heir spectacles. So long as such movements are unconscious, they
facilitate the mental actions. At least this seems a fair inference from
the fact that confusion frequently results from putting a stop to them:
witness the case narrated by Sir Walter Scott of his school-fellow, who
became unable to say his lesson after the removal of the
waistcoat-button that he habitually fingered while in class. But why do
they facilitate the mental actions? Clearly because they draw off a
portion of the surplus nervous excitement. If, as above explained, the
quantity of mental energy generated is greater than can find vent along
the narrow channel of thought that is open to it; and if, in
consequence, it is apt to produce confusion by rushing into other
channels of thought; then by allowing it an exit through the motor
nerves into the muscular system, the pressure is diminished, and
irrelevant ideas are less likely to intrude on consciousness.

This further illustration will, I think, justify the position that
something may be achieved by pursuing in other cases this method of
psychological inquiry. A complete explanation of the phenomena, requires
us to trace out _all_ the consequences of any given state of
consciousness; and we cannot do this without studying the effects,
bodily and mental, as varying in quantity at each other's expense. We
should probably learn much if we in every case asked--Where is all the
nervous energy gone?

[1] _Macmillan's Magazine_, March 1860.

[2] For numerous illustrations see essay on "The Origin and Function of
Music."

ON THE ORIGIN AND FUNCTION OF MUSIC[1]

When Carlo, standing, chained to his kennel, sees his master in the
distance, a slight motion of the tail indicates his but faint hope that
he is about to be let out. A much more decided wagging of the tail,
passing by and by into lateral undulations of the body, follows his
master's nearer approach. When hands are laid on his collar, and he
knows that he is really to have an outing, his jumping and wriggling are
such that it is by no means easy to loose his fastenings. And when he
finds himself actually free, his joy expends itself in bounds, in
pirouettes, and in scourings hither and thither at the top of his speed.
Puss, too, by erecting her tail, and by every time raising her back to
meet the caressing hand of her mistress, similarly expresses her
gratification by certain muscular actions; as likewise do the parrot by
awkward da