ON MICROSCOPICAL EXAMINATION. xxvii 



In using the microscope the following rules are to be 

 carefully observed : 



1. Examine every object with the low power first. Having 

 adjusted the eye-piece and the objective, turn the mirror so 

 as to reflect the light up the body of the microscope ; place 

 the object on the stage under the objective, and carefully 

 lower the body with a screwing motion till the objective is 

 about a quarter of an inch from the cover-glass ; then look 

 through the eye-piece, and gradually raise the body till the 

 object becomes distinctly visible. Focus accurately with the 

 fine adjustment screw. With the high power, begin with the 

 objective close to the cover-glass, and then proceed as before. 



2. Never examine an object with the high power unless 

 it is protected by a cover-glass. Take extreme care never to 

 let the objective touch the cover-glass, and never to touch 

 the face of the objective or allow any dirt to get on it. The 

 face of an objective cannot be cleaned without doing harm 

 to it. 



3. Keep both eyes open when looking through the micro- 

 scope. Also get into the habit of using either eye. 



4. When examining an object, keep one hand on the fine 

 adjustment, and keep screwing it up and down slightly. In 

 this way parts of the object at different depths are brought 

 into focus, and a much clearer idea of the object is obtained. 



5. With a high power, use a small diaphragm : the amount 

 of light will be somewhat diminished, but the clearness and 

 definition much increased. 



6. See that the body of the microscope slides smoothly in 

 its tube. If it does not, remove it, and clean it by rubbing 

 with a few drops of olive oil ; wipe off the oil before replacing 

 in the tube. Clean the inside of the tube in the same way. 



7. The object may appear indistinct from dirt in any of 

 the following places i.e. on the eye-piece, the objective, or 

 the cover-glass. If it be on the cover-glass, the dimness 

 varies when the slide is moved ; if on the eye-piece, it varies 

 when this is rotated ; if not on either of these, it must be on 

 or in the objective. 



The eye-piece and the lower surface of the objective may 



