76 ELEMENTS OF /IPPLIED MICROSCOPY. 



bulk of the sample should be made up of the inner cell- 

 contents. If an excess of the outer layers be present, it 

 is evident that mustard-hulls have been added; and this 

 is one of the commonest adulterations to which this sub- 

 stance is subjected. Wheat- and rice-starch are also 

 found not uncommonly, and furnish conclusive evidence 

 of sophistication. Yellow aniline dyes are sometimes 

 used to give the proper color to such adulterated samples. 

 Turmeric, which is the ground rhizome of Curcuma 

 longa, is also well adapted for the adulteration of mus- 

 tard. It appears under the microscope in small amor- 

 phous, intensely yellow, pasty masses, which stain blue 

 with iodin, being made up largely of curcuma-starch. 



7. The Microscopic Structure of Pepper. — Pepper is 

 the pulverized seed of Piper nigrum, a shrub cultivated 

 mainly in the East Indian islands. The dried seed is 

 about 5 millimeters in diameter and is covered with a 

 brownish hull. If this hull is ground up with the grain, 

 we have the ordinary black pepper. White pepper is 

 made by macerating the fruit in water before drying, and 

 detaching the hulls by friction. 



In ground black pepper a number of tissues may be 

 made out, since the many-layered hulls are relatively 

 thick as compared with the more homogeneous central 

 portion. The latter forms the bulk of the preparation, 

 and is quite characteristic in appearance. It consists of 

 irregularly angular whitish masses, seen to be made up 

 of polygonal cells packed full of very minute starch- 

 grains (5 and 55, Fig. 31). With a high power these 

 grains themselves appear polygonal and closely aggre- 



