218 A MANUAL OF BACTERIOLOGY 



brought near will quickly dispel them. When thoroughly 

 mixed, aspirate the mixture into the pipette, suck up a 

 short volume of air, and seal the tip in the flame. 



Then place the pipette point downwards in the incubator, 

 or better, in a water-bath at 35 to 37 C., noting the 

 time exactly, and proceed to prepare a second pipette in 

 precisely the same way, using the same suspensions of 

 bacteria and leucocytes, but the control serum instead of 

 the patient's. Place this in the incubator or water-bath, 

 by the side of the other, noting the time at which this is 

 done. When each pipette has been incubated for a quarter 

 of an hour it is removed from the incubator or water-bath, 

 the end broken off and the nipple fitted to the thick end ; 

 then the contents are expelled on to a hollow slide or 

 porcelain palette and mixed thoroughly together. Films 

 are then prepared. This may be done by depositing a 

 drop in the middle of a large cover- glass (1-inch squares, 

 No. 2), dropping on to it another cover- glass and drawing 

 the two apart. Or the films may be made on slides, for 

 which Wright recommends roughing the slides with fine 

 emery paper and spreading the film with the sharp edge 

 of a broken slide (see next page). The films then have to 

 be stained. For staphylococci, streptococci, pneumococci, 

 B. coli, etc., the films may be fixed with formalin and 

 stained with carbol-thionine blue or borax-methylene blue 

 (see " Malaria "), or they may be stained without previous 

 fixing with the Leishman stain. For tubercle, the films 

 may be fixed in a saturated solution of mercuric chloride 

 (one or two minutes), stained in warm carbol fuchsin, 

 decolorised with 2J per cent, sulphuric acid in methylated 

 spirit, and counterstained with methylene blue. 



Wright now uses the whole blood instead of the leuco- 

 cyte layer only. After the blood has been drawn into the 

 titrated salt solution it is centrifuged, washed twice with 

 salt solution, the fluid is pipetted off, and finally the 



