RESEARCHES ON CERTAIN PROBLEMS OF PLAGUE IMMUNITY 37 



The subject with especial relation to plague has been studied among 

 others by Denys and Tartakowsky (1900), who attributed the anti- 

 microbial action to the influence exerted by the serum on the process of 

 phagocytosis. 



Bordet and Gengou (1901) demonstrated the presence of substance 

 sensibilisatrice in anti-plague serum by their method which is based on 

 the observation that only sensitised bacilli are capable of removing alexin 

 or complement from a fresh serum. The haemolysis of sensitised red 

 blood corpuscles is used as the test for free complement. 



Employing this method, they showed that plague bacilli, which 

 had been in contact with heated immune serum, removed the complement 

 from fresh serum, and must, therefore, have been sensitised. These 

 authors point out that certain micro-organisms, such as the B. pestis, 

 are capable in this way of absorbing complement without undergoing any 

 morphological changes, though the possibility of a physiological change 

 having been effected is not excluded. 



Markl (1903) made a very thorough investigation into the mechanism 

 of the action of anti-plague serum. He found that all the phenomena 

 could not be explained on the assumption that the serum had a 

 bacteriolytic action, since bacteriolysis takes place only in the case 

 of bacilli of low virulence. When he submitted plague bacilli in vitro to 

 the action of an immune serum which had been reactivated by fresh 

 normal serum, and made microscopical preparations at intervals of time, 

 he found that the bacilli showed no marked changes such as would 

 indicate that they had suffered any harm. On the other hand, if, in place 

 of the normal serum, he used peritoneal lymph containing leucocytes, he 

 found the leucocytes packed with bacilli which lost their normal staining 

 reaction, and, at the end of 12 hours, in the case of bacilli of moderate 

 virulence, the bacilli were represented only by dust-like detritus. Markl 

 holds that, in the case where peritoneal lymph, rich in leucocytes, is used 

 to reactivate the immune serum, not only is there great destruction of the 

 bacilli within the leucocytes, but there occurs extra-cellular destruction of 

 the bacilli which is inversely proportional to the virulence of the bacillus. 

 When a highly virulent plague culture is injected intraperitoneally 

 the multiplication of the bacilli can be followed. There is very little 

 exudate, in which only a few leucocytes are present, and there is a rapid 

 increase in the number of bacilli followed by death in 24 hours. 



(147) L I 



