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A MANUAL OF BACTERIOLOGY 



finger. The capsule, which should be at least one-third filled, is 

 then sealed in the flame, the dry or straight end being sealed first. 

 After coagulation, which may be hastened by placing in the warm 

 incubator for half an hour, the capsule is hung by the curved end 

 in the centrifuge and centrifuged to obtain clear serum. Little 

 change in the serum ensues for two to three days if the capsules 

 are kept sealed. The capsules may be stuck into a lump of plas- 

 ticine until required. Plasticine is useful for many such purposes, 

 for temporarily plugging tubes, etc. 



4. Suspension of the organism. In the case of tubercle, suitable 

 dead cultures can be purchased. To prepare the suspension from 

 these, a small portion of the growth (about as big as a grain of 



FIG. 36. a. Glass pipette, with india-rubber teat for opsonic deter- 

 minations, etc. ; 6 shows (enlarged) the contracted extremity of the 

 pipette ; c shows the stem of the pipette, containing the equal volumes 

 of serum, leucocytic suspension, and bacterial suspension, before 

 mixing ; d is the Wright's capsule for collecting blood. 



rice) is ground up in a small agate mortar, 1-5 per cent, salt solu- 

 tion being added drop by drop up to 2 c.c. This suspension will 

 still contain clumps, which must be got rid of by centrifuging for 

 three or four minutes. With the tubercle bacillus and gono- 

 coccus spontaneous phagocytosis is apt to occur if ordinary (0-8 

 per cent.) salt solution is used. 



A suspension of staphylococcus, streptococcus, B. coli, and 

 other organisms, is prepared by taking one or more loopfuls of 

 growth from the surface of a young agar culture and emulsifying 

 thoroughly in saline. This suspension may then be centrifuged 

 for five minutes to remove masses. The suspension' is next 

 pipetted off from the sediment and diluted to the appropriate 

 extent with saline. The suspension must not be too thick, other- 

 wise the leucocytes will take up an uncountable number of cocci ; 



