The Lycopodium Method of Quantitative Microscopij. 177 



lycopodium spores present in 20 fields evenly distributed along 

 the same diameter was 100, giving an average of 5 spores per field 

 of view; hence in the whole diameter (equal to 45*8 fields 

 of view) there were 5 x 45*8 = 229 spores. There were there- 

 fore 71 pollen grains for every 229 lycopodium spores, and hence 

 71 X 94,000 -4- 229 = 29,100 pollen grains for every milligramme 

 of lycopodium ( = 94,000 spores). Hence for * 05 milligramme of 

 lycopodium there were 29,100 -4- 20 = 1450 pollen grains, and 

 since 0*05 milligramme of lycopodium was mixed with every 

 milligramme of insect flowers there were 1450 pollen grains per 

 milligramme of insect powder, which was therefore a perfectly 

 satisfactory example from this point of view. 



Conclusion. 



Other more difficult problems upon which a certain amount of 

 preliminary research has already been done are such as the deter- 

 mination of the percentage of wheat flour in mixtures of wheat 

 and barley, and of the percentage of foreign stone cells in powders 

 like pepper and gentian. Almost every problem presents its own 

 special difficulties which may involve an inquiry into the range of 

 variation found in different varieties of the same material, and a 

 much more close scrutiny of details than has been necessary where 

 only qualitative results were desired. For this reason progress 

 must be slow, but the fundamental principle of the lycopodium 

 method is applicable in all cases, and an ultimate solution of the 

 difficulties is brought within the reach of microscopists. 



Eeferences. 



1. Cleaver, E. L. — Admixture of Oatmeal with Barley-Meal. Analyst 



(1877) 1, p. 189. 



2. Bell, James — The Analysis and Adulteration of Foods (1883) pt. 2, 



p. 151. 



3. Allen, A. H. — Commercial Organic Analysis, 4th edit. i. (1909) p. 417. 



4. Clark, Frederick C. — The Microscopical Examination, Physical Test- 



ing, and Chemical Analysis of Paper (New York, 1917). 



5. SiNDALL, E. W.— Paper Technology (1906) p. 149. 



6. Meyer, Arthur — Grundlagen und Methoden fur die mikroskopische 



Untersuchung von Pflanzenpulvern (1901) pp. 125-37. 



7. Der Artikel " Flores Koso " des Arzneibuches und eine neue 



Methode der quantitativen mikroskopischen Analyse. Archiv der 

 Pharmazie (1908) 246, pp. 523-40. 



8. Linde, 0. — Zur Untersuchung des Kosobliitenpulvers. Apotheker- 



Zeitung (1911) 26, p. 136. 



9. Hartwich, C, & WicHMANN, A. — Einige Beobachtungen an Starke- 



kornen und iiber die Zahlkammer, ein Hilfsmittel zur quantitativen 

 Ermittelung von Verfiilschungen vegetabilischer P'jlver. Archiv der 

 Pharmazie (1912) 250, p. 452. 



N 



