Astanga Hrudaya
तदधिष्ठानमन्नस्य ग्रहणाद्ग्रहणी मता। सैव धन्वन्तरिमते कला पित्तधराह्वया॥५०॥
Jatharagni fire in the stomach and duodenum which aids digestion of food: Its (pacaka pitta vis a vis jatharagni) seat is grahani duodenum) so called because it withholds the food (for a certain time inside the amasaya i.e. stomach to facilitate digestion) in the opinion of Dhanvantari it is the kala known as Pittadhara situated at the entrance of the pakvasaya (intestines)
english translation
tadadhiSThAnamannasya grahaNAdgrahaNI matA। saiva dhanvantarimate kalA pittadharAhvayA॥50॥
hk transliteration by Sanscript