VEGETABLE FOODS. 303 



and expanded during baking, forms cavities in it and causes 

 it to "rise" and make "light bread," which is not only 

 more pleasant to eat but more digescible than heavy. Other 

 cereals may contain a larger percentage of starch but none 

 have so much gluten as wheat; when bread is made from 

 them the cai bon dioxide gas escapes so readily from the less 

 tenacious dough that it does not expand the mass properly. 

 Corn contains in 1000 parts, 79 of proteids, 637 of starch, and 

 from 50 to 87 of fats; much more than any other kind of 

 grain. Rice is poor in proteids (56 parts in 1000) but very 

 rich in starch (823 parts in 1000). Peas and beans are rich 

 in proteids (from 220 to 260 parts in 1000), and contain about 

 half their weight of starch. Potatoes are a poor food. They 

 contain a great deal of water and cellulose, and only about 

 13 parts of proteids and 154 of starch in 1000. Other fresh 

 vegetables, as carrots, turnips and cabbages, are valuable 

 mainly for the salts they contain; their weight is mainly due 

 to water, and they contain but little starch, proteids, 

 or fats. Fruits, like most fresh vegetables, are mainly valu- 

 able for their saline constituents, the other foodstuffs in them 

 being only present in small proportion. Some form of 

 fresh vegetables is, however, a necessary article of diet; as 

 shown by the scurvy which used to prevail among sailors 

 before fresh vegetables or lime-juice were supplied to them. 

 The Cooking of Vegetables. This is of more importance 

 even than the cooking of flesh, since in most the main ali- 

 mentary principle is starch, and raw starch is difficult of 

 digestion. In plants starch is nearly always stored up in 

 the form of solid granules, which consist of alternating 

 layers of starch cellulose and starch yraniilose. The diges- 

 tive fluids turn the starch into sugars which are soluble 

 and can be absorbed from the alimentary canal, while starch 

 itself cannot. Now these fluids act very slowly and imper- 

 fectly on raw starch, and then only on the granulose; but 

 when boiled, the starch granules swell up, and are more 

 readily converted into the sugars, and the starch cellulose 

 is so altered that it too undergoes that change. When starch 

 is roasted it is turned into a substance known as soluble 

 .starch w r hich is readily dissolved in the alimentary canal. 



