76 AIDS TO BACTERIOLOGY 



surface, spikelets at once begin to radiate over this in 

 wavy convolutions, liquefying the gelatin. This stage is 

 usually reached in two days, and is most characteristic. 

 In the gelatin stab, growth takes place along the needle 

 track, fine branching filaments often growing out into 

 the gelatin (' inverted fir-tree growth '). Liquefaction 

 commences at the top of the stab, proceeding downwards 

 in a horizontal plane, upon which a mass of bacilli rest, 

 leaving the gelatin above clear and liquid. In broth a 

 flocculent growth forms at the bottom of the tube, the 

 bulk of the broth remaining clear and no pellicle forming. 

 On agar a thick, grey-white, sticky growth takes place, 

 and on potato a considerable white growth, both usually 

 containing a large number of spores. Blood-serum is 

 slowly liquefied. An alkaline reaction is generally favour- 

 able to the growth of this organism, although it grows well 

 on potatoes, which are normally acid The bacilli stain 

 well by Gram's method. 



Pathogenesis. In the human subject the disease 

 appears as (1) malignant pustule, a localised swelling 

 caused by direct inoculation, and (2) ivoolsorter* s disease, 

 a general infection caused through inhalation of spores 

 during the handling of wools, hides, and fleeces. Infec- 

 tion may also take place through the digestive organs 

 (intestinal anthrax). A single case of the lesion appearing 

 in the larynx is reported. In cattle the disease is known 

 as ' Siberian plague ' or ' splenic fever,' the latter cog- 

 nomen being due to the much swollen and soft condition 

 of the spleen found in infected animals. In man, enlarge- 

 ment of the spleen is less marked, and the disease appears 

 to take the form of a toxaemia. 



It is pathogenic to the following animals, which are 

 arranged roughly in order of their susceptibility: mice, 

 guinea-pigs, rabbits, sheep, cattle, horses, man, goats, and 

 pigs. Algerian sheep, dogs, frogs,* and white rats are 

 immune. 



In susceptible rodents there may be considerable in- 

 flammation around the seat of inoculation, and the sub- 

 cutaneous connective tissue may be distended with a 

 bloody gelatinous exudation. If the tissue is examined 

 microscopically, the blood is found to be full of bacilli, 



* Unless the frog is warmed to 37 C. 



