158 POWDERED VEGETABLE DRUGS 



solution of cherry gum, solution of gum mastic, gelatin solution, India 

 gum solution, plain vaseline, etc. It is advised to stir the material 

 in a little water first, as stated above, for if the gum solution should be 

 added at once, considerable difficulty may be encountered in getting 

 minute particles, starch granules in particular, evenly distributed. 

 It is of course necessary to stir and mix the suspension thoroughly 

 each time a new mount is to be made. 



5. Making the Counts. The mounts must be made without a time 

 lapse in the entire procedure. Immediately after the thorough mixing, 

 take up from 0.5 cc. to 1.00 cc. of the material by means of a graduated 

 straight cylinder pipette, having a free outflow (1 cc. or 2 cc. pipettes 

 graduated into tenths), reject 0.1 to 0.2 cc. and then deliver just 

 0.2 cc. upon the counting chamber or counting slide and at once mix 

 and spread this out between the two slips on the slide (use a platinum 

 loop or needle, or any blunt needle, or a very thin glass rod), and cover 

 with the special rectangular cover glass, by placing the proximal end 

 of the cover at the distal ends of the two slips, pushing it forward upon 

 the two slips, lying flat upon them. If the exact amount indicated 

 (namely, 0.2 cc.) has been properly spread and the cover glass care- 

 fully placed, the entire space between the two slips and the cover glass 

 will be occupied by the material without any excess .or overflow. The 

 mount should be set aside on a leveling table for a few minutes, other- 

 wise starch granules may become unevenly deposited by the force of 

 gravity. 



If the powders to be examined are very fine, as starches and some 

 meals, face powders, dusting powders, etc., the counts may be made 

 by means of the hemacytometer, instead of the above special counting 

 chamber. A number 80 powder does not permit the use of the hema- 

 cytometer for counting. It is perhaps self-evident that actual numer- 

 ical determinations per cc. or per gram may be made by means of the 

 method just outlined, since definite quantities and definite counting 

 areas are used. 



The following is the manner in which the individual field counts are 

 to be made. In the case of rather coarse particles, such as the larger 

 bast cells, groups of sclerenchymatous tissue cells, fragments of fibrous 

 tissue, fragments of vascular tissue, etc., for which the low power is 

 usually employed, count all of the recognizable structures which lie 

 within the circular area of the field of view, including all of the counting 

 groups lying across the margin of the field, provided, the groups or the 

 cells extend far enough into the field of view to be distinctly recognizable. 

 Next shift the mount so that the new field of view does not reveal any 

 of the counting elements of the preceding field. Unless this rule is 

 closely observed there is likelihood of counting one cell group twice. 



