Mbh 3.212.1a

“The Brahmana enquired, ‘How is it that fire (vital force) in combination with the earthly element (matter), becomes the corporeal tenement (of living creatures), and how doth the vital air (the breath of life) according to the nature of its seat (the muscles and nerves) excite to action (the corporeal frame)?’ Markandeya said, ‘This question, O Yudhishthira, having been put to the Brahmana by the fowler, the latter, in reply, said to that high-minded Brahmana. (The fowler said):--The vital spirit manifesting itself in the seat of consciousness, causes the action of the corporeal frame. And the soul being present in both of them acts (through them). The past, the present and the future are inseparably associated with the soul. And it is the highest of a creature’s possessions; it is of the essence of the Supreme Spirit and we adore it. It is the animating principle of all creatures, and it is the eternal purusha (spirit). It is great and it is the intelligence and the ego, and it is the subjective seat of the various properties of elements. Thus while seated here (in a corporeal frame) it is sustained in all its relations external or internal (to matter or mind) by the subtle ethereal air called prana, and thereafter, each creature goes its own way by the action of another subtle air called Samana. And this latter transforming itself into Apana air, and supported by the head of the stomach carries the refuse matter of the body, urine &c, to the kidneys and intestines. That same air is present in the three elements of effort, exertion and power, and in that condition it is called Udana air by persons learned in physical science, and when manifesting itself by its presence at all the junctional points of the human system, it is known by the name Vyana. And the internal heat is diffused over all the tissues of our system, and supported by these kinds of air, it transforms our food and the tissues and the humours of our system.