It should be emphasized that the nervous current, once started, always tends to seek outlet in movement.  This is an extremely important feature of neural action, and, as will be shown in another chapter, is a vital factor in study.  Movement may be started by the stimulation of a sense organ or by an idea.  In the latter case it starts from regions in the brain without the immediately preceding stimulation of a sense organ.  Howsoever it starts you may be sure that it seeks a way out, and prefers pathways already traversed.  Hence you see you are bound to have habits.  They will develop whether you wish them or not.  Already you are “a bundle of habits”; they manifest themselves in two ways—­as habits of action and habits of thought.  You illustrate the first every time you tie your shoes or sign your name.  To illustrate the second, I need only ask you to supply the end of this sentence:  Columbus discovered America in——.  Speech reveals many of these habits of thought.  Certain phrases persist in the mind as habits so that when the phrase is once begun, you proceed habitually with the rest of it.  When some one starts “in spite,” your mind goes on to think “of”; “more or” calls up “less.”  When I ask you what word is called up by “black,” you reply “white” according to the principles of mental habit.  Your mind is arranged in such habitual patterns, and from these examples you readily see that a large part of what you do and think during the course of twenty-four hours is habitual.  Twenty years hence you will be even more bound by this overpowering despot.

Our acts our angels are, or good, or ill,
Our constant shadows that walk with us still.

Since you cannot avoid forming habits, how important it is that you seek to form those that are useful and desirable.  In acquiring them, there are several general principles deducible from the facts of nervous action.  The first is:  Guard the pathways leading to the brain.  Nerve tissue is impressible and everything that touches it leaves an ineradicable trace.  You can control your habits to some extent, then, by observing caution in permitting things to impress you.  Many unfortunate habits of study arise from neglect of this.  The habit of using a “pony,” for example, arises when one permits oneself to depend upon a group of English words in translating from a foreign language.

Nerve pathways should then be guarded with respect to what enters.  They should also be guarded with respect to the way things enter.  Remember, as the first pathway is cut, subsequent nervous currents will be directed.  Consequently if you make a wrong pathway, you will have trouble undoing it.