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Drs. C. Shearer and H, W. Crowe. 



substance which he calls " virulin " — presumably this attaches itself to the 

 microbes as a covering, as it is removed by washing ; thirdly, a non-virulent 

 strain of the pneumococcus may be rendered virulent by incubating it a 

 certain time in a saline extract of a virulent one. When thus treated it was 

 no longer indigestible, and would kill a guinea-pig, which he proved it 

 would not do previous to this treatment. 



His experiments, however, do not carry conviction. The loss of opsonic 

 effect which he describes might be explained by the fact that the extract in 

 which the avirulent pneumococci had lain would itself neutralise the 

 opsonin, the death of the guinea-pig being the result of the injection, 

 along with the non-virulent cocci, of some of the virulent toxins in which 

 they had been placed. He explicitly states that the washing of these cocci 

 was " rapid." It does not seem to be necessary to postulate a specific 

 " virulin " to explain the result. 



The importance of this point has led us to undertake some experiments 

 on the same lines with the meningococcus, since this organism resembles the 

 pneumococcus, in that a presumably virulent strain is not susceptible of 

 being taken up by the leucocytes. 



We can confirm Eosenow's finding up to a certain point, that a non- 

 virulent indigestible meningococcus strain, when grown in glucose-serum 

 broth to which a certain quantity of a killed freshly isolated non-indigestible 

 meningococcus culture extract had been added, is no longer taken up by the 

 leucocytes. We prefer to ascribe our finding, however, to a neutralisation of 

 the opsonic properties of the serum, by the fragments and debris of the 

 killed extract. A certain amount of this debris had been taken up by the 

 leucocytes. Moreover, if Eosenow's contention is correct, that virulence 

 depends on a specific " virulin " and that this " virulin " is taken up by the 

 non-virulent pneumococci, so that they are now transformed into proper 

 strains, that are not taken up by the leucocytes ; then if this quality is in 

 any way similar to that found under natural conditions, it should be retained 

 by these cocci on subculture. This, however, did not hold in the case of 

 our meningococci. The ingestible condition was immediately lost on the 

 first subculture. It is clear that the treatment they underwent did not in 

 any way invest them with a virulence similar to that of the freshly isolated 

 meningococcus, which invariably retains its ingestible condition through a 

 number of subcultures. 



