160 TECHNOLOGY OF BACTERIA. 



forms irregularly mixed together/' injected be- 

 neath the skin of the animal, gives rise to an 

 infective disease characterized by, and dependent 

 upon, the presence of a multitude of minute ba- 

 cilli in the blood and tissues. In this case, it is 

 evident that the conditions are favorable for the 

 multiplication of this species, and not for the 

 others associated with it in the drop of putrid 

 blood introduced into the living culture-apparatus. 

 This experiment enables us to secure a pure cul- 

 ture of this particular bacillus; for the smallest 

 quantity of blood taken from the vessels of the 

 animal, immediately after its death, contains it in 

 abundance, and may be used to inoculate a steril- 

 ized culture-fluid. In the same way, if we inocu- 

 late a rabbit with a drop of human saliva, which 

 contains a variety of bacteria, one species only 

 multiplies freely and invades the blood of the ani- 

 mal, producing a fatal infectious disease. This is 

 a micrococcus of oval form and having peculiar 

 characters. (Fig. 3, Plate IX.) By introducing a 

 little of the blood of a rabbit, just dead as the 

 result of such an inoculation, into a sterilized cul- 

 ture-fluid, we obtain a pure-culture of this micro- 

 coccus, which may be maintained indefinitely 

 through successive generations from culture-tube 

 to culture-tube, or from rabbit to rabbit, thus show- 

 ing that this micrococcus is a distinct species, as 

 it "breeds true." 



Having obtained pure stock by one of the 

 methods mentioned, success in cultivating the spe- 



