.MICROSCOPICAL EXAMINATION OF POWDERED VEGETABLE DRUGS 71 



7. The required glassware and adjunct apparatus. 



8. The required reagents. 



9. Equipment for making moisture determinations. 

 10. Equipment for making ash determinations. 



The laboratory in which the work is done must be roomy, well- 

 lighted, provided with the necessary shelves, apparatus and supply 

 cases, reference books, etc. The analyst must see to it that the 

 necessary things are provided. A skillful worker should have the tools 

 of his choice. 



It is impracticable to enter into a full discussion of the technique 

 and methods to be employed by the micro-analyst. The following 

 suggestions will serve as a guide to methods of procedure. 



For microscopic examination a pinch of the powder is mounted in 

 some clearing fluid. Heat may be employed to remove air bubbles 

 and to increase the translucency. The student is at first greatly 

 confused by the optical picture which presents itself. Cell-fragments 

 and cell-contents are variously intermingled with various cell-groups, 

 but this confusion vanishes with experience and with the knowledge 

 of the histologic structure of plants. With the exception of very fine 

 meals, it will be found that cells occur in groups, the number of cells 

 in each group depending upon the fineness of the powder and the size 

 of the cells. Bast cells, trichomes, tracheids, wood cells, ducts and 

 other elongated elements appear in longitudinal view. Tabular 

 elements, as epidermal cells, appear in surface view. The more deli- 

 cate elements, as meristem cells, leaf parenchyma, pith cells, ordinary 

 isodiametric parenchyma, are usually pretty well broken. Scleren- 

 chyma cells are rarely broken and belong to the strikingly character- 

 istic elements noticeable in powders; the same may be said of the short 

 thick bast cells found in cinchona, cinnamon and some other drugs. 

 Hair cells, epidermal cells and pollen grains are quite diagnostic. 

 Glandular structures are of little significance in the examination of 

 powders, as they are usual'y too much broken. Cell-contents are 

 very important, especially the starches and the crystals of calcium 

 oxalate. Starch granules usually appear entire, likewise the crystals 

 of calcium oxalate, excepitng the large crystals, as they occur in scilla, 

 rhubarb, soap bark, orris root and in a few other drugs, which are 

 more or less broken in the powdering. 



It is rarely desirable or necessary to use many micro-chemical 



reagents in the study of vegetable powders. An intelligent use of a 



suitable clearing fluid, 1 a solution of chloriodide of zinc and a J^o 



normal iodine solution is about all that will be required. To hasten 



1 A mixture Jof equal parts of glycerin and water will be found most useful. 



