14 PHARMACEUTICAL BOTANY 



immersion oil (slightly evaporated cedar oil) should be placed on the 

 cover glass directly above the object and the body tube should be 

 run down with the coarse adjustment until the front lens of the 

 immersion objective enters the drop and comes almost into contact 

 with the cover glass. This should be done while watching the objec- 

 tive. Then look through the ocular and draw the objective up with 

 the fine adjustment until the object comes into focus. 



RULES FOR THE CARE OF THE MICROSCOPE 



1. In carrying the microscope to or from your table, grasp it 

 firmly by the pillar and hold in an erect position, so that the ocular 

 which is fitted loosely into the draw tube may not fall out and its 

 lenses become damaged. 



2. Never allow the objective to touch the cover glass or the liquid 

 in which the object is mounted. 



3. Never touch the objective or ocular lenses with fingers or cloths. 



4. Never change from lower to higher power objective without 

 first ascertaining that the body tube has been raised sufficiently to 

 allow the high power objective to be slipped into place without 

 injury to the objective or mounts. 



5. Never clean the microscope lenses or stand with cloths that 

 have been used for removing surplus of alkali, acid or other reagent 

 from slides. 



6. Note whether the front lens of the objective is clean before 

 attempting to use it. If soiled, breathe on the lens and gently wipe 

 with an old, clean, soft handkerchief or lens paper. If the lens be 

 soiled with balsam or some other sticky substance, moisten the 

 handkerchief or lens paper with a drop of xylol, taking care to wipe 

 it perfectly dry as soon as possible. 



7. Do not let the objective remain long near corrosive liquids, 

 such as strong solutions of iodine, corrosive sublimate, or mineral 

 acids. Never examine objects lying in such fluids without putting 

 on a cover glass. 



8. Never lift the slide from the stage, but, after raising the objec- 

 tive, slide it off the stage without upward movement. 



9. Never allow the stand (microscope without lenses) to be wetted 

 with such substances as alcohol, soap, etc., which dissolve lacquer. 



10. Keep the microscope covered when not in use. 



