And when it was the turn of Kousalya, he put this question: “Master, of what is Prana born; how does he enter the body; how does he live there after dividing himself; how does he go out; how does he experience what is outside; and how does he hold together the body, the senses and the mind?”
To which the sage replied: “Kousalya, you ask very difficult questions; but since you are a sincere seeker after the truth of Brahman, I must answer. Prana is born of the Self. Like a man and his shadow, the Self and Prana are inseparable. Prana enters the body at birth, that the desires of the mind, continuing from past lives, may be fulfilled. As a king employs officials to rule over different portions of his kingdom, so Prana associates with himself four other Pranas, each a portion of himself and each assigned a separate function. The PRANA himself dwells in eye, ear, mouth, and nose; the APANA, which is the second Prana, rules the organs of excretion and generation; the SAMANA, which is the third Prana, inhabits the navel and governs digestion and assimilation. The Self dwells in the lotus of the heart, whence radiate a hundred and one nerves. From each of these proceed one hundred others, which are smaller, and from each of these, again, seventy-two thousand others, which are smaller still. In all these moves the VYANA, which is the fourth Prana. And then at the moment of death, through the nerve in the centre of the spine, the UDANA, which is the fifth Prana, leads the virtuous man upward to higher birth, the sinful man downward to lower birth, and the man who is both virtuous and sinful to rebirth in the world of men.
The sun is the Prana of the universe. It rises to help the Prana in the eye of man to see. The power of earth maintains the Apana in man. The ether between the sun and the earth is the Samana, and the all-pervading air is the Viyana. The Udana is fire, and therefore he whose bodily heat has gone out dies, after which his senses are absorbed in the mind, and he is born again. Whatever his thought at the moment of death, this it is that unites a man with Prana, who in turn, uniting himself with Udana and with the Self, leads the man to be reborn in the world he merits.”