THE OPSONIC INDEX 



215 



coagulation, which may be hastened by placing in the 

 warm incubator for half an hour, the capsule is hung Ly 

 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 plasticine until required. 



FIG. 35. a. Glass pipette, with india-rubber teat for opsonic 

 determinations, 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. 



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 rice) is ground up in a small 

 agate mortar, 1-5 per cent, salt solution 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 staphylococcic suspension is prepared by taking an 

 agar culture not more than twenty- four hours old, adding 

 salt solution (0-8 per cent.), and shaking gently so as to 

 wash off the growth. When the suspension is made it 



