846 BACILLUS 



when B. anthracis is grown in a broth culture toxic albumoses are formed, 

 which prove fatal on injection into animals ; Martin also found a toxic alkaloid. 

 There is no evidence that a true exotoxin is formed ; the toxic substances appear 

 to be formed largely by the disintegration of the proteins in the medium. Aoki 

 and Yamamoto (1939) bring evidence to suggest that B. anthracis forms an endo- 

 toxin which is capable of activating spores in vivo. The formation of a haemolysin 

 has been asserted by some authors, and denied by others ; it is possible that 

 diiferent strains may vary in this respect. There is certainly no haemolysin pro- 

 duced for cattle or horse blood, but there is evidence to suggest that one may be 

 formed for sheep, goat and rabbit blood (Poppe 1922). 



The main criteria of value in the difierentiation of B. anthracis from those 

 bacilli which may be confused with it may be given in tabular form : 



B. anthracis. Anthrax-like or so-called pseudoanthrax bacilli. 



1. Non-motile. Generally motile. 



2. Capsulated. Non-capsulated. 



3. Grows in long chains. Grow in short chains. 



4. No turbidity in broth. Frequent turbidity in broth. 



5. Inverted fir-tree growth in gelatin. Fir-tree growth absent or atypical. 



6. Polysaccharide precipitin reaction Polysaccharide precipitin reaction 



strongly positive. weakly positive. 



7. Pathogenic to laboratory animals. Non-pathogenic to laboratory animals. 



8. Liquefaction of gelatin slow. Liquefaction of gelatin rapid. 



An inverted fir-tree growth in gelatin is given by some strains of pseudoanthrax 

 bacilli, but the branches are thick and interlaced, quite different from the regular, 

 delicate, lateral outgrowths of B. anthracis. It is sometimes stated that the 

 anthrax bacillus does not show haemolysis on blood agar plates, whereas the 

 pseudoanthrax bacilli form colonies surrounded by a zone of hsemolysis. This 

 depends on the type of blood used, and is at best an uncertain criterion for 

 differentiation. 



When freshly isolated from the animal body, the anthrax bacillus rarely causes 

 difficulty in identification, but after prolonged subculture in the laboratory it 

 may lose several of its important characteristics, such as capsule formation, the 

 inverted fir-tree growth in stab gelatin, and its pathogenicity for laboratory 

 animals, and may then be very difficult to classify. Nevertheless bacilli have 

 been described which have given rise to an anthrax-like disease in man and other 

 animals, yet which have not conformed to the usual criteria of B. anthracis 

 (Schulz 1901, Wilamowski 1912, Senge 1913). Such bacilli have usually been 

 classed as pseudoanthrax bacilli, but it is probable that some at least have been 

 variants of the real B. anthracis, similar to those described by Preisz (1911). 



The characters of certain species of Bacillus are summarized below. 



Bacillus anthracis 



Synonyms.- — Bacteridie du charbon, MilzbrandbaciUus. 



Habitat. — Parasitic in man, cattle, sheep and other animals. 



Morphology. — Rods, 3-8 ^ X 1-1*2 fi. Straight or slightly curved, ends truncate; on 

 agar plates arranged characteristically in very long, segmented, parallel, or inter- 

 woven chains. Unjointed filaments not infrequent in cultures. In blood of ani- 

 mals mostly in pairs or chains of 3 or 4. Spores equatorial, eUipsoidal, not bulging ; 

 polar germination ; not formed in animal body. Non-motile. Capsule found in 



