MICROSCOPICAL EXAMINATION OF POWDERED VEGETABLE DRUGS 77 



Special tests: Pebbles picked out by hand, about 4 per cent. Senna 



seeds, pod fragments and stems present. 

 Microscopical findings: The histological characters of African senna. 



Stem tissue excessive. Sand and dirt excessive. Senna seeds 



and pods present in considerable quantity. 

 Conclusions: Adulterated with sand, pebbles, senna seeds, senna 



pods and stems, 25 per cent. Misbranded because labeled U. S. 



P., whereas it is below the U. S. P. standard. Corresponds with 



what is known in commerce as Senna siftings or Senna refuse. 



Richard Roe, Analyst. 



The skilled micro-analyst has little difficulty in determining the 

 purity and comparative quality of the simple spices, as pepper, all- 

 spice, cloves, cinnamon and ginger. However, matters are not so 

 easy or simple when it comes to the examination of powdered vegetable 

 drugs, compound vegetable powders and vegetable products of un- 

 known composition. A thorough knowledge of and wide familiarity 

 with cell-forms, tissue elements and formed cell-contents is an absolute 

 essential in order that accurately reliable and conclusive results may 

 be obtained and serious confusion may be avoided. Marked differ- 

 ences in the reports of findings by micro-analysts are in part due to the 

 personal equation, in part due to variations in methods and also to 

 differences in judgment in estimating the quantity of tissue elements 

 present and in part due to a lack of extensive and intensive experience. 



The true worth of the work of the micro-analyst has thus far not 

 been properly valued. The doubt in the minds of the critics is due, 

 very largely, to the unsatisfactory results traceable to the efforts of 

 those who are not sufficiently qualified. Even the most skillful 

 analysts admit numerous defects and shortcomings in methods and in 

 results. For example, the quantitative estimates based upon optical 

 judgment are approximate only, and with most workers there is a 

 very marked tendency to make these estimates volumetric rather than 

 gravimetric. This can in a measure be corrected by bringing into 

 play the judgment of the relative weights of the several substances 

 under comparison. For example, the amount of sand present in 

 powdered belladonna root may be volumetrically estimated at 20 

 per cent. In this case the acid insoluble ash residue may sho^ 35 to 

 40 per cent, of silica. An example like this also indicates why the 

 micro-analyst should make the sand and ash determinations. The 

 percentage estimates based upon microscopical examination may vary 

 within 25 to 50 per cent, when small amounts of admixtures are 

 considered. For example, the actual amount -of arrow-root starch 



