MICROSCOPICAL DIAGNOSIS. 



more transparent. Yet generally they can be identified when sub- 

 jected to either dry or moist heat, if the moist heat be not raised to 

 the boiling point. The large grains of wheat starch, in their normal 

 state, are very uniform in size for the same variety, but -the starch- 

 grains of the different varieties differ considerably in size. The 

 average diameter of the grain in the eight varieties examined is - T 

 of an inch.f Barley and rye are closely related to wheat. All of 

 these are used extensively for adulterations. 



Barley Starch is composed of large and small grains. The large 

 grains are smaller than those of wheat ; being about r ^ Tr of an inch 



r . 32. Bean Starch, A'j 



in diameter. There is less difference between the long and the short 

 diameters than in wheat starch, so that when the grains are rolled 

 over they present less of a lens-shape, being rounder. Rings and a 

 star-shaped nucleus are quite frequently apparent. The small grains 

 are more angular, frequently having a nucleus, and average ^ S ', MI <>t 

 an inch in diameter. No cross is seen when viewed with polari/ed 

 light. 



Rye Starch grains are larger than those of wheat, very seldom 

 do they show any rings, and when present they are eccentric ; occa- 



tThese measurements were made by Mrs. Stowell. In each case 20 grains, as 

 nearly typical as possible, we r e selected, and accurately measured; the average was then taken, 

 with the following results: The largest grains of Tread well wheat measured 1-861 ,of an inch 

 in diameter; Deihl. 1-816 ; Wicks. 1-881 ; Egyptian, 1-904 ; Russian, 1-1174 ; Clawson, 1-1256; 

 Schaffer, 1-1000 ; Vienna flour, 1-861. There is also considerable difference in the size of the 

 small grains. Schaffer small grains measure 1-4700 of an inch in diameter ; Treadwell, 1-6102 ; 

 Vienna flour, 1-5166 ; Russian, 1-400 ; Egyptian, i 6coo. 



