64 CLINICAL BACTERIOLOGY AND 



into a small tube, centrifugalized for a few minutes to assist 

 in breaking down the clumps, chains, etc., and then well 

 shaken, after sealing the tube, as described on p. 51, Fig. 24. 

 This emulsion should be of a faint opalescent colour. 



If too many bacteria are in emulsion, it may be almost 

 white, in which case it is too rich, and the leucocytes will 

 take up an excessive number of bacteria, which will render 

 the field difficult to count. Such an emulsion should be 

 further diluted. 



3. Prepare an emulsion of living leucocytes in the 

 following manner : Take about 10 c.c. of normal saline 

 solution, and add i per cent, sodimn citrate solution to 

 prevent coagulation, of the blood j* place this in a centri- 

 fugalizing tube and voarm to blood heat. Then prick the 

 facial vein of the healthy animal and drop into the tube 

 1 or 2 c.c. of blood. This is now put into the centrifuge 

 and centrifugalized about fifteen minutes, until all the 

 corpuscles have gone to the bottom and the supernatant 

 liquid is left clear. 



The deposit will show the red corpuscles at the bottom, 

 and on the top a thin grey layer of leucocytes. Now 

 aspirate the clear fluid with a capillary pipette and teat, 

 taking care not to disturb the layer of leucocytes. 



This done, suck up the leucocytic layer and some of the 

 red corpuscles, and put them in a small tube, thoroughly 

 mixing them with the pipette, giving an emulsion of 

 living leucocytes and a few red corpuscles. 



4. Take two Wright's pipettes, with rubber teats, and 

 with a grease pencil mark the glass stem at its distal end 

 \ to 1 inch from the point. Fluid taken up to this mark 

 constitutes one unit volume. 



We should now have in front of us on the laboratory 

 table a slab of plasticine, fixed into which are (a) a small 



* Burroughs Wellcome and Co. make convenient soloids of the 

 following formula : 



Sodii chloridi ... ... ... ... 0-075 gm. 



Sodii citratis ... ... ... ... 0'05 gm. 



