This deals with the digestive system of the body. To survive, every individual must have a perfect metabolic system. Agni, also known as Pitta, is the digestive system of the human body. Charaka thus described Agni as the 'Mool'(basis) of life. Sweet, Sour, Salty, Bitter, Pungent and Astringent are the 6 rasas produced, on digestion of food. The food that is not digested is known as 'Ama'.

	Bhutagnis	:	There are 5 Bhutagnis in our body. They are 'Akasha'(akashagni), 'Vayu'(vayawagni), 'Tej'(tejagni), 'Jala'(jalagni) and 'Prithvi'. All of them individually digest the food inside them. Aiding them is a form of heat that is present in the tissues.
	Dhatuagni	:	Deals with a much wider aspect than digestion. It is in actuality a biochemical process, including anabolic and catabolic activity. There are 7 Dhatuagni. The Saptadhatus of the body have within them, their own Agni. They look after digestive and nourishment process.
			According to Sushruta, Agni is similar in nature to Pitta, due to both of their 'firy' nature. The Dhatuagni are 'Rasa'(rasagni), 'Rakta'(raktagni), 'Mamsa'(mamsagni), 'Meda'(medagni), 'Asthi'(asthyagni) and 'Majja'(majjagni).
	Pachakagni	:	Also known as Jatharagni, it is responsible for the basic digestion system. The others, Bhutagni and Dhatuagni, depend on Pachakagni for proper functioning. If therefore, Pachakagni's performance is hampered in any manner, the others will be affected as well.
			There are four states of Pachakagni.
	Samagni	:	The food that is ingested is digested with it's help. The health condition is said to be perfect.
	Mandagni	:	It occurs when the individual intakes food that has Kapha. The symptoms are fullness of stomach, among others. This occurs due to failure of the Agni to digest food on schedule. The majority of human ailments are due to Mandagni.
	Tishnagni	:	When heavy food is digested in a very short time, there are different anomalies in the body. There is giddiness, thirst, eruptions and burning sensation. Usually associated if the intake of Pitta is abnormally high.
	Vishamagni	:	When the body is faced with irregular digestive problems, Vishamagni is to be blamed. Constipation, Abdominal colic and gas problems, are it's symptoms. It occurs when Vata producing substances are taken in high quantity.