374 GLANDERS ANTHRAX PYOCYANEUS 



surface, where sporulation may occur. If these temperatures are 

 exceeded in either direction, spore formation does not occur. The 

 spores, which are oval, are situated at or near the centre of the cell 

 and measure about 0.8 micron in diameter and from 1.2 to 1.4 microns 

 in length. Occasional asporous strains 1 are met with, and spore 

 formation may be suppressed by cultivating the bacteria at 42 C. 

 for several hours or in fluid media containing potassium bichromate 

 in dilutions from 1 to 5000 to 1 to 2000, or small amounts of phenol. 2 

 Lehmann 3 states that long-continued transfer of cultures from gelatin 

 to gelatin frequently leads to a suppression of spore formation. Some 

 strains become asporeless much more readily than others. 4 Spores 



FIG. 53. Bacillus anthracis, showing capsule formation. X 1000. (Kolle and Hetsch.) 



are not formed in the intact animal body. Mature vegetative bacilli 

 emerge from the spores in the presence of oxygen, if the temperature 

 is maintained between 15 and 40 C. The spore membrane merges 

 imperceptibly into the newly formed vegetative cell; no visible rup- 

 turing of the spore membrane is detectable. 



Bacillus anthracis stains well with ordinary anilin dyes and young 

 cultures are Gram-positive. Older cultures may gradually lose their 

 ability to retain Gram's stain. Spores may be stained with the Ziehl- 

 Neelsen stain. (See Staining of Spores.) 



Isolation and Culture. Bacillus anthracis grows readily upon any 

 artificial media. Material is best obtained from the spleen or liver 



1 Asporous cultures do not necessarily become avirulent (Chamberland and Roux, 

 Compt. rend. Acad. des Sci., 1883, xcvi, 1090). 



2 Roux, Ann. Inst. Past., 1890, 25. 



3 Miinchen. med. Wchnschr., 1887, No. 26. 



4 Surmont and Arnould, Ann. Inst. Past., 1894, p. 832. 



