42 MAHUAL OF CATTLE-FEEDIKa. 



growtli, and vary in size and appearance according to tlie 

 species of plant wliicli produces tliem, so that starcli from 

 different sources can be readily distinguished. 



They are composed of two substances — a skeleton of a 

 mateiial resembling cellulose and called BtaTch-celUilosey and 

 a more soluble substance called granuloses which constitutes 

 by far the larger part of the grains. A characteristic 

 property of starch is that, when brought in contact with a 

 minute quantity of iodine in solution, it assumes a beauti- 

 ful blue color. This property seems to reside in the granu- 

 lose, since, if this be removed by solvents, the residue 

 gives no longer a blue but a yellow color wdth iodine, like 

 ordinary cellulose. 



Starch is insoluble in cold water so long as the grains 

 remain whole. If they are crushed and ground very fine 

 with water, a minute quantity is dissolved. 



"Wlien heated with water nearly to boiling, the grains swell 

 and burst, absorbing water and forming a jelly-like mass, 

 but very little starch is really dissolved by this treatment. 



Starch, like cellulose, may be converted into dextrine and 

 grape-sugar by boiling with acids or alkalies, but much 

 more readily. The same transformation may be effected 

 by dry heat, and by the action of diastase,"^ the ferment 

 of malt, as in the preparation of beer and spirits. 



It is also rapidly dissolved and converted into sugar by 

 the action of the saliva of the mouth and by the pancre- 

 atic juice, and is, indeed, one of the most important of 

 the non-nitrogenous nutrients, owing to its abundance and 

 the comparative ease and completeness with which it is 

 digested- 



* Diastase produces a peculiar kmd of sugar called maltose, instead 

 of grape sugar. 



