50 LABORATORY GUIDE IN BACTERIOLOGY 



14. After using the oil-immersion lens, wipe the oil 

 off with lens paper. If the oil sticks to the lens, wipe 

 it off with xylol, never with alcohol. At the same time 

 wipe the oil off the cover slip. 



15. The microscope should stand on a firm table, 

 to avoid being shaken. The table should be low enough 

 so as not to necessitate bending the body. 



16. Always keep both eyes open. This saves the 

 eyesight. Beginners find this a difficult rule to apply, 

 but with very little practice and persistence it is 

 easily accomplished. Also use both eyes alternately. 



17. It is well to move the object while bringing 

 it into focus. It is then easy to feel when the lens 

 touches the glass, and a moving object is seen more 

 readily than a stationary one. 



1 8. Use the plane mirror in combination with the 

 condenser, and the concave mirror without the con- 

 denser or with artificial light. 



19. In preparing stained preparations, it may hap- 

 pen that a small amount of stain remains on the upper 

 side of the cover slip. Care must be taken to focus for 

 a plane below this. 



SECTION 8 

 SCHEME FOR ROUTINE STUDY OF BACTERIA 



This scheme is to be followed strictly in the study of 

 all organisms, except when special instructions are 

 given, and the student should familiarize himself with 

 the different steps. 



i. The inoculation of one slant agar tube from each 

 rulture supplied. These inoculated agar tubes are to 



