NON-NITROGENIZED ALIMENTARY PRINCIPLES. 181 



the sweetest, and the most agreeable. Beet-root sugar, so extensively used in France, is 

 perhaps as agreeable, but is not so sweet. 



Much of the sugar used in the nutrition of the organism is formed in the body from 

 the digestion of starch. This transformation of starch may be effected artificially. The 

 sugar thus formed is called glucose and is identical in composition with grape-sugar. 

 Except in the milk during lactation, this is the only form in which sugar exists in the 

 organism, all the sugar of the food being converted into glucose before it is taken into 

 the blood. 



Starch. A non-nitrogenized principle, closely resembling sugar in its ultimate com- 

 position (Ci 2 Hio Oio), is contained in abundance in a great number of vegetables. It is 

 found particularly in the cereals (wheat, rye, corn, barley, rice, and oats), in the potato, 

 chestnuts, and in the grains of leguminous plants (beans, peas, lentils, and kidney-beans), in 

 the tuberous roots of the yam, tapioca, and sweet-potato, in the roots of the Maranta 

 arundinacea* in the sago-plant, and in the bulbs of orchis. In the cereals, after desicca- 

 tion, the proportion of starch is, in general terms, between sixty and seventy parts per 

 hundred. It is most abundant in rice, which contains, after desiccation, 88'65 parts per 

 100. 



Starch may be separated from many plants by simple washing, but in others, in which 

 it exists in connection with a considerable proportion of gluten, a more elaborate process 

 is employed in commerce. The different varieties of manufactured starch, such as corn- 

 starch, potato-starch, arrow-root, tapioca, and sago, differ only in the presence of a 

 minute quantity of odorous and flavoring principles. 



When extracted in a pure state, starch is in the form of granules, varying in size from 

 nmnr to iro f an inch, and presenting, in most varieties, certain peculiarities of form. 

 The granule is frequently marked by a 

 little conical excavation called the hilum, 

 and the starch-substance is arranged in the 

 form of concentric laminae, the outlines 

 of which are frequently quite distinct. 

 "When starch is rubbed between the fingers, 

 these little hard bodies give it rather a 

 gritty feel and produce a crackling sound. 

 The different varieties of starch may be 

 recognized microscopically by the peculiar 

 appearance of the granules. 



The presence of even a minute quan- 

 tity of starch in any mixture which is not 

 alkaline may be readily determined by 

 the addition of iodine, which unites with 

 the starch, producing an intense-blue color. 

 The color may be destroyed by the addi- 

 tion of an alkali or by the application of F IG 44. Arrow-root starch-granules ; magnified 370 



heat. It may be restored, however, by 



the addition of an acid or, in the latter 



instance, it returns when the mixture is allowed to cool, if the temperature have not 



been carried to 212 Fahr. 



Starch is insoluble in water, but, when boiled with several times its volume of water, 

 the granules swell up, become transparent, and finally fuse together, mingling with the 

 water and giving it a mucilaginous consistence. The mixture on cooling forms a jelly- 

 like mass of greater or less consistence. This change in starch is called hydration and 

 is interesting as one of the transformations which takes place in the process of digestion, 



1 The creeping roots from which the substance known as arrow-root is manufactured. 



