STARCHES. 



77 



is not normally present, but is the product of a diastatic 

 ferment of some type, and that the starch grain is made 

 up of granulose,* the lamella ted appearance being due to 

 alternating variations in the watery content of the granu- 

 lose. This view of Nageli's has been taught for years, 

 but there seem to be objections to it. 



In the practical identification of many vegetable 

 products starch 'grains are the most important structural 

 elements, and a key to the identification of the common 

 starches in daily use is of ser- 

 vice in the diagnosis of adult- 

 erations. 



When examining specimens 

 containing starch it is advised 

 to examine the specimen first 

 in water, then bring to the 

 edge of the cover-glass a drop 

 of strong alcohol. This pro- 

 duces a streaming of the fluids 

 imder the cover-glass, rolls the 

 specimens about somewhat, and 

 thus gives a view of all sides of 

 the starch grains. 



In certain drugs, such as 

 Curcuma, Jalap, etc., the heat used in the curing of 

 the specimen often modifies the shape of the starch 

 grains. 



Classification. — There are numerous classifications of 

 starch grains; the most important of these are to be 

 found in Wiesner, ** Mikroskopische Technologie," and in 

 Nageli, " Starkekomer. " The classification of Vogl is 

 here given for reference. 



A. Granules simple, bounded by rounded surfaces. 

 I. Hilum central, layers concentric. 



a. Mostly rounded or from the side, lens-shaped. 

 ♦ For the latest and best r6sum6 see Meyer, Die StarkekOmer. 



Fig. 8. — Starch Graixs op 

 Potato (Sachs). 



