HYGIENE OF DIGESTION 249 



in preparing the meal at which they are to be eaten. 

 If oatmeal and other mushes are sticky, it shows the 

 presence of half-cooked starch. The yellow crust of 

 bread will not stick together because the starch has been 

 changed into the last stage of dextrin, called yellow dex- 

 trin. Rice and oatmeal may be first browned in the 

 oven and afterward steamed. Toast and brown crust 

 are almost as digestible as ripe fruit and are given to 

 invalids. 



449. Cellulose has the same chemical composition as 

 starch. It forms the cell walls and woody fibers of plants, 

 and is hardly digested at all by man ; hence, starch requires 

 cooking to burst the cellulose envelopes of the starch 

 grains. Cellulose and water are the chief constituents of 

 grass, and of greens, cabbage, and other fibrous vegetables. 

 It forms the fibers in watermelons, which also contain cane 

 sugar, the sweetest of the sugars. The woody skins of beans 

 and peas are cellulose. Hence, many find the legumes 

 more digestible in a puree, or cooked with the skins re- 

 moved. Cellulose is the natural stimulant to peristalsis 

 and activity of the canal. Cattle digest cellulose, and with 

 them it takes the place of starch. 



450. Vegetables. Root vegetables and tubers, such as 

 potatoes, sweet potatoes, and turnips, contain a small per- 

 centage of starch. But vegetables in general consist almost 

 entirely of water and woody fiber (cellulose). This is 

 especially true of green vegetables, or those which consist 

 of the leafy part of the plant. But green vegetables con- 

 tain nucleo-albumin, or iron-bearing albumin, which is of 

 great value to the blood and tissues. This form of albu- 

 min is easily destroyed in the intestine before it reaches 

 the blood, if fermentation takes place. As some leafy 

 vegetables are more likely to ferment if cooked, there is an 

 advantage in eating them raw. Iron and valuable mineral 

 salts are thus obtained. 



