1892.] MICUOSCOriCAL JOUHNAL. 265 



by the aid of a small piece of bibulous paper, which, too, serves to 

 remove the excess of water protruding lieyond the edge of the 

 cover-slip. A few drops of alcohol dropped upon one of the 

 edges of the latter and drawn through the licpiid imder the cover- 

 slip by means of a piece of bibulous paper placed on the opposite 

 side very Irequently removes the most stuborn air bubble. 



Our slide is now ready for examination under the microscope. 

 As the water is very apt to evaporate before the examination is 

 completed, it is well to drop a drop of the same on the edge be- 

 tween the glass and the cover-slip during the course of the exam- 

 ination. Having adjusted the objective of the lowest power, say 

 forty diameters, in place, we set our microscope so that it is fac- 

 ing the source of light, and then adjust the mirror b}- looking 

 through the ocular at the field until we are convinced that the 

 e-ntire field is most completely illuminated. We now place our 

 slide upon the object-stand and slide the tube up and down until 

 we can see the section fairly accurately. The final focusing is 

 then done by means of the micrometer screw attached to the side 

 of the tube. With an objective that magnifies about forty diam- 

 eters we usually can see all of the section, provided the latter is 

 not broader than one-quarter of an inch, which it should not be, 

 to be of practical value. After having taken a general view of 

 the section, we turn to our book of plates and see if any of the 

 latter are similar, or very nearly so, to the same. In some cases 

 it is necessary to insert an objective of a higher power and ex- 

 amine certain parts more in detail, and then compare these again 

 with our plate. It may also be necessary, in some cases, where 

 thei^e are many varieties of the same species, as, for instance, the 

 cinchona barks, to make a longitudinal section in order to decide 

 upon the exact variety, as many of the latter are almost, if not 

 exactly, the same in cross-section. 



As a rule, we will not have to resort to staining, by staining 

 agents, in order to decide what drug we have in hand, but it is 

 sometime necessary, and always pretty and interesting, to add a 

 few drops of one of our staining agents to fully decide upon cer- 

 tain features of the drug section; for instance, which is cellulose 

 and which is woody fibre, or which is starch and which inuline 

 or crystals of inorganic salts. This is, however, only a refine- 

 ment and not necessary for the decision of what we are examin- 

 ing. The staining agents most generally used and most decided 

 in their action are the following: 



ANILINE SUI-PIIATE. 



Distilled water ....... lo ccm. 



Sulphuric acid ....... i drop. 



Aniline sulphate ....... o.i gm. 



PHI.OROGLUCINE. 



Five per cent, solution of phloroglucine in absolute alcohol 

 made acid by concentrated hydrochloric acid. 



