It will be simpler, and will answer the purpose equally well, to combine the third and fourth elements, and to consider as one element the idea of the movement and the fiat of will to execute the movement. _The Idea of a Movement_ The mental picture of a purposed movement is simple and direct. No reference is involved to the muscles concerned in the performance of the movement. When you will to raise your hand, the action is pictured to your mind as the raising of the hand, and nothing more. Certain muscles are to be contracted. But the mental picture of the movement does not indicate what these muscles are, in what order they are to be brought into play, nor the relative degrees of strength to be exerted by each muscular fiber. You do not consciously direct the muscles in their contractions. _The Discharge to the Muscles of the Nerve Impulse_ How then are the muscles informed that their contraction is called for? They have no independent volition; each muscular fiber obeys the impulse transmitted to it by the nerve, from the nerve center governing its action. These nerve centers are in their turn controlled by the central nervous mechanism. And in complex voluntary movements the central nervous mechanism is under the control of the higher cerebral centers. The wish to raise the hand appears to the mind as an idea of the hand being raised. This idea is translated by the central nervous mechanism into a set of motor nerve impulses. Does consciousness or volition come into play here? Not at all. On this point Prof. Ladd remarks: "As to the definite nature of the physical basis which underlies the connection of ideas of motion and the starting outward of the right motor impulses, our ignorance is almost complete." Is it necessary for the performance of a complex muscular action that the individual know what muscles are involved and how and when to contract them? No; this knowledge is not only unnecessary, it is even impossible. Prof. Ladd says of this: "It would be a great mistake to regard the mind as having before it the cerebral machinery, all nicely laid out, together with the acquired art of selecting and touching the right nervous elements in order to produce the desired motion, as a skilful player of the piano handles his keyboard."