180 Chapter VTI 



ingestion of living flagellated Infusoria by the leucocytes of refractory 

 animals. 



These facts, fairly numerous in themselves, are not, hovrever, the 

 only ones that might be cited in favour of the fundamental thesis that 

 phagocytes possess all the means for incorporating living micro- 

 organisms. In my first works on phagocytosis I cited the example of 

 amoeboid cells, in the Invertebrata, containing motile bacteria ^ and 

 that of leucocytes of the frog charged with motile bacilli ^ of an 

 artificial septicaemia. Since then the number of similar cases has 

 increased considerably. Nothing is easier than to observe the phago- 

 cytosis of living micro-organisms in vitro. Take a drop of frog's lymph 

 and add to it a few of the Bacilli pyocyanei, we soon observe the 

 struggle between the leucocytes and the very motile bacteria, and 

 inside the digestive vacuoles bacilli executing very pronounced and 

 active movements. 



The same result may be obtained by another method, by which at 

 the same time we gather information as to the virulence of the micro- 

 organisms ingested by the phagocytes. The view has often been 

 expressed that phagocytes seize only those bacteria that have been 

 deprived of their virulence by a previous action of the fluids of 

 the animal organism ; consequently search has been made for some 

 attenuating property of these fluids. We have already answered this 

 objection in the previous chapter by the citation of cases in which 

 the exudations of refractory animals, containing only micro-organisms 

 ingested by the phagocytes, were, nevertheless, very virulent for sus- 

 ceptible animals. This question has been especially discussed in 

 relation to the anthrax of frogs, on which subject several investigations 

 have been carried out, the result of which is completely convincing. 

 Bacilli ingested by the leucocytes of these Batrachians retain their 

 full virulence for a long time. Exudations which contain only iutra- 

 [191] phagocytic bacilli, the majority of which have already lost their normal 

 staining by aniline dyes, produce fatal anthrax in susceptible animals, 

 such as the mouse and the guinea-pig. Mesnil has demonstrated 

 the same fact by using the exudations of fresh-water fishes that are 

 refractory to anthrax. The same rule applies equally to the exuda- 

 tions of dogs and fowls that have been inoculated with the bacillus. 



Long before these experiments on anthrax were made, Pasteur^ 



^ Arh. a. d. zool. Inst. d. Univ. Wien, 1883, torn, v, S. 160. 

 2 Biol. Centralbl., Erlangen, 1883-4, Bd. iii, S. 562. 

 ^ Compt. rend. Acad. d. sc, Paris, 1880, t. xc, p. 952. 



