HOME ECONOMICS AND EDUCATION 551 



again to the alimentary canal mainly in the digestive juices that 

 are needed for digesting the food. The material thus removed from 

 circulation and returned to the alimentary canal, which consists of 

 so-called metabolic products, is excreted with the undigested residue 

 in the feces. The remainder of the food taken into the circulation 

 represents the amount retained by the body for building material 

 ind for fuel. The difference between the food which is absorbed 

 juid that which the body secures, therefore, is represented by the 

 metabolic products. By the present methods of experimenting, 

 however, the portion of the feces that consists of metabolic products 

 can not be satisfactorily distinguished from the undigested residue. 

 It is very difficult, therefore, to determine the actual digestibility, 

 but comparatively easy to estimate the apparent digestibility of 

 food. The terms digestible, indigestible, etc., as here used refer 

 simply to the food which is or is not available for the general nour- 

 ishment of the body after the process of digestion is completed. In 

 common, however, they are used more loosely as referring to the 

 ease and quickness of digestion, and the general healthfmness of 

 food bread, for instance is spoken of as simple and digestible, 

 fruit cake, as rich and indigestible. There is often much practical 

 truth behind such statements, though little is definitely known con- 

 cerning the time or labor required to digest different kinds of food. 



Food does not ordinarily pass from the stomach into the intes- 

 tine until it has been reduced to a liquid or semi-liquid condition. 

 The amount and consistency of food have a marked influence on 

 the rate of digestion in the stomach. Fluids leave the stomach 

 more rapidly than other materials. Hot drinks do not leave the 

 stomach more quickly than cold ones, nor does the quantity have 

 much effect. Solid matter in solution or suspension delay the 

 passage of fluid from the stomach somewhat. The consistency of 

 solid foods seems to have more effect upon digestibility than the 

 amount consumed. The quantity eaten increases the length of time 

 the material remains in the stomach, but not proportionally. 



To select a few examples of the time required for foods to leave 

 the stomach: Two eggs (raw, poached, or in the form of an 

 omelet), 7 ounces sweetbreads, 10 moderate-sized oysters, 7 ounces 

 whitefish or 3^ ounces of white bread, cauliflowers, or cherries, each 

 left the stomach in from 2 to 3 hours. Eight and one-fourth ounces 

 of chicken, 9 ounces of lean beef, 6 ounces boiled ham, 3^ ounces 

 roast veal or beefsteak, 5 1-3 ounces of coarse bread, boiled rice, car- 

 rots, spinach, radish, or apple, left the stomach in 3 to 4 hours. 

 Nine ounces of smoked tongue, 3 l /2 ounces smoked beef, 9 ounces 

 roast goose, 5 1-3 ounces string beans, or 7 ounces peas porridge, 

 left the stomach in 4 to 5 hours. 



Generally speaking, the most readily digested animal foods 

 were materials of soft consistency. White meats for example, 

 chicken leave the stomach more quickly than red meats or dark 

 meat for instance, duck. The method of cooking also exerts a 

 very marked influence on stomach digestion. Fresh fish was foun4 

 to be more readily digested than meats, 



