Agni (fire) is the invariable agent in the process of Paka (chemical action).Ingested food is to be digested, absorbed and assimilated, which is unavoidable for the maintenance of life and is performed by Agni. The different types of Agni perform different functions according to its site. Wholesome food stuffs ingested in fourfold manner having been digested by Jatharagni is followed by further Paka by Bhautikagni which are again subjected further Paka by Dhatwagni. Dhatwagnis catalyse further metabolic transformation of the nutrient substances before they made available to the seven Dhatus. According to modern science, hormones and enzymes also act as catalyst in metabolic transformation similar to that of Dhatwagni in Ayurveda. This concept is helpful in understanding Samprapti (pathogenesis) of metabolic diseases like Prameha (diabetes), hypothyroidism and hence in planning line of treatment according to Ayurveda.

Keywords: Agni; Dhatu; Dhatwagni; Margaga Dhatu; Sthanastha Dhatu.