will, every motion of a muscle, uses up a certain amount of what
we call nerve force, which is really a form of prana. To move a muscle
the brain sends out an impulse over the nerves, and the muscle
contracts, and so much prana is expended. When it is remembered that
the greater portion of prana acquired by man comes to him from the air
inhaled, the importance of proper breathing is readily understood.

CHAPTER V.

THE NERVOUS SYSTEM.

It will be noticed that the Western scientific theories regarding the
breath confine themselves to the effects of the absorption of oxygen,
and its use through the circulatory system, while the Yogi theory also
takes into consideration the absorption of Prana, and its
manifestation through the channels of the Nervous System. Before
proceeding further, it may be as well to take a hasty glance at the
Nervous System.

The Nervous System of man is divided into two great systems, viz., the
Cerebro-Spinal System and the Sympathetic System. The Cerebro-Spinal
System consists of all that part of the Nervous System contained
within the cranial cavity and the spinal canal, viz., the brain and
the spinal cord, together with the nerves which branch off from the
same. This system presides over the functions of animal life known as
volition, sensation, etc. The Sympathetic System includes all that
part of the Nervous System located principally in the thoracic,
abdominal and pelvic cavities, and which is distributed to the
internal organs. It has control over the involuntary processes, such
as growth, nutrition, etc.

The Cerebro-Spinal System attends to all the seeing, hearing, tasting,
smelling, feeling, etc. It sets things in motion; it is used by the
Ego to think--to manifest consciousness. It is the instrument with
which the Ego communicates with the outside world. This system may be
likened to a telephone system, with the brain as the central office,
and the spinal column and nerves as cable and wires respectively.

The brain is a great mass of nerve tissue, and consists of three
parts, viz., the Cerebrum or brain proper, which occupies the upper,
front, middle and back portion of the skull; the Cerebellum, or
"little brain," which fills the lower and back portion of the skull;
and the Medulla Oblongata, which Is the broadened commencement of the
spinal cord, lying before and in front of the Cerebellum.

The Cerebrum is the organ of that part of the mind which manifests
itself in