In a famous book in its day, “History of a Mouthful of Bread,” by Jean Mace, republished in this country from the eighth French edition (1868), the author observes: “If your body were made of glass and you could watch your intestine at work, it would appear to you like a very long and large worm coiled into a bundle, moving and heaving with all its rings at once. You would never suspect there are such movements within you; yet they have been going on continuously since you were born.” Now we can actually watch these movements by eating meals containing substances that are opaque to the x-rays (like barium or bismuth). As such a meal progresses from the stomach through the intestine the shadow of the barium defines the outlines of the organ with which it is in contact. By this and other methods involving the use of the x-ray it has been shown that the small intestine in particular is constantly in involved, tortuous motion.
The old idea of digestion was that it was largely a function of the stomach. This is not correct. Von Mering’s experiments show that as soon as water is introduced into the stomach it begins to pass into the intestine by a series of spurts from the contractions of the stomach. Within a short time practically all the water swallowed can be recovered below the stomach, none or very little having been absorbed by that organ. Howell’s “Physiology” states the case very conservatively when it says absorption of food does not take place readily in the stomach, certainly nothing like so easily as in the intestine. Starling’s “Physiology” (1920) probably the leading English authority, says there is no absorption of water in the stomach, thus going a little further than Von Mering.
In passing from the stomach the contents, says Kellogg, are spurted some distance along the intestinal canal. The starches and sugars pass on most rapidly, next in order are the foods from animal sources (proteins) such as meat, cheese, eggs, etc., and lastly the fats. (This is a good place to note that these are the three classes of food: starches and sugars, carbohydrates; foods mainly of animal origin, protein; and fats.) Bread, continues Kellogg, begins to enter the small intestine within ten minutes after eating (providing, he says elsewhere, it is not too fresh and is well Cooked). Potato leaves the stomach rapidly, perhaps because it is acted upon in the stomach only to a very small extent. At the end of half an hour eight times as much carbohydrates have left the stomach as have proteins. Fat remains long and retards the passage of both carbohydrates and proteins when it is present in considerable amount (hence the undesirability of food fried in fat, much “shortening” in biscuit, pie crust, etc., which incorporated fat retards carbohydrate digestion). Where there is an excess of acid in the stomach fluids it delays progress of the meal by causing a prolonged closure of the discharging end of the stomach (pylorus), a fact that has relation to the use of vinegar as food’
Examination of the contents of the intestine in the duodenum (immediately below the stomach), which receives the contents of the stomach, and about 23 feet lower down at the valve separating the small from the large intestine (colon), shows that the products formed by digestion have largely disappeared in traversing this distance. All the information we possess indicates that the small intestine absorbs readily .
The prevailing idea of digestion is that it is largely a function of the stomach and that the stomach readily absorbs such things as the end products of protein food (peptones), sugar, salt, etc. Actual experiments, how-ever, says Howell, made under conditions as nearly normal as possible, show, upon the whole that absorption does not take place readily in the stomach. Von Mering and Brandl, quoted approvingly by our author, found that sugar of ordinary dilution and sugar farmed from the starchy foods of the ordinary meal, pass into the small intestine for further digestion and absorption. With a definite amount of protein introduced in the stomach of an experimental animal, it could all be recovered from an opening into the duodenum (the first intestinal section below the stomach), by a duodenal fistula (bringing the intestine outside through an artificial opening in the side) . So that the products of preliminary stomach digestion after being worked up in the lower end of the stomach are passed on in the form of a mildly-acid semi-fluid mixture called chyme, which is combined with pancreatic juice, bile and intestinal secretions. Thus real digestion begins in the duodenum.
It is an important matter to assist Nature to empty the stomach after a meal, especially where the stomach is weak (deficient motility). Upon lying down when it still contains food (the minimum emptying period being 3 1/2 hours) the patient should always lie upon the right side, thus lowering the discharging end of the stomach and bring gravity to the aid of the weakened organ. This is a wise precaution even with well people in the opinion of Kellogg.