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 intellectual action.  The Cerebellum regulates the movements of the voluntary muscles.  The Medulla Oblongata is the upper enlarged end of the spinal cord, and from it and the Cerebrum branch forth the Cranial Nerves which reach to various parts of the head, to the organs of special sense, and to some of the thoracic and abdominal organs, and to the organs of respiration.

The Spinal Cord, or spinal marrow, fills the spinal canal in the vertebral column, or “backbone.”  It is a long mass of nerve tissue, branching off at the several vertebrae to nerves communicating with all parts of the body.  The Spinal Cord is like a large telephone cable, and the emerging nerves are like the private wires connecting therewith.

The Sympathetic Nervous System consists of a double chain of Ganglia on the side of the Spinal column, and scattered ganglia in the head, neck, chest and abdomen. (A ganglion is a mass of nervous matter including nerve cells.) These ganglia are connected with each other by filaments, and are also connected with the Cerebro-Spinal System by motor and sensory nerves.  From these ganglia numerous fibers branch out to the organs of the body, blood vessels, etc.  At various points, the nerves meet together and form what are known as plexuses.  The Sympathetic System practically controls the involuntary processes, such as circulation, respiration and digestion.