170 Chapter VI 



solely because of the occurrence of very pronounced phagocytosis. 

 Such an injection is soon followed by a very marked invasion of 

 leucocytes which cram themselves with spores and bacilli without 

 being in any way inconvenienced thereby (Fig. 37). Once the phago- 

 cytes have devoured all these organisms, the latter become incapable 

 of producing their morbific effect. The spores cannot germinate 

 within the phagocytes, but there undergo a marked degeneration 

 and finally, after a longer or shorter interval, disappear. 



When, on the other hand, the tetanus bacilli or their spores are 

 accompanied by the pre-formed toxin, the latter, according to Yaillard, 

 excites a negative chemiotaxis of the leucocytes which keep away 

 from the organisms and which are thus allowed to multiply and 

 to secrete fresh quantities of toxin. The natural immunity of the 

 animal's organism against the tetanus bacillus can be suppressed 

 whenever the phagocytic defence is hampered in any way. Under 

 natural conditions it is usually the adjuvant micro-organisms that aid 

 the tetanus infection by hindering the phagocytes from seizing the 

 spores with sufficient rapidity to prevent their germination. This 

 fundamental result, established by Vaillard and Vincent, has often 

 been gainsaid on the evidence of insufficient experiments (Sanchez- 

 Toledo, Klipstein, Roncali), but, ultimately, its accuracy has been 

 completely confirmed. Cases have been cited in which the tetanus 

 spores, deprived of their toxin, still set up a fatal tetanus. When a 

 small fragment of an agar culture of tetanus, previously heated to 

 85 C. for the purpose of destroying the toxin, is inoculated, we 

 produce tetanus. Vaillard and Rouget have demonstrated that, under 

 these conditions, the leucocytes penetrate merely into the superficial 

 layer of the agar, the spores germinating and the bacilli multiplying 

 in the deeper part. We can also set up a fatal tetanus in animals 

 by inoculating, along with sterilised earth, spores deprived of their 

 toxin by means of heat The particles of soil protect the spores 

 against the aggression of the phagocytes, allow them to germinate 

 and then to poison the organism. Lactic acid produces an analogous 

 effect, by destroying or weakening the phagocytes. Micro-organisms, 

 most often inoffensive in themselves, also prevent the phagocytosis 

 of the tetanus spores and thus aid the intoxication. 

 ] The facts above summarised have been demonstrated to be the 

 rule for several species of anaerobic pathogenic bacteria. Thus, 

 Besson 1 showed that the septic vibrio is, by itself, incapable of setting 



1 Ann. de VInsl. Pasteur, Paris, 1895, t. ix, p. 179. 



