QUANTITATIVE MICROSCOPIC DETERMINATIONS 163 



little value because this substance is present in small amounts and is 

 furthermore quite variable in amount in the different varieties of cocoa. 

 The endosperm cell count is impracticable because the cells are very 

 much broken up. The amount of vascular elements (represented by 

 spiral ducts) and of sclerenchyma cells is negligible in absolutely pure 

 (wholly freed from shells by hand) cocoa and chocolate. 



In the case of aconite root, belladonna root, colchicum corm, gin- 

 ger, and other plant structures rich in starch, a careful starch count 

 would indicate whether or not the article was gathered out of season 

 or before maturity. In the case of leaves and herbs which contain 

 distinctive trichomes, as senna, digitalis, artemisia, etc., these struc- 

 tures would serve as the basis for percentage determinations. In 

 other cases measurements (relative size of starches in Rio and Cartha- 

 gena ipecacs, relative lengths of trichomes in India and African senna) 

 must be resorted to in order to determine percentage admixtures. 



In many instances it may not be necessary or even desirable to 

 reduce the substance to uniform fineness. In a compound, as cattle, 

 chicken or condition powder, one or more of the components (as bran, 

 crude fiber, sulphur, charcoal, meals) may be separated in comparative 

 purity by means of the nest of sieves; the several coarse and compara- 

 tively pure components are weighed and their percentage values finally 

 computed. The finer components are mixed and reduced to the 

 desired fineness for making the microscopic counts as already ex- 

 plained, and the results added to those obtained by the sifting process. 

 The following will serve as an illustration of the method of procedure. 



A Condition Powder, using ten grams of a well mixed sample. 



Total weight of sample 10.0 grams 



Bran, on coarse mesh 2.3 grams 



Corn meal, on next finer mesh 3.6 grams 



Finer remainder, on No. 60 mesh 4.1 grams 



The finer remainder reduced to a No. 200 mesh powder and ex- 

 amined microscopically gave the following counts (one gram of the 

 powder suspended in 99 cc. of the gum solution). 



Corn starch 51,000,000 per gram 



Wheat starch 8,000,000 per gram 



Sulphur particles 13,000,000 per .gram 



Charcoal particles 32,000,000 per gram 



Wheat tissue elements 800,000 per gram 



In the above counts the corn starch count is to be interpreted in 

 terms of corn meal, as no corn starch was added as such. The wheat 

 starch count and crude fiber of wheat is to be interpreted as wheat 



