

PREPARATION OF SMEAR 



207 



mately of the same caliber and but slightly tapering toward the point. 

 The rubber nipple should tightly fit the piece of tubing or bulb available. 

 For use, the capillary end should be cut square and the pipettes marked 

 with a paraffin pencil about 3/4 of an inch from their extremity. The 

 content as far as this mark is the unit of volume in each case. 



The rubber nipple is now held between thumb and forefinger and 

 gently compressed, the capillary end introduced into the well-mixed 

 blood cells and the unit volume drawn up by slightly relaxing the pressure 

 on the bulb. Next a tiny bubble is allowed to enter, then an equal volume 

 of the emulsion, followed by another tiny bubble which latter is succeeded 

 by an equal volume of serum. By gentle pressure on the bulb the several 

 volumes are ejected upon a clean glass slide, and thoroughly mixed by 

 alternately sucking the mixture into the pipette and squeezing it out again 

 upon the slide. It is enough to repeat this action three times. Then the 



FIG. 26. 



mixture is drawn up into the pipette, the end sealed in a small pilot flame, 

 the pipette placed into the opsonizer (Fig. 24) and the time noted. This 

 operation is repeated with each serum. 



Coliform organisms and" the gram negative cocci should be incubated 

 not longer than six to eight minutes. Tubercle bacilli and other organisms 

 require fifteen minutes, more or less according to the strength of the 

 emulsion. 



The pipettes are withdrawn in the same order in which they were 

 placed in the opsonizer. The contents of each are blown out on to a 

 slide, and very carefully mixed as before (Fig. 25). The entire quantity 

 is divided between two or three slides and several smears are made, the 

 best one being selected for counting. These slides should previously have 

 been roughened with very fine (oo) emery paper and cleaned with a duster, 

 and should rest on their concave surface so that the smear is made on the 

 convex side. (It will be noticed that a slide can be made to rotate if 

 resting on one surface (convex), but does not do so when resting on 

 the concave surface.) The smears are best made by means of a 

 broken slide with a slightly concave edge. This "spreader" (Fig. 26) is 

 made by sharply breaking a glass slide at about its middle, this being 



