Specificity of the Opsonic Substances in the Blood Serum. 531 



The points of the chitinous ribs which strengthen the segments of the 

 ovipositor project above the upper border of the segment, and to them are 

 attached the muscles of the ovipositor. The narrowed terminal portion of 

 the rectum enters the ovipositor on the dorsal surface of the uterus and runs 

 down to the anal opening between the external plate and the last segment. 



The Specificity of the Opsonic Substances in the Blood, Serum. 

 By William Bulloch, M.D., and G. T. Western, M.A., M.B. 



(Communicated by Leonard Hill, F.E.S. Eeceived February 15, — Read 



March 1, 1906.) 



(From the Bacteriological Laboratory, London Hospital, E.) 



A relatively high degree of specificity has been demonstrated for most of 

 the antibodies which exist in immune sera, e.g., in the case of agglutinins, 

 lysins, precipitins, antitoxins. With normal sera the proof of specificity is 

 often difficult on account of the fact that the antibodies are present in the 

 majority of cases only in small quantities. 



The following experiments are concerned with the specificity of the 

 opsonic substances of normal and immune sera. As is well known, these 

 opsonic substances, discovered by Wright and Douglas, act on bacteria 

 in such a way that the latter become an easy prey to the phagocytic 

 leucocytes. 



If a given serum be tested it will be found to exert an opsonic action on 

 more than one kind of bacterium, and the question we have sought to 

 answer is whether there is one or more than one opsonic substance ; in 

 other words, whether the opsonins are specific for the different bacteria on 

 which they exert their opsonic action. 



In a previous communication* one of us (B.) has shown that when a 

 microbe, e.g., staphylococcus, is digested with normal serum at 37° C. for 

 15 minutes, and the cocci are then brought down by the aid of a centrifuge, 

 the supernatant liquid is found to be devoid of opsonic action for staphylo- 

 cocci. Where the contact of the microbe with serum has been sufficiently 

 long, and the centrifugalisation has been complete, the opsonin for the 

 particular microbe is totally removed. 



* ' Boy. Soc. Froc.,' vol. 74. 



