PHAGOCYTOSIS AND VIRULENCE. 



315 



If an animal is susceptible to a virulent culture 

 of anthrax, but resistant to a weak culture, the 

 phagocytic power is found to be greater for the 

 weaker organism. The highly virulent culture 

 creates a condition of negative chemotaxis, with 

 the consequence that leucocytes are not attracted 

 and microbic proliferation proceeds rapidly. 

 Without going into details, studies of the follow- 

 ing and perhaps other micro-organisms have 

 strengthened Metchnikoff in his views: staphylo- 

 cocci, streptococcus, pneumococcus, gonococcus, 

 vibrio of cholera in infections of the guinea-pig, 

 the vibrio of goose septicemia in relation to the 

 guinea-pig, which is naturally immune, the spi- 

 rillum of relapsing fever, tubercle bacillus, yeast 

 cells and other fungi, and certain animal para- 

 sites (Trypanosoma lewisii). 



Most important are certain conditions which 

 create a condition of negative chemotaxis, or other- 

 wise engage the phagocytes so that they refuse to 

 take up the essential organism. Vaillard says 

 that all animals are immune to pure cultures of 

 the tetanus bacillus or its spores, provided the lat- 

 ter have been washed entirely free of toxin. The 

 absence of toxin permits of positive chemotaxis 

 and phagocytosis, whereas toxin when present 

 causes negative chemotaxis, and the bacilli pro- 

 ceed to further toxin formation. The same is held 

 to be true in infections by some other organisms. 



It seems to be definitely established that con- 

 taminating organisms (pyogenic cocci, Bacillus 

 prodigiosus) may greatly increase the virulence of 

 the bacillus of symptomatic anthrax, Bacillus 

 Welchii, and the tetanus bacillus anaerobic or- 



Relatioii of 

 Phagocytosis 

 to Virulence 

 of Bacteria. 



Toxins as 

 Cause of 

 Negative 

 Chemosis. 



Accidental 

 Engagement 

 of Phago- 

 cytes. 



