500 POWDERED DRUGS 



middlings in ginger has been a common practice. Sometimes inorganic 

 substances such as talc, chalk, clay, sand, etc., are employed. One of the 

 most difficult means of adulteration to detect is the use of exhausted pow- 

 ders (the dregs left from drugs extracted by percolation). These are first 

 dried and repowdered and mixed in various proportions with the pure 

 article. Deteriorated drugs have been used in the same way. It goes 

 without saying that these latter forms of adulteration can not readily be 

 detected microscopically, but a microscopical examination in connection 

 with careful chemical tests is of the greatest value. 



A thorough knowledge of the histology of the plant part supposed to 

 constitute the powder is necessary. And for this purpose cross and longi- 

 tudinal sections, which may be prepared after soaking the dried drug 

 materials in water, may, in many cases, be used to great advantage. By 

 careful comparisons of sections and broken fragments, and the employ- 

 ment of proper reagents upon cell-products, identification is made positive. 

 For a full account of cell-products and reagents, see Part IV, Chapters 

 II and III. 



Mounting Powders for Examination. Powders for microscopical ex- 

 amination should be thoroughly mixed, so that the large and small particles 

 will be uniformly distributed throughout the entire specimen, as before 

 stated. In powders that have been standing for a considerable time the 

 larger particles will be separated from the finer, so that great difficulty 

 may be encountered in obtaining a typical mount from such a powder, 

 unless it has been thoroughly mixed. Only a small portion of powder 

 should be used in making a mount, the amount depending upon the size 

 of the cover-slip to be used. When the mount is ready for examination, 

 the particles should be spread out evenly and should not come in contact 

 one with another so that the large ones might obscure the smaller. 



Powders for examination may be mounted directly on the slide, using 

 the proper medium, or the powder may be mixed with the mounting me- 

 dium in a small test-tube, specimen tube, or homeopathic vial. If a small 

 portion of powder be transferred to a slide, a drop of the desired mounting 

 medium added, and the whole thoroughly mixed and covered with a cover- 

 slip, it will furnish a mount ready for examination. However, it is fre- 

 quently desirable or even necessary to use some clearing agent in order to 

 render dark colored or opaque powders transparent. In such cases the 

 powder should be thoroughly mixed with the reagent and left standing 

 for twelve hours or more, when a portion may be taken up with a pipette 

 and a drop of the mixture transferred to a slide. 



Clearing Agents and Mounting Media. For making temporary 

 mounts of powders water is the best general medium, and should be used 

 whenever a clearing agent is not required. In this medium delicate mark- 

 ings are clearly brought out, and it is especially recommended for the ex- 

 amination of starches. Frequently specimens are filled with air, which 



