184 PHAGOCYTOSIS OPSONINS AND BACTERIOTROPINS. 



Streptococci may similarly be rubbed up in a mortar with 0.85 per 

 cent, salt solution and then centrifugalized. As a rule, however, vigorous 

 pipetting into a watch glass with subsequent centrifugalization for a few 

 minutes is sufficient to remove the chains and leave a satisfactory emulsion. 



If several specimens of blood are to be examined it is best to put up a 

 "trial trip" and do a preliminary phagocytic count in order to test the 

 strength and condition as regards clumping of the emulsion. The phagocy- 

 tic count should be for tubercle between 1.5 to 2 per cell and for other organ- 

 isms not less than 3 per cell. Accordingly, further dilution or concentration 

 of the emulsion is necessitated. The pipettes employed for the opsonic 

 index should be about 16 cm. long and made from glass tubing about 5/16 

 of an inch in diameter. They should all be approximately of the same 

 caliber and but slightly tapering toward the point. The piece of tubing 



FIG. 25. 



should tightly fit the rubber nipple 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 mixture is drawn up 

 into the pipette, the end sealed in a small pilot flame, the pipette placed into 



