Because of the prominent place occupied by fatigue in thus being responsible for our diminished output, we shall briefly consider its place in study.  Everyone who has studied will agree that fatigue is an almost invariable attendant of continuous mental exertion.  We shall lay down the proposition at the start, however, that the awareness of fatigue is not the same as the objective fatigue in the organs of the body.  Fatigue should be regarded as a twofold thing—­a state of mind, designated its subjective aspect, and a condition of various parts of the body, designated its objective aspect.  The former is observable by introspection, the latter by analysis of bodily secretions and by measurement of the diminution of work, entirely without reference to the way the mind regards the work.  Fatigue subjectively, or fatigue as we feel it, is not at all the same as fatigue as manifested in the body.  If we were to make two curves, the one showing the advancement of the feeling of fatigue, and the other showing the advancement of impotence on the part of the bodily processes, the two curves would not at all coincide.  Stated another way, fatigue is a complex thing, a product of ideas, feelings and sensations, and sometimes the ideas overbalance the sensations and we think we are more tired then we are objectively.  It is this fact that accounts for our too rapid giving up when we are engaged in hard work.

A psychological analysis of the subjective side of fatigue will make its true nature more apparent.  Probably the first thing we find in the mind when fatigued is a large mass of sensations.  They are referred to various parts of the body, mostly the part where muscular activity has been most violent and prolonged.  Not all of the sensations, however, are intense enough to be localizable, some being so vague that we merely say we are “tired all over.”  These vague sensations are often overlooked; nevertheless, as will be shown later, they may be exceedingly important.

But sensations are not the only contents of the mind at time of fatigue.  Feelings are present also, usually of a very unpleasant kind.  They are related partly to the sensations mentioned above, which are essentially painful, and they are feelings of boredom and ennui.  We have yet to examine the ideas in mind and their behavior at time of fatigue.  They come sluggishly, associations being made slowly and inaccurately, and we make many mistakes.  But constriction of ideas is not the sole effect of fatigue.  At such a time there are usually other ideas in the mind not relevant to the fatiguing task of the moment, and exceedingly distracting.  Often they are so insistent in forcing themselves upon our attention that we throw up the work without further effort.  It is practically certain that much of our fatigue is due, not to real weariness and inability to work, but to the presence of ideas that appear so attractive in contrast with the work in hand that we say we are