to be on the other
side of it; or scramble up the bank for the sake of any thing that is on
the top of it; or run about to different places because we wish to be in
the places particularly. It is the internal force that is in us working
itself off, and it works itself off in the ways that come most readily to
hand."

_Various Modes in which the Reserved Force reappears_.

The force thus stored in the food and liberated within the system by
the vital processes, finds scope for action in several different ways,
prominent among which are, First, in the production of animal heat;
Secondly, in muscular contractions and the motions of the limbs and members
resulting from them; and Thirdly, in mental phenomena connected with the
action of the brain and the nerves. This last branch of the subject is yet
enveloped in great mystery; but the proof seems to be decisive that the
nervous system of man comprises organs which are actively exercised in the
performance of mental operations, and that in this exercise they consume
important portions of the vital force. If, for example, a child is actually
engaged at play, and we direct him to take a seat and sit still, he will
find it very difficult to do so. The inward force will soon begin to
struggle within him to find an issue. But if, while he is so sitting, we
begin to relate to him some very surprising or exciting story, to occupy
his _mind_, he will become motionless, and very likely remain so until the
story is ended. It is supposed that in such cases the force is drawn off,
so to speak, through the cerebral organs which it is employed in keeping in
play, as the instruments by which the emotions and ideas which the story
awakens in the mind are evolved. This part of the subject, as has already
been remarked, is full of mystery; but the general fact that a portion of
the force derived from the food is expended in actions of the brain and
nervous system seems well established.

Indeed, the whole subject of the reception and the storing up of force from
the sun by the processes of vegetable and animal life, and the subsequent
liberation of it in the fulfillment of the various functions of the animal
system, is full of difficulties and mysteries. It is only a very simple
view of the _general principle_ which is presented in these articles. In
nature the operations are not simple at all. They are involved in endless
complications which are yet only to a very limited extent unravelled.