284 INFECTION AND IMMUNITY 



destruction OF alteration of the " opsonophore " group. This view is 

 not shared by all workers and has been disputed by Bullock and Atkin. 1 

 The Technique of Wright. The three factors necessary for the per- 

 formance of an opsonic test are (1) the blood serum to be tested; (2) 

 an even emulsion of bacteria, and (3) leucocytes. 



(1) Blood serum is obtained by bleeding from the finger and receiving 

 the blood into glass capsules (Fig. 66). These are sealed at both ends; 

 the blood is allowed to clot ; and the separation of serum is hastened by 

 a few revolutions of a centrifuge. 



(2) The bacterial emulsion is obtained by rubbing up a few 

 loopfuls of a twenty-four-hour slant agar culture with a little physio- 

 logical salt solution (0.85 per cent) in a watch glass. A very small 



amount of salt solution is used at first 

 and more is gradually added, drop by 

 drop, as the emulsion becomes more 

 even. The final breaking up of the 

 smaller clumps is best accomplished by 



cutting off very squarely the end of a 

 FIG. 66. WRIGHT'S CAPSULE FOR ' . J 



COLLECTING BLOOD. capillary pipette, placing it perpen- 



dicularly against the bottom of the 



watch glass, and sucking the emulsion in and out through the narrow 

 chink thus formed. (Fig. 67.) 



Emulsions of tubercle bacilli are more difficult to make. The bacilli 

 filtered off in the manufacture of old tuberculin are commonly used. 

 These are washed in salt solution on the filter, and are then scraped off 

 and sterilized. They are then, in a moist condition, placed in a mortar 

 and thoroughly ground into a paste. While grinding, salt solution 

 1.5 cent) is gradually added until a thick emulsion appears. This 

 emulsion may be diluted and larger clumps separated by centri- 

 fugalization. . . 



(3) The leucocytes are obtained by bleeding from the ear or finger 

 directly into a solution containing eighty-five hundredths per cent to one 

 per cent of sodium chlorid and five-tenths to one and five-tenths per cent 

 of sodium citrate. Ten or fifteen drops of blood to 5 or 6 c.c. of the 

 solution will furnish sufficient leucoc}^tes for a dozen tests. This 

 mixture is then centrifugalized at moderate speed for five to six minutes. 

 At the end of this time, the corpuscles at the bottom of the tube 

 will be covered by a thin grayish pellicle, the buffy coat, consisting 



1 Bullock and Aikin, Proc, RoyaJ Soc., Ixxiv, 1905. 



