LVI. Counting red corpuscles. 



/. Appliances. Microscope with one- seventh inch objec- 

 tive, and a mechanical stage; needle and holder; Thoma- 

 Zeiss counter. 



2. Preparation. (1) The counter and pipette should be care- 

 fully cleaned with water, followed by alcohol and thor- 

 oughly dried. (2) Prepare the following solution for 

 diluting blood : 



Sod. sulph gm. 107 



Aqua dist c c. 120 



j. Operation. Obtain the blood as described in Lesson LV, 

 allowing it to collect until almost ready to drop. Then 

 insert point of pipette into the drop and by sucking gently 

 draw the blood up to the mark 0.5. Wipe the end of 

 the pipette and insert it into the diluting solution, sucking 

 it up until the bulb is filled to the mark 101. Close 

 ends of pipette with fingers, rolling and shaking it about 

 for a minute. Blow out three drops of the diluted blood. 

 Then drop from the pipette on the round table of the coun- 

 ter just enough of the dilution to cover it when the cover is 

 placed upon it without causing any of the liquid to flow 

 over into the moat. (Fig. 38b). Place the counting 

 slide under the microscope and find the upper left hand 

 square; count all the corpuscles in it. Then count the 

 next square to the right and continue until all the upper 

 row has been counted; write down the number of cor- 

 puscles. Then move the counter so that the next lower row 

 can be counted from right to left continuing until all the 

 squares are counted. Clean the counter; agitate the 



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