The external organs of the body are used for external activities, but the inner ones are the instruments of the mind. The factors which are closer to the mind and which are more important for man than the physical organs are the centers which are located in the body, and the cleaner the channels of the breath are, the more active do the centers become. The breath is to these centers as the air is to the plants. Besides inner ablutions, the breathing practice itself cleanses the channels of the body.