manifestations, and here, therefore, are at fault; because, although it
seems so much slighter a thing to think a little than to hit out with
the power of an athlete, it may prove that the expenditure of nerve
material is in the former case greater than in the latter.

When a man uses his muscles, after a time comes the feeling called
fatigue--a sensation always referred to the muscles, and due most
probably to the deposit in the tissues of certain substances formed
during motor activity. Warned by this weariness, the man takes rest--may
indeed be forced to do so; but, unless I am mistaken, he who is
intensely using the brain does not feel in the common use of it any
sensation referable to the organ itself which warns him that he has
taxed it enough. It is apt, like a well-bred creature, to get into a
sort of exalted state under the stimulus of need, so that its owner
feels amazed at the ease of its processes and at the sense of
_wide-awakefulness_ and power that accompanies them. It is only after
very long misuse that the brain begins to have means of saying, "I have
done enough;" and at this stage the warning comes too often in the shape
of some one of the many symptoms which indicate that the organ is
already talking with the tongue of disease.

I do not know how these views will be generally received, but I am sure
that the personal experience of many scholars will decide them to be
correct; and they serve to make clear why it is that men may not know
they are abusing the organ of thought until it is already suffering
deeply, and also wherefore the mind may not be as ruthlessly overworked
as the legs or arms.

Whenever I have closely questioned patients or men of studious habits as
to this matter, I have found that most of them, when in health,