110 SPECIAL BACTERIOLOGY 



sections of organs stained by the Gram or Cladius methods they are 

 easily demonstrated (see Photomicrograph, Plate I., Fig. .3), showing a 

 section of a mouse's lung with the capillaries filled with bacilli. 



On artificial media the bacilli grow in long, parallel, or somewhat 

 twisted and interlaced threads, which either form spores or degenerate 

 into the so-called involution forms (see Photomicrograph, Fig. 37). 



Motility. Non-motile. 



Staining Reactions. The bacilli stain easily with all the ordinary 

 aniline dyes, with haematoxylin, and by the Gram and Cladius methods. 



Spore Formation. The bacilli form spores under aerobic conditions 

 at a temperature of 15 to as high as 37 C. Giinther considers 28 C. 

 the optimum, and that at a higher temperature the formation is some- 

 what irregular. 



Spores are never formed in the living animal or in unopened carcases. The 

 latter is most important from a sanitary point of view, in regard to the 

 disposal of the carcases of animals dead from anthrax. The spores are 

 ovoid, and one to two times as long as broad, one spore being present in 

 nearly every bacillus, giving the thread the appearance of a chain of 

 beads (see Photomicrograph, Plate I., Fig. 2). For the special method 

 of staining the spores of the Bacillus anthracis, see Technique, 27. 



Vitality. The resistance of anthrax spores to outside influences is 

 not always constant. Some spores are killed by exposure to 5 per cent, 

 carbolic acid in two days, and to steam at 100 C. in three minutes, 

 while others resist 5 per cent, carbolic acid over forty days, and steam at 

 100 C. for more than twelve minutes. In a dry state the spores are 

 destroyed instantly at 160 C. 



When the bacilli are cultivated in bouillon to which ^JL^ to T J Qn 

 bichromate of potash is added, they lose the faculty of forming spores 

 without losing their virulence. The power of forming spores is also lost 

 when the bacilli are cultivated for many generations on gelatine media. 



Biological Characters. The Bacillus anthracis is a facultative 

 aerobic organism growing best in the presence of oxygen, and in its 

 absence slowly without liquefying the media. Exhibits no growth in 

 CO,,. It grows quickly at 37 C., and ceases to grow under 12 and above 

 45 C. 



On Gelatine Plates. On the surface small whitish colonies appear, 

 while those deeper in the medium are of a greenish-black colour. Under 

 a low power the colonies exhibit a characteristic tangled mass of single 

 threads projecting beyond the edges of the colonies in curly hairy tufts. 

 The colonies begin to liquefy in three or four days. 



In Gelatine Stab Cultures. In twelve to twenty hours a thick, white 

 central thread appears, from which white threads and branching rootlets 

 radiate (see Photo., Fig. 36). After two days, liquefaction commences on 



