Take the body, for example. The body derives its vital force from the Sun. There are five types of Pranas (life-breaths). These are known as Prana, Apana, Vyana, Udana and Samana Vayus. (Prana Vayu is the life-wind or vital air, which has its seat in the lungs; Apana Vayu is the life-wind that goes downwards and out at the anus; Samana Vayu is the vital air which has its seat in the cavity of the navel; Vyana Vayu is the life-wind which is diffused through the whole body; Udana Vayu is the life-wind which rises up the throat and enters the head). The Prana (life-breath) comes from the Sun. the Vyana comes from Vayu (air). The Apana comes from the earth. Udana comes from Agni (fire). The Samana comes from Akasha (space). Because of these five breaths functioning in us, we are able to live healthily. There are 72,000 blood vessels in a human being. The Vyana Vayu blows through the entire circulatory system. The Vyana Vayu is derived from Vayu (air). When the air is polluted, the 72,000 blood vessels get polluted and the effect of this on the Apana Vayu leads to cancer and heart attacks.
Man needs pure Vyana Vayu for good health. Students should realise the importance of maintaining the purity of the environment and developing a pure heart in the interests of their body and mind. Some kind of cleaning powder is used for cleaning vessels. Similarly prayer is the means of cleansing the heart. Through a pure heart one achieves spiritual insight. Impure minds are the cause of many heart troubles. When the heart is filled with all kinds of worldly desires, there is no room in it for spiritual effort. (SSS Vol.16, pp. 73-74)
When a living being sleeps, the five vital airs, life breath, downward air, diffused air, upward breath, digestive air (Prana, Apana, Vyana, Udana, Samana) - do function along with the five fires in the body conferring warmth. During sleep, inhalation and exhalation of the breath proceed serenely and evenly (samana). The Prana, the life breath acts like the consecrated fire (ahavaniya) perpetually burning in the household of a Vedic rite. It energizes us in the same steady manner.
The diffused air or Vyana is as the fire lit on the southern side (dakshinagni) of the altar in the Vedic rite. The upward breath, Udana, helps the mind reach the world of Brahman (Brahma-loka), which the person has earned the right to attain by their karma. In other words, it enables the person to experience the taste of mergence with the Supreme. For the embodied Atma (jiva) rests in sleep, is happy during sleep, is refreshed by sleep, and derives bliss while sleeping.
The embodied Atma is the deity enshrined in the body, its temple. The individual soul experiences all that is seen, heard, and contacted by the mind in the outer world, as well as the impact of all that it cannot see, hear, or contact by the mind. Besides these, the individual soul might construct and experience in dreams and witness experiences undergone during previous lives. It depends on the activities stamped on the mind of each one. Or, it might happen sometimes that the person gives up at one stroke the association with the body and the senses and gets immersed and lost in their basic principle: the Omniself (Paramatma). The bliss that fills the individual soul is the manifestation of the supreme Self (Paramatma).
During dreamless sleep, the individual soul (jiva) enters and revels in the region of bliss (ananda loka), led thereto by the splendour of the upward breath, the vital air that elevates. The region of bliss is known also as the region of Brahma (Brahma-loka). During sleep, one effortlessly gets this splendid chance to enjoy the proximity of the supreme Atma, which is the prime source and substance of the five basic elements, the five senses, and the inner instrument of awareness (the five bhuthas, the five indriyas, and the antahkarana). But this experience is quite temporary and doesn t last.
The person who has gained awareness through the purification of the mind and the clarification of the intellect (buddhi) will have the unchanging bliss of mergence in the supreme Atma. Only that person can become omniscient who is ever in the region of the undecaying (akshaya) and merged in the imperishable (akshara) supreme Vastness (Parabrahma), the highest Atma. When one is aware that all is He, that there is nothing without or outside, one becomes all or Brahman.
In deep sleep, the individual soul (jiva) is in dull ignorance (in the tamo guna). To the realised person, however, even dreams will award as much bliss as does the consciousness while awake. Even when awake, the realised person gets rid of the impact of the body-sensereason complex and is saturated with the bliss of his authentic reality. The particularized self shares the consciousness (chaitanya) of the Universal, and it can merge only in that supreme Atma (Paramatma), the supreme Consciousness. Therefore, this aphorism emphasizes for us the truth that the ‘Is-ness (Sat)’, which ‘becomes’ and ‘subsumes’ all creation, refers only to the highest Brahman (Parabrahman), the supreme Consciousness, and not to any entity derived from it and dependent on it. (Sutra Vahini, pp. 51-53)