2 QO BACTERIOLOGY. 



bacilli of their virulence. The virulence of the 

 bacillus is also altered by passing the bacillus 

 through different species of animals. The bacillus 

 of sheep or cattle is fatal when re-inoculated into 

 sheep or cattle ; but, if inoculated in mice, the 

 bacilli then obtained lose their virulence for sheep 

 or cattle ; only a transitory illness results, and the 

 animals are protected for a time against virulent 

 anthrax.* The possibility of mitigating the virus 



KIG. no. SPORES OF BACILLUS ANTHRACIS UNSTAINED, x 1500. 



depends upon the species of animal ; rodents cannot 

 be rendered immune by any known " vaccin." 



METHODS OF STAINING THE BACILLUS ANTHRACIS. 



Cover-glass preparations of blood, etc., can be stained 

 with a watery solution of any of the aniline dyes. They 

 may be rapidly stained with a drop of fuchsine or gentian 

 violet (p. 48), but more satisfactorily by floating the cover- 

 glasses for twenty-four hours. The preparations may be 

 dried and mounted in Canada balsam, but the typical 

 appearances are best observed in freshly-stained specimens 

 examined in water. 



The sheath and protoplasmic contents can be differen- 

 tiated by staining with eosin after the method of Gram. 



* Klein, Reports of the Medical Officer of the Local Government 

 Board. 1882. 



