712 SCIENTIFIC AND APPLIED PHARMACOGNOSY 







starch grains, but it is very useful in the study of mechanical tissues, 

 hairs and calcium oxalate. 



After having determined the presence of starch, a separate 

 mount of the powder in water is made and the size and markings of 

 the grains noted. 



For the examination of more or less lignified cells, mounts are 

 made, either in phloroglucin or aniline sulphate solution; in some 

 cases it is advantageous to apply these solutions after the specimen 

 has been previously treated with chloral. Sometimes it is desirable 

 to study the mechanical cells more closely, and Schulze's macerating 

 fluid may be used for isolating them. 



Examination. Before making a microscopical examination of 

 coarsely comminuted or powdered drugs or foods it is desirable 

 to mix a small quantity of the material with a little water contained 

 in a watch crystal or small beaker and note such features as the fol- 

 lowing: (1) If the particles sink or float. In all genuine coffee, for 

 instance, the particles rise to the surface, whereas in the substitutes 

 and adulterants they sink. (2) If the particles disintegrate. All 

 artificial products, as coffee and nutmeg, when made from exhausted 

 powders or spurious substances, slowly disintegrate, leaving a fine 

 sediment. (3) The color of the solution. A chelidonium powder, 

 for instance, gives a golden-yellow solution, as also do many drugs 

 containing berberine and allied principles. (4) Behavior of the solu- 

 tion and particles toward alkalies or dilute hydrochloric acid. Drugs 

 containing oxymethyl-anthraquinone derivatives, as senna, rhu- 

 barb, aloes, frangula and cascara sagrada, are colored a deep red with 

 alkalies. The particles of ruellia give a distinct effervescence with 

 hydrochloric acid particularly if the mixture is slightly heated. The 

 presence or absence of starch may be determined by heating the 

 mixture, to which has been added a few drops of dilute hydrochloric 

 acid, filtering, and adding iodine to the filtrate when cool. (5) 

 The odor of the mixture, particularly on warming, is of considerable 

 value, as in the detection of belladonna in inula or of conium in anise. 

 The odor is also of value in recognizing the specimen, as very many 

 drugs have a characteristic odor. The odor of a specimen is some- 

 times, however, misleading, as a number of substances not at all 

 related may have a similar odor. The odor of elm bark, for instance, 

 is possessed by other substances, as fenugreek and wheat middlings, 

 particularly if these substances are kept in closed vessels. 



The fixed oil, which occurs in considerable quantity in many 

 seeds, interferes with their microscopical examination, and it is 

 necessary to remove this before making mounts of the material. 



