204 CLINICAL BACTERIOLOGY AND H^MATOLOGY 



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. 36).* 



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. 37). 



Then place the pipette in the incubator at 35 to 37 C, 

 noting the time exactly, and proceed to prepare a second 

 pipette in exactly the same way, using the same emulsions 

 of bacteria and leucocytes, but the control serum instead of 

 the patient's. Place this in the incubator by the side of the 

 other, noting the time at which you do so. When no incuba- 

 tor is at hand the tubes may be placed in a vessel of water, 

 which can be kept at blood-heat for the necessary time (fifteen 



FIG. 36. 



f^a. - t s>*^ > *^V* 



FIG. 37. 



minutes) with very little trouble, or the Dewar flask previously 

 mentioned may be used. 



When each pipette has been incubated for a quarter of an 

 hour, remove it from the incubator, break off the end, fit the 

 nipple to the thick end, and expel the contents on to a clean 

 slide. Next mix them thoroughly together. Then prepare 

 suitable films in the usual manner. The best method is to 

 make use of a "spreader," which is made by notching a thin 

 slide by means of a file at two points opposite one another, 

 and breaking it between the two points. It is necessary that 

 the spreader should be very slightly concave, and to secure 

 this several slides may have to be broken. When a piece with 

 a suitable curvature has been prepared, cut or file off a small 

 piece at each corner, so that the smear it makes is decidedly 



* 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. 



