RESEARCHES ON CERTAIN PROBLEMS OF fLAGtJE IMMUNITY 4! 



a positive chemiotaxis. The substance producing the change has been 

 variously designated as fixateur, substance sensibiHsatrice, opsonin and 

 incitor. 



It is still an open question whether we are here dealing with a stage 

 in an incomplete bacteriolysis in which the amboceptor acts as the 

 intermediary between the bacillus and the leucocyte. The view is one 

 which can be maintained with much reason. Certain organisms, such as 

 the Cholera vibrio, when acted on by an immune serum containing 

 amboceptor and complement, undergo bacteriolysis, which can be seen 

 under the microscope, or estimated by the absence of growth. Other 

 organisms, such as the B. pestis, are acted on by an immune serum, 

 but in this case the solution or death of the bacillus does not take place 

 outside the cells. That the organism has, however, suffered change 

 is shown by the altered behaviour of the leucocytes to which we have 

 just referred. 



Whether the bacillus undergoes an extra-cellular bacteriolysis, or 

 is digested after being phagocytosed, it must not be overlooked, that 

 in both cases it is highly probable that the ultimate protection of the 

 animal is effected by the phagocytes, which, in the former case, take 

 up the toxic particles set free by bacteriolysis, in the latter, take up and 

 digest the bacillus and retain the toxic particles liberated during the 

 process. 



When the extra-cellular or intra-cellular bacteriolysis is carried on 

 with too great energy so that the leucocytes are not strong or numerous 

 enough to deal with the toxic products, the death of the animal results. 



The question as to whether anti-plague serum owes any of its 

 protective power to the " stimulines " of Metchnikoff and the " anti- 

 aggressins" of Bail must be decided by further investigations. 



Conclusions. 



1. That toxins can be obtained from broth cultures of the plague 

 bacillus. 



2. That these toxins are probably endotoxins, as the toxicity of the 

 filtrate increases with the age of the culture, and becomes considerable 

 only after many of the bacilli have been autolysed. 



(151) 



