QUANTITATIVE MICROSCOPIC DETERMINATIONS 155 



variations in plants, more especially in the perennials. For example, 

 how does the bast, sclerenchyma and bark parenchyma in the bark of 

 the white oak vary from year to year, not only in the trunk of the tree 

 but also in the branches? Such a study would be of great value in 

 the practical application of the method in the examination of cinnamon 

 barks, sassafras bark, wild cherry bark, cascara bark and barks in 

 general. What is the annual increase in fibrous tissue in belladonna 

 roots? What is the relative amount of fibrous tissues in the wild 

 growing and in the cultivated chicory? What is the relative amount 

 of fibrous tissues in trimmed licorice roots and in the licorice trimmings? 

 What is the exact quantitative relationship of like tissues in the inner 

 and outer barks of the same species of trees? Since such data are not 

 available, they must be carefully ascertained for each individual case 

 or problem and the figures obtained carefully recorded. 



At best any quantitative microanalytical methods which may be 

 worked out will give approximate results only; however, these approxi- 

 mate results are sufficiently accurate for all practical purposes. The 

 chief factors in the variation of results are dependent upon the fact 

 that the tissue elements and cell constituents vary (in different vege- 

 table substances of the same kind gathered at the same time) in pro- 

 portion to the size of the plant part or plant organ. This difference 

 amounts to but very little in average commercial articles of the same 

 kind and may in fact be wholly ignored. The chief reason why the 

 microanalytical methods should be developed is because this is fre- 

 quently the only method which will give the information desired, 

 the chemical methods being wholly inapplicable. 



The following general method is given with the hope that it will 

 serve as a basis for a further development of this most important addi- 

 tion to the analytical methods employed in food and drug laboratories. 



1. Selecting the Sample. Secure an average commercial sample of 

 the crude drug or spice, free from impurities. Great care must be 

 observed in selecting and preparing an average sample. It should be a 

 true average sample of the commercial article of recognized standard 

 quality or grade, as defined by the Department of Agriculture, Bureau 

 of Chemistry, or in case the article is not defined or described by the 

 Bureau of Chemistry, it must be of the quality and grade generally 

 recognized in commerce, or as described or defined in recognizedly 

 authoritative works of reference. Foreign inclusions, as vegetable 

 tissues, dirt, clay, sand, pebbles, etc., must be removed by any suit- 

 able method, provided that none of the substance of the article itself 

 is thereby removed or destroyed or rendered unrecognizable. Enough 

 of the material must be taken to assure an average sample for ana- 

 lytical purposes. 



