374 DETECTION OF ADULTERATIONS 



spinosa and avium, Rosa canina, Fragaria vesca, Spiraea ulmaria, 

 Wistaria Sinensis. 



It will be seen that in most of these cases the fact of adul- 

 teration would be easily detected by the skilled microscopist, 

 but the source of adulteration could not be told without a pre- 

 liminary knowledge of the histology of the adulterant, and a 

 knowledge more intimate than could be obtained from pictures 

 and descriptions. It is clearly necessary for the investigator 

 to get a first-hand acquaintance with the possible adulterants. 



Estimating the Percentage of Adulteration. In some 

 instances it is possible to make a very close approximation of 

 the percentage of adulteration. Having determined the fact 

 and the source of adulteration, make preparation of different 

 and definite percentages of adulteration and compare them 

 with the sample under investigation for the relative frequen- 

 cies of some of the characteristic elements of the adulterant, 

 such as starch-grains, bast fibers, stone cells, hairs, etc. If 

 these elements are few the total number in the field of view may 

 be counted; but if their frequency makes this impossible the 

 count may be made in a definite portion of the eyepiece mi- 

 crometer. It is very important in doing this that the material 

 in all cases be evenly distributed under the coverglass, and that 

 a medium power objective be used, in fact as low a power as 

 will serve in identifying the different elements, in order that 

 the reliability of the results may be increased by- a comparison 

 of the larger areas which the lower powers embrace. An equal 

 distribution of the material under the coverglass can be ap- 

 proximated by giving the coverglass a gyrating motion under 

 gentle pressure of the forefinger covered with a clean cloth. 



