THE MICROSCOPE 



39 



The stage D serves as a table on which to place the object to 

 be examined. Immediately beneath the opening in the stage is 

 the Abbe condenser E, a system of lenses which serves to condense 

 the rays of light passing from the mirror F to the object in such a 

 way as to give the greatest luminosity possible. 



FIG. 12. Microscope. 



The iris diaphragm G is placed between the condenser and the 

 mirror and serves the same purpose as the iris of the eye in regulat- 

 ing the amount of light admitted. For unstained preparations, 

 when it is desired to bring out in relief the margins of the organisms 

 to be studied, a small aperture of the diaphragm is used in conjunc- 

 tion with the concave mirror. For stained preparations the 



