346 THB MICROSCOPE. 



of an article very much more nutritious. This adulteration, 

 can be instantly detected by means of the microscope. 

 The cells which contain the starch- corpuscles are, in the 

 potato, very large, fig. 190 ; in the raw potato they are 

 adherent to each other, and form a reticulated structure, 

 in the meshes of which the well-defined starch- granules 

 are clearly seen ; in the boiled potato, however, the cells 

 separate readily from each other, each forming a distinct 

 article : the starch-corpuscles are less distinct and of an 

 altered form. 



Fig. 191. Adulterated Cocoa, sold under the name of Homoeopathic Cocca. 

 (After Hassall.) 



aaa, granules and cells of cocoa; bbb, granules of Canna-starch, or Tous-les- 

 mois; c, granules of Tapioca-starch. 



Adulteration with alum and "stuff." This adulteration 

 is practised with a twofold object : first to render flour of 

 a bad colour and inferior quality white and equal, in 

 appearance only, to flour of superior quality ; and secondly 

 to enable the flour to retain a larger proportion of water, 



