244 BACTERIA IN INFECTIOUS DISEASES. 



be able to support the development of the microbe, 

 although with less energy than at the outset. \Ve 

 comprehend, then, that after a cultivation of the modi- 

 fied (attenue) microbe in the body of the fowl, we may 

 not have removed from all parts of its body the aliment 

 of the microbe. That which remains will permit, then, 

 a new culture, but in a more restricted measure. 



** This is the effect of a first inoculation ; subsequent 

 inoculations will remove progressively all the material 

 necessary for the development of the parasite. 



" Is this the only possible explanation of the phenom- 

 enon ? No ; we may admit the possibility that the 

 development of the microbe, in place of removing or 

 destroying certain matters in the bodies of the fowls, 

 adds, on the contrary, something which is an obstacle to 

 the future development of this microbe. The history 

 of the life of inferior beings authorizes such a supposi- 

 tion. The excretions resulting from vital processes 

 may arrest vital processes of the same nature. In cer- 

 tain fermentations we see antiseptic products make 

 their appearance during, and as a result of, the fermen- 

 tation, which put an end to the active life of the fer- 

 ments, and arrest the fermentations long before they 

 are completed. In the cultivation of our microbe, pro- 

 ducts may have been formed the presence of which, 

 possibly, may explain the protection following inocula- 

 tion. 



" Our artificial cultures permit us to test the truth of 

 this hypothesis. Let us prepare an artificial culture 

 of the microbe, and after having evaporated it, in vacuo, 

 without heat, let us bring it back to its original volume 

 by means of fresh chicken bouillon. If the extract con- 

 tains a poison for the life of the microbe, and if this is 

 the cause of its failure to multiply in the filtered 

 liquid, the new liquid should remain sterile. Now this 



