8i2 BOTANY AND PHARMACOGNOSY. 



Dried Material. Most of the vegetable drugs and some of 

 the vegetable foods occur in commerce in a more or less dried 

 condition, and in order to study them microscopically it is usually 

 necessary to give them some preliminary treatment. With the 

 majority of drugs, soaking in hot or cold water for from a few 

 minutes to a few hours will render them sufficiently pliable or soft 

 for sectioning. After this the material is hardened by placing it 

 in alcohol (60 to 70 per cent.) for a few hours or over night. 

 It may then be sectioned and treated with special reagents or 

 stains as desired. Very hard material, as the shells of nuts and 

 seeds, may be softened by soaking in solutions of potassium 

 hydrate. 



Some Practical Suggestions. The following are some of 

 the rules which should be borne in mind by the student when 

 using the microscope- in the examination of vegetable drug 

 material : 



1. Always mount the sections (including powdered material) 

 in water or other suitable reagent prior to examination, never 

 attempting to examine dry material except in special cases. 



2. Use sufficient of the mounting medium or reagent to cover 

 the specimen, but avoid an excess or more than will be held under 

 the cover-glass. 



3. Always endeavor to have the object properly illuminated 

 by making use of the concave mirror. 



4. Always be pa/ticular about having the eye-piece and objec- 

 tives clean. 



5. In examining a preparation, always use the low-power 

 objective first. _ 



6. The edge of a section is always the thinnest, and this part 

 being the best for study, should be brought to the center of .the 

 field. 



7. When the object is properly centered, raise the objective, A 

 swing it to one side, bring the high-power objective into its place, 



and cautiouslv lower it until it is brousfht to about the distance 

 of a millimeter from the cover-glass. Then holding the slide 

 with the left hand, the proper focus of the object is obtained by 

 making use first of the coarse adjustment and then of the fin,e 

 adjustment, the right hand being used for this purpose. In 



