METHODS OP EXAMINATION. 



27 



Abbe's Condenser. The second necessary adjunct is a com- 

 bination of lenses placed underneath the stage, for bringing 

 wide rays of light directly under 

 the object. It serves to intensify FIG. 7. 



the colored pictures by absorbing 

 or hiding the unstained structure. 



This is very useful in searching 

 a specimen for bacteria, since it 

 clears the field of everything that 

 is not stained. It is called Abbe's 



Condenser. Together with it is Abbe's Condenser. 



usually found an instrument for 



shutting off part of the light a blender or diaphragm. When 

 the bacteria have been found, and their relation to the structure 

 is to be studied, the " Abbe* " is generally shut out by the iris 

 blender, and the structure comes more plainly into view. A 

 white light (daylight or a Welsbach burner) is best for bacterial 

 study : use the plane mirror for daylight and the concave 

 mirror for artificial light. 



FIG. 8. 



Iris Blender. 



For all stained Bacteria the oil immersion lens and Abbe con- 

 denser, without the use of blender. For unstained specimens, 

 oil immersion and the narrowed blender. 



When examining with low power objective, use a strong 

 ocular. When using high power objective use weak ocular. A 

 nose-piece will be found very useful, since it is sometimes neces- 



