664 STARCH 



When mixed with water above 120 .Fahr., the starch grains 

 burst ; the granulose, escaping, occupies twenty to thirty 

 times its previous volume, and forms the viscid gelatinous 

 mucilage used by the laundress. A solution of starch when 

 cold gives the characteristic blue compound with solution 

 of iodine. Starch, when boiled with diluted sulphuric or 

 nitric acid, or heated, is converted into the isomeric but 

 more soluble dextrin or British gum, one variety of which 

 is coloured red by iodine. With further action of a weak 

 acid and heat, dextrin takes up water and is converted into 

 maltose (C^H^On.HaO), and eventually into dextrose 

 (C 6 H 12 6 ). 



When starch foods are eaten the salivary and intestinal 

 ferments or enzymes gradually resolve the granules, and 

 quickly convert the starch through several forms of dextrin 

 into maltose, and eventually into dextrose. These changes 

 are also readily produced by mixing starch paste with 

 crushed malt, the diastase of which develops the fermenta- 

 tive changes. Animal starch, or glycogen (C 6 H 10 5 )x., 

 present in the liver, in blood, and in muscle, exhibits most 

 of the characters of vegetable starch. 



ACTIONS AND USES. Starch foods are rapidly digested, 

 especially when cooking or fermentation has cracked the 

 starch cells, or when they have been thoroughly insalivated. 

 Like other such proximate principles, pure starch cannot, 

 however, alone support life for any lengthened period. A 

 properly balanced dietary for horses or cattle should contain 

 one part of proteids and five to eight parts of starch or 

 other carbo-hydrates. Active exertion, as in the case of 

 hard-worked horses, or abnormal secretion, as of heavily- 

 milking cows, causes great expenditure of albuminoids, 

 which must be replaced by the food. Growing animals, in 

 order to build up their tissues, require relatively larger 

 supplies of albuminoids than suffice for adults. The starches 

 mostly converted into sugar are consumed in the body 

 more quickly and fully than fats. During their oxidation 

 they are the great source of animal heat, especially in herbi- 

 vora. They prevent wasteful consumption of the more 

 costly albuminoids and fats. Under favourable condi- 

 tions, carbo-hydrates, in excess, are also directly concerned 



