258 FUNDAMENTAL EXPERIMENTS ON OPSONINS 



The first experiment is to determine whether leucocytes thus 

 free from serum are able to ingest bacteria. To this end they 

 are mixed with an emulsion of staphylococci or tubercle bacilli, 

 enclosed in a capillary tube and incubated at 37 C. for a quarter 

 of an hour. At the end of that time the emulsion is expelled, and 

 films are prepared and stained in the ordinary way. It will be 

 found that the leucocytes have taken up very few bacteria, if any. 

 It is obvious, therefore, that phagocytosis goes on to a very small 

 extent in the absence of serum. Some species of n on -pathogenic 



9Y..; 4 

 # 



FIG. 56. ON THE LEFT, A PORTION OF AN OPSONIN FILM (OF PNEUMOCOCCI) ; 

 ON THE RIGHT, A PORTION OF A SIMILAR FILM, TAKEN FROM A PREPARA- 

 TION IN WHICH NO SERUM WAS USED. (Original.) 



bacteria are taken up well in the absence of serum, and one micro- 

 coccus which I have met with was not ingested under any circum- 

 stances whatever. 



Secondly, a mixture similar to the above is prepared, but with 

 the addition of one volume of serum, so that the mixture consists 

 of an equal volume each of leucocytic emulsion, bacterial emul- 

 sion, and serum. This is incubated and examined as above, and 

 it will be found that many bacteria are taken up ; the number 

 depends on the thickness of the emulsion and on the source of the 

 serum, but if the former be rich and the latter potent there may 

 be an average of twenty or even far more per polynuclear. The 

 bacteria which are not ingested show no signs of digestion, there 

 being no loss of sharpness of contour or of staining activity. 



