Now this imitation of a fault in speech is subconscious and will not always right itself naturally, and the reason for this will become clear with a little consideration. Set a man to work on an elaborate and intricate piece of machinery. Tell him that if he moves a switch here and a lever there, certain effects will be produced and certain desired results obtained. The movements are simple ones, and the man left to himself will be able to control the working of the machine with ease and certainty. But let us suppose that some essential part of the machine is put out of gear, and that the machine instead of running smoothly and easily begins to jerk and hiccough. Our assumed operator is immediately at a loss. He sees that there is something wrong, and that there is obvious friction where there was ease before; noise has taken the place of silence; but he knows nothing of the working of the machine save the elementary movements of the switch and lever, in the uses of which he has had instruction. Now, he may perform these movements again and again; but the machine still stutters, and our operator, quite at a loss, can do nothing to obviate these faults. He must allow the machine to continue working badly if it works at all. The boy we have adduced as an example of a stammerer, who has copied some fault of another boy and found that fault become permanent, is in exactly the same position as the unskilled operator of our illustration. This boy knows the ordinary uses of his vocal machine which have heretofore produced normal results, but he does not know enough of the machine to repair it when it is put out of gear; he cannot control the machinery so that it may at once be restored to its previous efficiency. But just as the unskilled operator may be instructed in the complete mechanism he is set to supervise, and may then stop the machine when any fault becomes evident, discover the source of the defect and set it right; so will any person who has been instructed in the principles of conscious control be able to detect and obliterate any fault in his vocal or any other bodily mechanism, even if that fault was originated below the level of consciousness.