Elements of the theory and practice of cookery

folds. When it is distended with food, this lining is stretched smooth. In it are the glands for secreting gastric juice, which converts proteids into the more soluble peptones. By the motion of the muscular wall, food in the stomach is churned up at the same time that the gastric juice mixes with it. As fast as it is reduced to the grayish pulp called chyme, the passage at the right-hand end of the stomach, called the pylorus (meaning gate)^ opens to let it out into the intestine, where two little ducts enter, one pouring in bile secreted by the liver and stored in the gall-bladder till needed, the other, pancreatic juice from the pancreas. This juice contains three ferments (p. 128): amylopsin^ which acts like ptyalin, changing starch to sugar ; trypsm^ which carries on the work of digesting proteids, begun by pepsin ; and steapsin^ which splits fats into simpler compounds. 1 Bile seems to have no particular effect upon any foodstuff, but other digestive fluids are ob- served to work better when bile is present. The small intestine itself yields a digestive fluid, of which little is known except that it changes maltose and cane-sugar to grape-sugar (glucose), in which form they are ab- sorbed. The whole mass of food, when ready for absorption, is a creamy fluid termed chyle. 326. Absorption of food from the alimentary canal. — The process of absorption is wonderfully interesting, but as the cooking of food has no direct connection with its absorption, that topic lies outside the scope of this text-book. Cooking prepares food for digestion; digestion prepares it for absorption. Some food is absorbed into the blood through the walls of the stomach, but more from the small intestine. It is sup- posed that the molecules of which foodstuffs are com- 1 For more about the digestion of fat, see p. 215. 198 THEORY AND PRACTICE OF COOKERY posed, particles far too small to be discerned by the microscope, are, by the digestive ferments, actually split into smaller molecules, so that they may pass through the lining membrane of the alimentary canal. It is to give ample surface for absorption that the small intestine is so long — twenty-six feet — and that its inner surface is thrown into folds and covered with tiny threadlike projections called villi (singular villus) that suck from the river of chyle all that is nutritious, and send it on into the blood stream, leaving waste matter to pass into the large intestine, and be expelled from the body. We may think of the alimentary canal as a water- course, at first straight, then widening into a lake or basin, then narrowing to a winding stream and receiv- ing tributaries, and, at last, having its current diverted into innumerable channels to irrigate the land through which it flows. Hi Peptones formed ; milk curdled. (Food made acid.) Food leaves stomach in grayish semi- liquid mass — chyme. More sugar formed. Peptones and simpler com- pounds formed. Fats split into simpler com- pounds and partly emulsi- fied. Grape-sugar formed. 11 IP II 11. all 111 §g.S 1! 1 GO i| is 2 • S *? «5 fee a 1 till 1. g 1 - ^ ^ - 1 «2 nil J ^ <»■ CO ' 1 i 1 ill 0^ o~.S ii 03 > 1 .1 « 1 S3 pq i^3