384 



Dr. W. Bulloch and Mr. E. E. Atkin. 



[Jan. 10, 



We have already seen that a temperature of 60 C. applied to the 

 serum suffices to abolish its opsonic effect. Wright and Douglas 

 showed, however, that if the serum were first brought into contact with 

 bacteria at 37 C. for 15', and the mixture were then heated to 60 C. 

 for 15', the cocci were picked up by leucocytes without difficulty. It 

 was upon this experiment that they based their conclusion that the 

 opsonin really acts upon the bacteria and does not merely stimulate the 

 leucocyte. We have thought it important to determine whether pro- 

 longed heating at 60 C. of opsonised cocci can destroy the opsonic 

 power so that these cocci cannot be picked up subsequently by leuco- 

 cytes. 



Experiment. 



Technique. Normal serum (three parts) mixed with staphylococcus 

 emulsion (one part) ; mixture kept in water bath at 37 C. for 15'. 

 This mixture, which is spoken of below as " opsonised cocci," was then 

 distributed into a series of glass pipettes which were placed in the 

 water bath at 60 C. for periods of 15' up to 5 hours. On 

 removal from the water bath, four volumes of the " opsonised cocci " 

 were mixed with three volumes of corpuscles at 37 C. for 15', and the 

 phagocytic count made as usual. For comparison the phagocytic count 

 of unheated serum + cocci, and of serum heated to 60 C. before being 

 mixed with cocci, is added. 



Results. 



Cocci per 

 leucocyte. 



1. Unheated serum (3 vols.) + cocci (1 vol.) + corpuscles (3 vols.) = 28 



2. Serum heated to 60 C. for 15'+ + 



3. " Opsonised cocci " at 60 C. for 15' (4 vols.) + 



4. 



5. 



6. 



7. 



8. 



9. 

 10. 

 11. 



30' 

 45' 

 60' 

 H hrs. 

 2 



= 27 

 = 28 

 = 23 

 = 24-5 

 = 23 

 = 23-5 

 = 22 

 = 24 

 = 23-5 



The experiment shows that some change is produced in the bacteria 

 during the 15' exposure at 37 C. and the change is such that sub- 

 sequent heating to 60 for even 5 hours is inoperative, this being very 

 different to the effect of a preliminary heating of serum at 60 C. 

 before admixture with bacterial emulsion. 



Experiments on the rate of disappearance of opsonin from serum 

 when the latter is brought into contact with cocci at 37 C. and 

 at C. 



