The most obvious manifestation of this Prana in the human body is the motion of the lungs. If that stops, as a rule all the other manifestations of force in the body will immediately stop. But there are persons who can train themselves in such a manner that the body will live on, even when this motion has stopped. There are some persons who can bury themselves for days, and yet live without breathing. To reach the subtle we must take the help of the grosser, and so, slowly travel towards the most subtle until we gain our point. Pranayama really means controlling this motion of the lungs and this motion is associated with the breath. Not that breath is producing it; on the contrary it is producing breath. This motion draws in the air by pump action. The Prana is moving the lungs, the movement of the lungs draws in the air. So Pranayama is not breathing, but controlling that muscular power which moves the lungs. That muscular power which goes out through the nerves to the muscles and from them to the lungs, making them move in a certain manner, is the Prana, which we have to control in the practice of Pranayama. When the Prana has become controlled, then we shall immediately find that all the other actions of the Prana in the body will slowly come under control. I myself have seen men who have controlled almost every muscle of the body; and why not?