66 STUDY AND IDENTIFICATION OF BACTERIA 



The bacillus is 5 to 8/* by i to i i/2//. It has square cut or concave 

 ends and is often found in chains. It is Gram positive. Colonies, by 

 interlacing waves of strings of bacteria, show Medusa head appearance. 

 For cultural characteristics see key. Spores develop best at a tempera- 

 ture of 30 C. They stain with difficulty. 



Stiles thinks that animals are infected by eating the bones of animals which have 

 died of anthrax, cutting buccal mucous membrane, and so becoming infected. 

 Spores do not form in an intact animal body, but they do form after a postmortem 

 or the disintegration of the body by maggots. For this reason it is better not to 

 open up the body of the animal, but to make the diagnosis by cutting off an ear. 

 Dried spores will live for years and will withstand boiling temperature for hours. 



In vaccinating animals against anthrax, Pasteur used two vaccines. The first 

 is attenuated fifteen days at 42.5 C. The second, attenuated for only ten days, is 

 given twelve days later. 



FIG. 18. Bacillus anthracis in blood of rabbit. (Coplin.} 



In taking material from a malignant pustule before excision, be 

 careful not to manipulate it roughly, as bacteria may enter the circula- 

 tion. Make cover-glass preparations, staining by Gram. Make 

 culture on agar. Blood cultures are usually only positive later in the 

 disease. Inoculate a guinea-pig or a mouse subcutaneously. 



The guinea-pig dies in about forty-eight hours and shows an cedematous gelatin- 

 ous exudate at site of inoculation. The blood is black and swarms with anthrax 

 bacilli. It is the best example of a septicaemia. 



An organism with a central spore and morphologically resembling 

 B. anthracis, but motile, has been reported as occurring in the stools 

 of pellagrins. Gelatine stabs show a cup-shaped liquefaction in about 



