Through the vital breath called Prana, a living creature is capable of moving about. Through that called Vyana they act. That called Apana goes downward. That called Samana lives within the heart.
प्राणात् प्रणीयते प्राणी व्यानाद् व्यायच्छतेतथा। गच्छत्यपानोऽधश्चैव समानो हृद्यवस्थितः॥