MICROSCOPY OF THE COMMON STARCHES. 6i 



until the seventeenth century that the potato was used as 

 a source of carbohydrate; and corn-starch is of course a 

 still more recent product. These three are by far the 

 most important of the starches. As might be inferred 

 from the scale of prices given above, corn-starch is used 

 for most purposes, the amount produced in the United 

 States in 1903 being probably in the neighborhood of 

 75,000 tons. Potato-starch ranks next with a produc- 

 tion of i6,coo tons in 1903, and the amount of wheat- 

 starch was perhaps 10,000 tons. 



The purposes for which this great supply is intended 

 may be grouped- roughly under four heads: starch is 

 used for a food material, for stiffening and sizing, as a 

 powder, or as a raw material for the manufacture of 

 other substances. Mixed with nitrogenous bodies, in 

 the form of flour, its supreme importance is of course as a 

 nutritive substance ; and even the purified product, in the 

 case of corn-starch, forms no insignificant contribution to 

 our dietary. The sago and tapioca flours are mainly 

 used for food, and the various arrowroots contain starches 

 recommended as particularly desirable for invalids. 



The principal commercial importance of refined starch, 

 however, comes from the fact that when in contact with 

 hot water its grains swell up and burst, forming a thick 

 adhesive paste. This may be best brought about by 

 mixing starch with cold water and slowly pouring the 

 thick milky fluid into boiling water which is meanwhile 

 agitated by constant stirring. The paste thus formed 

 imparts to textile materials a high degree of lustre and 

 that stiffness from which the name of starch (German, 



