilepsy, and many cases date from birth, a