114 STARCH' STRUCTURE. [BOOK i. 



brane, vegetable jelly, and perhaps also into gum. The 

 chemical composition of starch is now placed beyond doubt, 

 by the distinguished chemists Berzelius and Liebig, and is 

 given thus 



C H O 



12 20 10 



The following is a faithful account of my own experiments : 



A. Nature of Potato Starch. Potato starch, as usually pur- 

 chased, forms rather a coarse, shining white powder, mixed 

 with larger particles. It is easily rubbed fine between the 

 fingers, and it feels hard and gritty to the teeth. When 

 moistened, it forms bulky masses and remains so, without 

 falling to pieces when dry. But if starch is well washed at 

 long intervals with cold water, alcohol, and ether, it becomes 

 an extremely fine glittering powder, which will not hold 

 together if first moistened and then dried. Some time is 

 required to get the starch perfectly clean, and the cleansing 

 material for a long time shows signs of the presence of an 

 albuminous and fatty matter. 



This accounts for the conflicting opinions that have existed 

 regarding the composition of starch ; observers did not experi- 

 ment upon clean starch, but upon various sorts of impure 

 materials. Payen and Persoz first thought of thoroughly 

 cleansing starch before use, and the result of their experi- 

 ments was, that starch is a perfectly uniform vegetable 

 product. 



Under a microscope, magnifying 100 times, the single 

 particles of starch may be seen as small, fixed, egg-shaped 

 granules. Exceptions to this form are proportionally very 

 rare. On the pointed end of the most perfect and distinct 

 of those granules, fresh from the potato, a small black spot, 

 Fritscke's kernel (kern), may be seen. Very rarely, and only 

 with a much higher magnifying power, can this spot be viewed 

 in the potato, filled with a substance so thin that it is with 

 difficulty seen to be a hole in the solid mass. This may, 

 however, be seen much more distinctly in starch taken from 

 bulbs of some Lily worts. 



Around this so-called kernel, a number of lines are drawn, 



