Sometimes the stomach, if it is in a healthy state, will retain some food for nearly fifteen or twelve hours; it depends on the quality of the food regarding lightness or coarseness. The presence of food in the stomach is indicated by the presence of its taste in the mouth and when belching. The retention of food in the stomach is due only to the slowness of digestion and continues until the food is digested, and its downward movement is due to the pressure of the expulsion force, which acts when digestion is completed. The expelling force is driven by, for example, the burning of sour yellow bile or black bile or one of the reasons that we will mention shortly. It is not true, although some people think so, that the whole reason food is retained in the stomach is the narrowness of the lower passage. If this were so, the swallowed dirham or dinar could not come out, wine and milk would not linger in the stomach and they would not float up in a weak stomach, causing rumbling and bloating. On the contrary, the reason for the natural descent of food is the digestion and ability of the stomach to expel food, and there is no great connection here with other reasons depending on the quality of the food, unless damage has occurred in the stomach.
Until the food is digested, the healthy stomach covers it, and its lower passage is greatly narrowed. When the time comes to expel the food, it expands and the stomach expels the food it contains through the action of its transverse fibers. “Whenever digestion speeds up, the descent of food speeds up, and when it slows down, the descent also slows down, unless some already known cause occurs that causes the food to come down from the stomach, although it has not yet been digested. The average length of time food remains in stomach until it comes out from twelve to twenty-two hours. If there is too much food and it is not digested due to its abundance or poor quality, then in both of these cases it does not remain for the proper time in a healthy stomach, which has great expelling power, but quickly rushes down and sometimes causes diarrhea and haida. And if the stomach is weak and the food burdens it, or ulcerated, covered with pimples, or has viscous juice in it that causes slipping, then the food is retained only for a short time, no matter whether the holding power or the digestive power is weakened. You can find out the signs and reasons for this, which you should know from what was said earlier in the preceding paragraphs.
Treatment for those whose food descends slowly from the stomach or those whose food floats up in the stomach. One of the therapeutic measures against this is sleeping on the right side; it promotes the descent of food from the stomach, although it does little to help digestion. Digestion is promoted by moderate walking, rubbing both legs and breaking the winds with the means taught in the corresponding paragraph.
Treatment for those whose food quickly leaves the stomach. Some ancient doctors called such people “stomachs,” but later the name “stomach” began to be used for another disease. One of the proven remedies for such patients is the use of a medicinal dressing with fenugreek flour, flaxseed and honey, as well as taking this medicine in a drink. This also includes the following remedy: take the yolk of a baked egg, a spoonful of honey and two danaks of grated mastic, collect all this in an egg shell and bake it in hot ashes, constantly stirring the mixture until it reaches, after which it is eaten. This remedy is used for three days. In general, in this case, before meals, you should take astringent medicines, cold if your nature is hot, and mixed with hot ones if your nature is cold; you already know all these medicines. The patient should sleep after eating, not move and not exercise at all; his upper limbs must be bandaged.