366 Dr. A. E. Wright and Capt. S. li. Douglas. [Sept. 1, 



EXPERIMENT 3. 



A. S. K. D.'s inactivated serum, 3 vols. ; staphylococcus suspension 

 (previously heated to 75 C. and cooled), 1 vol. ; digested together for 

 15 minutes at 37 C. 



4 vols. of the above added to 3 vols. of S. R. D.'s corpuscles. 



Phagocytic power (bacteria in 30 P.W.B.C. counted and 

 averaged) 4'2 



B. S. K. D.'s unheated serum, 3 vols. ; staphylococcus suspension 

 (previously heated to 75 C. and cooled), 1 vol. ; digested together for 

 15 minutes at 37 C., then heated for 10 minutes to 60 C., and 

 cooled. 



4 vols. of the above added to 3 vols. of corpuscles. 



Trie 1. Phagocytic power (bacteria in 15 P.W.B.C. 



counted and averaged) 28 2 



Tube 2. Do. do. 31-0 



We have here conclusive proof that the blood fluids modify the 

 bacteria in a manner which renders them a ready prey to the 

 phagocytes. 



We may speak of this as an " opsonic " effect (opsono / cater jar ; 

 I prepare victuals for), and we may employ the term " opsonins " to 

 designate the elements in the blood fluids which produce this effect. 



DOES THE UNHEATED SERUM CONTAIN, IN ADDITION TO ELEMENTS 

 WHICH RENDER THE BACTERIA MORE LIABLE TO PHAGOCYTOSIS 

 (OPSONINS), ALSO ELEMENTS WHICH DIRECTLY STIMULATE THE 

 PHAGOCYTES (STIMULINS) 1 



We have sought to elucidate this question by three separate 

 methods. 



In a first series of experiments, we experimented with staphylococci 

 which had been exposed to high temperatures (115 C.) with "the design 

 of rendering them insusceptible to the opsonic power of the blood 

 fluids. Our expectations from this method expectations based on the 

 fact that we had noticed that typhoid bacilli acquired, when heated to 

 over 70 C., a resistance to the bacteriolytic effect of the blood fluids 

 were unrealised. We found that the quantitative differences between 

 the phagocytosis in heated and unheated serum respectively were not 

 less in the case of staphylococci which had been exposed to a tempera- 

 ture of 115 C., than in the case of staphylococci which had not been 

 subjected to high temperatures. 



In a second series of experiments we substituted for suspensions of 

 staphylococci suspensions of particles, which we assumed would be 

 uninfluenced by the opsonic power of the blood. The results of these 



