THE FOOD AND DIGESTION 381 



scribed, they are frequently, when taken in the food, in an 

 unfavourable state for the action of digestive juices. Thus, 

 while the proteids of flesh are exposed to the gastric and 

 pancreatic secretion, the proteids of many vegetables, unless 

 carefully prepared, cooked, and masticated, are protected and 

 escape digestion and absorption. The same may be said of 

 the crude starch of vegetables. The digestibility and value 

 as an article of diet of the cellulose and allied substances in 

 plants is an important question at present requiring further 

 investigation. 



The fats of vegetables are also generally in a less favourable 

 state for digestion than the fats of animals. 



When once digested there seems to be no difference in the 

 absorbability and assimilability of the proximate principles 

 of vegetables and animals ; a given weight of vegetable pro- 

 teid may be substituted for the same quantity of animal 

 proteid. 



As a result of the difference in digestibility the availa- 

 bility of food-stuffs varies. The following table serves to 

 show some of these variations. 



Absorption of Food-stuffs. 



Per Cent. Absorbed. 

 Proteid. Fat. Carbohydrate. 



Flesh ... 97 95 



Egg .... 97 95 



Milk .... 89-99 96 100 



Bread ... 78 ... 99 



Potatoes (boiled) . 68 ... 92 



Carrots (raw) . .61 ... 82 



The availability of almost any article of food varies with 

 the state of the teeth and the digestive organs of the 

 individual, with the manner in which it is eaten whether 

 leisurely or too rapidly and without proper mastication, and 

 with the manner in which it is prepared. For example, the 

 mode of manufacture of the flour used in bread-making 

 has a very marked influence upon the amount digested and 

 absorbed. In vegetable foods especially the thoroughness 

 of the cooking has a most important influence on the availa- 

 bility of their constituents. 



