386 Dr. W. Bulloch and Mr. E. E. Atkin. [Jan. 10, 



Cocci per 

 leucocyte. 



1 (Control). Normal serum (2-fold dilution) + " normal " cocci + corpuscles = 25 



2 (4- )+ + =17 



3. Fluid A + +=! 



4. B + + 2'5 



5. A + cocci B' + -=27 



= 3 

 = 31 

 = 28 

 = 26-5 



6. A + B +" normal " cocci + 



7 (Control). Normal serum (undiluted) + 



8. >, + cocci A' 



9. + B' 



This experiment again shows the disappearance of the opsonin from 

 the serum at 37 and C. It also- shows (Nos. 8 and 9) that the 

 opsonin has passed into the cocci (A' and B'). 



2. 



In this experiment an attempt was made to determine whether 

 at C. a complement-like body could be separated out, which, with 

 heated serum, would exert an opsonic effect. 



Technique. 1. Normal serum mixed with emulsion of cocci, in equal 

 parts, at C. for 15'. The mixture was then centrifugalised, and 

 separated into a supernatant fluid (A) and a deposit (A'). 



2. Serum heated to 60 C. for 15', mixed with cocci (aa), and placed 

 at C. for 15'. It was then centrifugalised, and separated into a 

 supernatant fluid (B), and a deposit (B'). Controls were supplied by 

 normal serum (in appropriate dilutions), digested with " normal " cocci 

 and corpuscles at 37 C., and heated serum under the same conditions. 



Cocci per 

 leucocyte. 



1 (Control). Normal serum (2-f old dilution) + " normal" cocci + corpuscles = 25 



2 (4-fold ) + + =18 



3 Serum heated to_60 C. for 15' + + = 2 



4. Fluid A + heated serum (aa) + + =2 



5. Fluid A + _+'.! 



6. cocci A' + =22 



cocci B' = 4 



Remarks. This experiment shows that the opsonin is very different 

 in type from a lysin, as apparently no complement-like body remains 

 in the supernatant fluid after the serum has been digested at C. 

 The low reading in the case of the deposit B' would also lead to the 

 supposition that the action of heat at 60 has been to destroy the 

 opsonin altogether. This supposition ia confirmed by the following 

 experiment. 



If heated serum is unable to exert an opsonic action on staphylococci, 

 are the latter, when digested with heated serum, capable of being 

 opsonised by unheated serum 1 



