GENUS BACTERIUM 223 



it gradually undergoes granular degenration and loses its 

 staining capacity. 4 Oxygen is necessary for their formation 

 and they are consequently not found in the blood or tissue of 

 infected subjects. The spores are located in the middle of 

 the organisms and they are distinctly oval. In preparations 

 from animal tissues, especially the blood, a capsule is ob- 

 served surrounding the organism. This is never seen in 

 preparations from the ordinary culture medium. Its pres- 







Fig. 50. Anthrax bacteria in a cover-glass preparation of blood, 

 showing short chains and capsules. 



ence has been recorded by some observers when the organism 

 was cultivated in fluid blood serum. In blood from infected 

 animals the organisms frequently appear in short chains. In 

 these cases the capsule surrounds the entire chain. 



Staining. They stain readily with the usual aniline dyes 

 and with gentian violet and fuchsin in aqueous solution. The 

 spores are difficult to stain but may be demonstrated by any 

 of the usual methods for staining spores. The organisms re- 

 tain the stain when treated by the Gram method. A differen- 

 tial stain has been described by M'Fadyean 5 which he consid- 

 ers of much practical value. 



4 Behring. Zeit. f. Hyg., Bd. VI and VII, 1889; Deut. med. Woch., 

 1889. 



5 M'Fadyean. Jour. Conip. Path, and Therap., Vol. XVI (1903) 

 p. 35. 



