172 CLINICAL BACTERIOLOGY AND HEMATOLOGY 



The Process.— 1. Prepare a pipette by placing an indiarubber 

 nipple on the thick end. Then with a grease pencil or with pen 

 and ink make a transverse line about i inch from the pointed end. 

 The volume of fluid contained in the tube between the point and 

 this mark is spoken of as the unit. 



2. Having the patient's serum, the emulsion of leucocytes, and 

 the emulsion of bacteria, ready in front of you, take the pipette 

 between the index-finger and thumb of the right hand, and com- 

 press the nipple. Immerse the point beneath the surface of the 

 emulsion of bacilli and relax the pressure on the nipple until the 

 emulsion has risen exactly to the mark, so that you have drawn 

 up one unit ; then remove the point from the fluid and relax the 

 pressure again, so that a small column of air will be sucked up. 

 This will be quite easy if the point is a good one ; otherwise it will 

 be difficult or impossible, as the column of fluid will either refuse 

 to stir or will oscillate violently. 



Fig, 34. 



Fig. 35. 



Next immerse the point in the emulsion of leucocytes and draw 

 up one unit. This will be separated from the emulsion of bacteria 

 by the short column of air. Remove the point from the emulsion 

 and draw up a second column of air ; reinsert it and draw up 

 a second unit of leucocytes, and then a third column of air. 



Lastly, draw up one unit of the serum. You will then have in 

 your pipette (counting from the nipple towards the point) one unit 

 of bacterial emulsion, a column of air, a unit of leucocytes, a 

 column of air, a second unit of leucocytes, a column of air, and, 

 lastly, a unit of serum (Fig. 34).* 



3. Put the point of the pipette on to a clean slide and express 

 the whole of its contents, and mix them well together, sucking 

 them repeatedly into the pipette and expelling them. When 

 thoroughly mixed suck them into the pipette, suck up a short 

 column of air, and seal the tip in the flame (Fig. 35). 



* It is not necessary to take more than one unit, and where many estima- 

 tions are being made one only should be employed, as less "cream" is 

 required. 



