400 Mr. G. Dean. Enquiry into the Nature of the [Apr. 23. 



The Influence of the Strength of the Emulsion upon the Number 

 of Organisms taken up by the Leucocytes. 



In Table I are shown the results obtained in two experiments carried out 

 in the usual way by mixing one volume of serum, one volume of washed 

 blood corpuscles and one volume of bacterial emulsion, putting the pipettes 

 containing the mixtures in the incubator at 35°*5 C. for 15 minutes, 

 after which the preparations for microscopical examination were made. 

 The number of phagocytosed bacteria were subsequently counted, and the 

 average number per leucocyte taken as the phagocytic index. As a rule, the 

 number of organisms in 50 to 80 leucocytes were counted, and in many 

 of the experiments the mean of two or three such counts by independent 

 observers was taken. The emulsion of Staphylococcus pyogenes aureus was 

 employed in different concentrations, full strength, half strength, quarter 

 strength, one-eighth strength, and one-sixteenth strength. 



Table I. 



Emulsion of cocci 

 concentration. 



Average number of cocci phagocytosed in the 

 case of — 



Thick emulsion. 



Thin emulsion. 



1 



j, 



2 



4 



1 

 8 



T6 



86-0 



52-5 



17 4 



7-9 



3-0 



16-5 

 9-6 

 6-4 

 2-9 

 1-3 



The number of organisms taken up is, within the error of experiment, 

 directly proportional to the concentration of the bacterial emulsion 

 employed. 



Influence of Dilution of the Serum upon the Number of Organisms 

 taken up by the Leucocytes. 



When in similar experiments different concentrations of the same normal 

 serum are employed, no direct proportionality can be demonstrated to exist 

 between the serum concentration and the number of microbes phagocytosed. 

 For example, the number of ingested organisms may be as great, or even greater, 

 with the half, quarter, or even the one-eighth concentration, as with the full 



immune body, when aided by complement, may act more powerfully, and that the sudden 

 fall in the " opsonic " power of both normal and immune serum, on heating, is due to the 

 destruction of the complement. I may revert to this subject on another occasion." 



