558 IDENTITY OF OPSONINS WITH NORMAL AGGLUTININS, 



in the human blood, we know little or nothing beyond the fact 

 that they are present in relatively small amount. 



It is generally supposed that the effect of moderate heat upon 

 the agglutinins is to partially destroy them, but Dreyer found 

 that coli agglutinin which had lost much of its power by heating 

 exhibited its full power if the agglutination test was prolonged 

 for 24 hours, and from this he concluded that the action of heat 

 consisted in a slowing of the reaction between the agglutinin and 

 the bacterial agglutinable substance. I believe this to be the 

 true explanation. Typhoid agglutinin is certainly not destroyed, 

 for I found that suspensions of typhoid bacteria treated with 

 heated agglutinating serum beyond the limiting ratio for the 

 heated serum were sedimented easily by the centrifuge, while 

 neither normal suspensions nor those treated with unheated 

 serum beyond the limiting ratio were so easily precipitated. 



Those who have worked with opsonins have not examined the 

 time factor in opsonisation, and it occurred to me that if instead 

 of 15 minutes, 24 hours were given for the heated opsonin to act, 

 phagocytosis might be obtained. 



As it would be necessary to check vegetative growth in 

 experiments that were to continue for 24 hours, the cells in the 

 suspension of Micrococcus aureus (derived from a whitlow) were 

 steamed for 10 minutes.* The suspension was then centrifuged 

 to get rid of any small clumps that might have formed. The 

 washed leucocytes were obtained in the manner recommended by 

 Wright and Douglas, which has been described in these pages 

 {a7itea, p. 296). The proportions of corpuscles, bacterial suspen- 

 sion and serum were measured and treated as by these investi- 

 gators excepting where otherwise noted. 



The heated serum was mixed with the bacterial suspension in 

 the proportion of 3 : 1 and sealed in a capillary tube which was 

 heated for 20 hours at 37°. It was then mixed with the cor- 

 puscular suspension in the proportion of 4 : 3. A control test 

 was made with the same serum, unheated, which had been kept 



* When the temperature of a control tube was 94°. 



