1905.] On the Opsonic Action of the Blood Serum. 387 



Experiment. 



Technique. Normal serum was heated to 60 C. for 15', then mixed 

 with an equal quantity of staphylococcus emulsion, and digested at 

 37 C. for 15', the deposit of cocci. (A) being then removed by the 

 centrifuge. 



The deposit (A) was then divided into two parts, one being reserved 

 for the opsonic test, the other being mixed with normal serum. The 

 mixture was digested for 30' ; the centrifuge was then applied, so as 

 to separate a supernatant fluid (B) from a deposit of cocci (B'). 

 Results. 



Cocci per 

 leucocyte. 

 1 (Control). Normal serum + normal cocci + corpuscles = 18 '6 



2. (2-fold dilution) + + =16 



3. Heated serum + + ?) _ Q .5 



4. Normal serum + cocci A + = 15 '5 



5. Fluid B + normal cocci + = '4 



6. cocci B' + ,, =15 



This experiment bears out the suggestion above, that heat destroys 

 the opsonin. The cocci (A) having been quite uninfluenced by the 

 heated serum, were capable of being opsonised by normal serum, and 

 they were further, as shown in No 5, capable of abstracting all the 

 opsonin out of normal serum. After being acted on by the normal 

 serum, the mere addition of corpuscles demonstrated that they had 

 been acted upon by the opsonin (No. 6). 



1 . Opsonin is present in the normal serum. 



2. Opsonin is thermolabile. 



3. It rapidly disappears from the serum when the latter is mixed 

 with bacteria at 37 C. or at C. 



4. After the opsonin has united with the bacteria the mixture of 

 serum and cocci can be heated to 60 C. for long periods without 

 abolition of the opsonic effect. 



5. The leucocyte is practically an indifferent factor when the 

 phagocytic power of different bloods is compared. 



6. The capacity of bacterial emulsions for extracting opsonin from 

 the serum is only slightly diminished by subjecting these emulsions 

 to very high temperatures over prolonged periods. 



7. The action of heat is to destroy the opsonin, and not merely to 

 convert it into a non-opsonisable modification. 



8. The opsonin is not identical with any of the anti-bodies hitherto 

 discovered in the serum. 



9. The opsonin is of relatively simple constitution ; where these 

 experiments cover the same ground as those of Wright and Douglas, 

 the observations of these authors are confirmed. 



