200 MICROBES AND TOXINS 



assume that the action goes on in the interior of the 

 phagocytes. 



To refute the old opinion that the leucocytes form a good cul- 

 ture medium for bacteria and serve as convenient vehicles for 

 them, it has been necessary to show that in the phagocytes the 

 bacteria die and are digested. To refute the opinion that the 

 phagocytes simply incorporate bacteria already damaged or 

 killed by other (humoral) actions, it has been necessary to 

 show that bacteria are ingested in a living and virulent condition : 

 as a matter of fact living motile bacilli (B. pyocyaneus} can be 

 seen in the interior of a frog's leucocyte. Fatal anthrax can be 

 produced in a guinea-pig by inoculating anthrax bacilli already 

 engulfed by the phagocytes of a frog : it is only necessary not 

 to wait too long, or digestion in the leucocyte may be completed. 

 Pasteur noted that it was perfectly easy to kill the fowl and the 

 rabbit by inoculating them with bacilli of fowl cholera already 

 incorporated by the leucocytes of the refractory guinea-pig. 

 The bacteria attacked by the phagocytes are therefore 

 thoroughly alive and virulent. 



If we take an animal immunised against vibrios and inocu- 

 late it with the same microbes against which it is immune ; if 

 we withdraw now a drop of the exudate provoked by the 

 inoculation and make of it a hanging drop in a sealed chamber 

 at incubator temperature, we find that the phagocytes thus 

 withdrawn from the body promptly die and the bacteria grow 

 in their interior as if in culture. But from the phagocytes 

 withdrawn from the animal a little later no such culture can be 

 obtained ; the phagocytes have had time to digest the bacteria. 

 No better conception can be furnished than this of the life and 

 death of bacteria in the phagocytes. 



It has been said that the body-fluids have already attenuated 

 the virulence of the microbe before its capture by the phagocyte. 

 If such previous attenuation exists their remains still to be settled 

 whether it is due to a cellular or to a humoral action : in any 

 case it is far from being the rule. In Charrin and Roger's 

 experiments the streptococcus, the pneumococcus, and the 

 pyocyaneus bacillus grown in the serum of an immunized 



