82 BACTERIOLOGY. 



chapter on micro-photography. The unit of measurement is one 

 thousandth of a millimetre or a micro-millimetre or micron, and is 

 expressed by the Greek letter /JL. 



CARE OF THE MICROSCOPE. 



After use the objectives, sub-stage condenser, and eye-piece 

 should be carefully wiped with soft linen, an old silk handkerchief, 

 or chamois leather, and the microscope covered with a bell-glass to 

 protect it from dust. If a lens comes into contact with Canada 

 balsam it must be very carefully wiped with a soft rag moistened 

 with alcohol, and then cleaned with a soft leather. Microscopes 

 should not be exposed to the fumes of sulphuretted hydrogen^ 

 chlorine, or volatile acids. 



