{TCD 1299 page and line 29b54} Let it be asked here whether all digestion works through heat and dryness; it seems to be so, for Hippocrates says that cold is an enemy of nature, and digestion is its friend, so every {TCD 1299 page and line 30a1} digestive is hot and dry. Then Galenus says in De ingenio sanitatis these words: ‘Illud quod ... ’ i.e. everything that injures people in health, injures still more sick people, and cold injures people in health, so it injures still more sick people, if so, since digestion relieves well and sick, it is understood to be by heat. Then Avicenna says in the chapter on energies these words: ‘Frigidum non ... ’, i.e. cold does not enter into natural operations, and that is not the case in operations of the digestion, for it much benefits nature, so every digestive works by heat. This is opposed according to Galenus in De ingenio sanitatis, who says every digestive is contrary to the matter for which it is given, if so, since fever is hot and dry, the digestive for fever should be cold and moist. Then Avicenna says in the same chapter these words: ‘Aqua frigida ... ’ i.e. cold water helps digestion in subtle choleric matter, so digestion is caused by cold. Then Haly says in the first book of Techne that hot matter is digested by cold, so digestion is not caused by heat. Then Galenus says in De ingenio sanitatis that the compound called oxisacra should be given to digest the thick matter, and it is clear that oxisacra itself is cold, so digestion does not work by heat. Then Galenus says in the tenth book of De ingenio sanitatis these words: ‘Aquam frigidam ... ’ i.e. cold water induces perspiration and abdominal flux, so since the function of a digestive is to prepare the matter for expulsion, and since cold water does those things we have said, it is understood that digestion is not caused by heat. We answer this question and say that there are two conditions the physician must examine for digestion, i.e. the closeness or openness of the pores through which