Before going on to that topic we have a word to say about nervous fatigue. We mentioned the fact in Chapter VII that much of our actual feeling of fatigue is nervous rather than muscular. Not as much is known about nervous fatigue as about the fatigue that comes on when the muscles are overworked. One thing that seems pretty evident is that the place where the fatigue actually is located is in the very delicate nerve junctions. These junctions offer some resistance to the passing of nervous disturbances over them, and if they are compelled to submit too often to this passing they appear to offer still more resistance; in other words, to become fatigued. We must remember that the nerve junctions are exceedingly delicate things, consisting, as they do, of the interweaving of the almost inconceivably tiny featherings at the tips of sensory or connecting nerve cells with the equally tiny featherlike branches from the cell bodies of connecting or motor nerve cells. It is likely, also, that on account of their delicacy they are easily affected by the waste products that may be circulating about in the blood stream from the active muscles. In either case, the way to recover from nervous fatigue is simply by resting. It is not hard for the delicate nerve junctions to throw off fatigue if given a chance. The way to give them this chance is not to use them. As we shall see in the next chapter, mental processes are made up of nervous disturbances passing here and there in the brain. If we allow ourselves to be occupied too continuously with the same lines of thought, we are evidently sending nervous disturbances over the same nerve junctions over and over again. In order to give those nerve junctions a chance to rest, what we have to do is to think about something entirely different. The word that best expresses what we have in mind is “diversion.” In the strict sense diversion means a turning aside from what we have been doing to something different, and that is the best way to allow the brain to rest. The man who takes his business home with him, and dwells on it during the hours that are supposed to be set aside for rest, may be able to achieve more for the moment than if he were really to rest, although even that is doubtful; but in the long run there is no doubt that continuous efficiency depends on allowing the fatigued nerve junctions ample opportunity to recover, which means that the thoughts must be directed into entirely different channels. CHAPTER XI THE BRAIN AND COMPLEX NERVOUS ACTIONS