Agni literally means fire. It represents a combustible force present inside each and every nook and cranny of the body such that the food may transform itself into bodily tissues and the bodily tissues may intermingle among themselves. Thus, it is the fire that brings about biochemical changes. While the function in comparison is pretty much adjunctive or exemplary of pitta; most “Acharyas” consider Agni to be one form of pitta. Agni thus is responsible for all the biochemical transformation happening in the body. So, an adept person would know to classify Agni according to the innumerability – in each and every cell of the body – it
Despite its innumerability, Charaka organized the concept of Agni into thirteen types. The main and singular entity called the Jatharagni (Jathara – Stomach and Duodenum, Agni – Fire) is the chief Agni. Each and every nutrient that one ingests first comes to the Jathara and is subjected to the action of Jatharagni. Jatharagni digests the food materials that consist of the five basic elements and transforms it for utilization by the respective tissues. Jatharagni is also responsible for the separation of the food material into the essence portion and the waste products in our body.
The Jatharagni also fuels the other twelve Agnis – which are classified into two types. The Dhatwagni (Dhatu – Tissues, Agni – Fire) which are seven in number and the Bhutagni (Bhuta – Elements, Agni – Fire) which are five in number are the collaborative Agnis which helps the Jatharagni in fully digesting the foods. The process of digestion begins with the Jatharagni acting on the food present in the stomach, which invariably converts all the food types into the Sara / Anna rasa (the part that is to be absorbed) and the Kitta /Mala (the part that is to be excreted).
The absorbed portion of the food gets acted on by respective Dhatwagni and the Bhootagnis, the Dhatwagni fosters the tissues, while the Bhootagni kindles the basic five elements of the body. The first Dhatwagni to act on the absorbed nutrients is the
The Bhootagni are five in number. The Prithviagni, Apagni, Tejasagni, Vayuagni, Navyagni disintegrate the food into the five elemental forms Earth, Water, Fire, Air, and Space and thus nourishing the respective portion and the senses that recognize them.
The Jatharagni based on its strength may again be categorized into Samagni, Visamagni, Tikshnagni, and Mandagni. The Samagni assimilates and digests the food at the proper amount and time. Thus, Samagni grants person hale. The Visamagni vacillates between the highs and low of Tikshnagni and Mandagni respectively. In Tikshnagni, the fire is kindled into an extensible force such that it begins to digest the bodily tissues to keep it lit. Thus the person invariably becomes thin. While in the processes of Mandagni the vice-versa holds true.