482 INFECTION AND IMMUNITY. 



the atypical forms. In bouillon long chains de- 

 velop. It is non-motile, has no flagella and forms 

 no spores. A capsule may be demonstrated by ap- 

 propriate technic. It does not stain by Gram's 

 method, and with methylene blue, carbol fuchsin, 

 etc., the ends stain more densely than the central 

 portion (polar staining). Because of its general 

 properties it is placed in a group with a number of 

 bacteria which cause hemorrhagic septicemias in 

 various animals the hemorrhagic septicemia 

 group." 



There occurs in bouillon the so-called stalactite 

 growth, in which visible processes extend from the 

 surface toward the bottom, where they meet other 

 processes which extend toward the surface "stalag- 

 mites"). These formations utilize as their starting 

 points the side of the flask or drops of butter or 

 oil which are placed on the surface. Certain other 

 organisms grow in a similar manner. It is said 

 to be a characteristic feature of the plague bacilli 

 that many involution forms appear on agar which 

 contains 3 per cent, of sodium chlorid. The opti- 

 mum temperature for growth is from 25 to 30 

 C., which is somewhat lower than that for most 

 pathogenic organisms. It grows rather slowly even 

 under the best conditions. In mixed cultures it is 

 overgrown by saprophytic organisms (e. g., colon 

 bacillus). 



viability The plague bacillus may live for from four to 

 Resistance, seven days in the putrefying organs of man or ani- 

 mals. Its virulence may be retained in the cadaver 

 of a rat for two months (Bandi and Stagnitta- 

 Balistreri). During this time the organisms pene- 

 trate all the tissues of the body, even growing 

 through the skin. It may live in the pus of a 



