CHAPTER XI 

 QUANTITATIVE MICROSCOPIC DETERMINATIONS 



It is frequently desirable to make quantitative determinations by 

 means of the compound microscope, and a number of tentative 

 methods for doing such work have been proposed from time to time 

 by various authors. Thus Meyer (Die Grundlagen und die Methoden 

 fur die Mikroscopische Untersuchung von Pflanzenpulvern, 1901) 

 proposed some methods which have served as the basis for others to 

 build upon. The following suggestions will be found comparatively 

 simple and will serve many practical purposes. 



The quantitative microscopical methods are based upon the prin- 

 ciple that certain cell forms and cell contents generally occur in fairly 

 uniform amounts or quantities in plant parts at certain periods of 

 their development. Thus, green apples bear starch granules numeric- 

 ally inversely proportional to the stage in the development of the 

 apple; that is, the green apple contains starch whereas the ripe apple 

 is free from starch. The quality of gum tragacanth is inversely pro- 

 portional to the number of starch granules present. A good quality 

 of belladonna root contains a fairly definite amount of starch granules, 

 whereas belladonna root gathered too early in the season contains 

 less starch. Again, the problem may be to determine the relative 

 amounts of wheat flour and of buckwheat flour in a pancake mixture ; 

 or the amount of cereal added to sausage meat, or the amount of 

 tragacanth or starch filler in ice cream. Or, the problem may be to 

 determine the approximate degree of decomposition in soda fountain 

 fruits or syrups, or in medicinal syrups, etc. The following selected 

 examples and problems will serve to make clear the possibilities in 

 this comparatively new field of microanalysis. 



The equipment for this work, in addition to what has already been 

 given, is as follows. 



APPARATUS AND REAGENTS 



1. 25 cc. graduated cylinders, open. Closed cylinders may be used. 



2. Straight graduated pipettes, 1 cc. capacity, with free outflow. 



3. Hemacytometer with Turck ruling, or the Levy counting cham- 

 ber with Turck ruling. 



4. Stage micrometer scale. 



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