Page:Food and cookery for the sick and convalescent.djvu/38

16

White Fish (Cod excepted) 2½ to 2¾ hours

Tapioca, Arrowroot, and Sago Gruel. . . 2⅔ "

Beef, roast, rare 3 "

Lamb Chops (3½ oz.). 3 "

Chicken 3 "

Game 3 "

Apple, large (raw) 3¼ "

Peas 4

Beans. .. 4 "

Digestion principally takes place in the small intestine. The stomach acts as a reservoir for food, playing but a small part in digestion. Many instances are recorded where people have been well nourished after the removal of the stomach. There was, however, a radical change in the diet, the food being taken in a liquid or semi-solid state.

Food in the small intestine comes in contact with two fluids,—the pancreatic juice and the bile (which is poured out from the liver), both of which are alkaline fluids. The flow of pancreatic juice is suspended except during digestion, while the flow of bile is constant but greatest during digestion.

The pancreatic juice contains four ferments,—amylopsin, trypsin, steapsin, and invertin.

Amylopsin acts upon starches and completes their digestion. Trypsin completes the digestion of proteids. Its action is similar to the action of pepsin in the gastric juice, but it is able to act in an alkaline medium. The proteids which were simply swollen in the stomach are now penetrated by this juice and their digestion is completed. Steapsin splits the fats into glycerine and fatty acids. The fatty acids combine with an alkaline solution and form soap. The bile salts also play an important part in the digestion of fats, but affect neither proteids nor carbohydrates. They, too, combine with fatty acids to form soap, and soap forms an emulsion. Fats thus emulsified are ready for absorption. Invertin acts upon cane sugar, changing it to levulose and dextrose.