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CLINICAL BACTERIOLOGY AND HiEMATOLOGY 



downwards until it almost touches the cover-glass ; look down the 

 microscope and focus gently upwards, using the fine adjustment, 

 and keeping a careful look-out for the rulings. 



If the rulings of the slide are indistinct, they may be darkened 

 by rubbing them with a very soft lead-pencil. 



5. Counting the Corpuscles. — Move the slide about until you have 

 come to one corner (preferably the left upper corner) of the ruled 



Fig. 43. — The "Bars" which are to be Counted are Shaded. 



area. You will see that each fifth space is marked off by a line 

 running down its centre ; this is to guide the eye and facilitate 

 counting. The whole square consists of four hundred small 

 squares, twenty along each side. You have to count at least a 

 hundred of these small squares. The simplest way to do this is 

 to count five " bars " of twenty each, each bar extending right 

 across the ruled " chess-board," The bars selected should be as 



