Now, investigation shows that the physical body, is a mechanism specially adapted for the transmutation of the inner or mental power into modes of external activity. We know from medical science that the whole body is traversed by a network of nerves which serve as the channels of communication between the indwelling spiritual ego, which we call mind, and the functions of the external organism. This nervous system is dual. One system, known as the Sympathetic, is the channel for all those activities which are not consciously directed by our volition, such as the operation of the digestive organs, the repair of the daily wear and tear of the tissues, and the like. The other system, known as the Voluntary or Cerebro-spinal system, is the channel through which we receive conscious perception from the physical senses and exercise control over the movements of the body. This system has its centre in the brain, while the other has its centre in a ganglionic mass at the back of the stomach known as the solar plexus, and sometimes spoken of as the abdominal brain. The cerebro- spinal system is the channel of our volitional or conscious mental action, and the sympathetic system is the channel of that mental action which unconsciously supports the vital functions of the body. Thus the cerebro- spinal system is the organ of conscious mind and the sympathetic is that of sub-conscious mind. But the interaction of conscious and subconscious mind requires a similar interaction between the corresponding systems of nerves, and one conspicuous connection by which this is provided is the "vagus" nerve. This nerve passes out of the cerebral region as a portion of the voluntary system, and through it we control the vocal organs; then it passes onwards to the thorax sending out branches to the heart and lungs; and finally, passing through the diaphragm, it loses the outer coating which distinguishes the nerves of the voluntary system and becomes identified with those of the sympathetic system, so forming a connecting link between the two and making the man physically a single entity. Similarly different areas of the brain indicate, their connection with the objective and subjective activities of the mind respectively, and speaking in a general way we may assign the frontal portion of the brain to the former and the posterior portion to the latter, while the intermediate portion partakes of the character of both.