I have chosen here as examples men whose brains are engaged constantly in the higher forms of mental labor; but the difficulty of arresting at will the overtasked brain belongs more or less to every man who overuses this organ, and is the well-known initial symptom of numerous morbid states.  I have instanced scholars and men of science chiefly, because they, more than others, are apt to study the conditions under which their thinking organs prosper or falter in their work, and because from them have we had the clearest accounts of this embarrassing condition of automatic activity of the cerebral organs.  Few thinkers have failed, I fancy, to suffer in this way at some time, and with many the annoyance is only too common.  I do not think the subject has received the attention it deserves, even from such thorough believers in unconscious cerebration as Maudsley.  As this state of brain is fatal to sleep, and therefore to needful repose of brain, every sufferer has a remedy which he finds more or less available.  This usually consists in some form of effort to throw the thoughts off the track upon which they are moving.  Almost every literary biography has some instance of this difficulty, and some hint as to the sufferer’s method of freeing his brain from the despotism of a ruling idea or a chain of thought.

Many years ago I heard Mr. Thackeray say that he was sometimes haunted, when his work was over, by the creatures he himself had summoned into being, and that it was a good corrective to turn over the pages of a dictionary.  Sir Walter Scott is said to have been troubled in a similar way.  A great lawyer, whom I questioned lately as to this matter, told me that his cure was a chapter or two of a novel, with a cold bath before going to bed; for, said he, quaintly, “You never take out of a cold bath the thoughts you take into it.”  It would be easy to multiply such examples.

Looking broadly at the question of the influence of excessive and prolonged use of the brain upon the health of the nervous system, we learn, first, that cases of cerebral exhaustion in people who live wisely are rare.  Eat regularly and exercise freely, and there is scarce a limit to the work you may get out of the thinking organs.  But if into the life of a man whose powers are fully taxed we bring the elements of great anxiety or worry, or excessive haste, the whole machinery begins at once to work, as it were, with a dangerous amount of friction.  Add to this such constant fatigue of body as some forms of business bring about, and you have all the means needed to ruin the man’s power of useful labor.