genated blood is carried to all parts of the system, building up and replenishing, so is the prana carried to all parts of the nervous system, adding strength and vitality. If we think of prana as being the active principle of what we call "vitality," we will be able to form a much clearer idea of what an important part it plays in our lives. Just as is the oxygen in the blood used up by the wants of the system, so the supply of prana taken up by the nervous system is exhausted by our thinking, willing, acting, etc., and in consequence constant replenishing is necessary. Every thought, every act, every effort of the 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.
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
