120 CLINICAL BACTERIOLOGY. 



lander is rod-shaped. It is arranged in pairs and in chains. 



(Fig. 42.) It also possesses a capsule, which is distinct, 



except in cultures. It does not stain by Gram's method. 



The bacillus grows vigorously as well at room-tempera- 

 ture as at the temperature of the 

 body. Upon gelatin-plates it forms 

 sma ^> porcelain-like points. The gela- 



^ n * s not nc i ue fi e d> k ut m tne c urse 



^ time is disc l re d brown. A stab- 

 culture assumes a typical nail-shape ; 

 an agar streak-culture, a thick succu- 



Fig. 42. Bacillus pneu- , T , , 



monke of Friediander. lent layer. In an agar stab-culture 

 gas is generated. Potato exhibits a 



yellowish coating and gas-formation. Grape-sugar nutrient 

 solutions undergo fermentation, with the formation of car- 

 bon dioxid, hydrogen, ethylic alcohol, and acetic acid. 

 Milk is not coagulated. Friedlander's bacillus retains its 

 power of development for a long time. 



Bacillus Pyocyaneus. The bacilli of green or blue 

 pus are small, slender, exceedingly active motile rods (with 

 a single flagellum) that in culture sometimes arrange them- 

 selves in small chains. They do not stain by Gram's 

 method. They grow almost as well at room-temperature 

 as in the thermostat. They exhibit facultative anaerobiosis, 

 but no spore-formation. On gelatin-plates flat, irregularly 

 circumscribed colonies form, with a radiate arrangement, 

 about which a zone of liquefaction soon forms. In gelatin 

 stab-culture liquefaction takes place rapidly. Upon agar 

 and potatoes there is vigorous development. Bouillon is 

 rendered densely turbid. Milk is coagulated and pepton- 

 ized. All cultures, especially, however, those containing 

 grape-sugar, soon assume a green or a greenish-blue color 

 that is imparted to the entire nutrient medium. The bacil- 

 lus pyocyaneus generates various pigments, according to 

 the constitution of the culture-medium, but only with free 

 access of oxygen. The best known of these is pyocyanin, 

 a crystallizable aromatic combination, related to anthracene 

 (Ledderhose), and a fluorescent green pigment. 



Bacterium Coli Commune. This appears as short, 

 narrow rods, frequently with vacuoles, twice as long as 

 wide, arranged in pairs. (Fig. 43.) Besides this simple form, 

 there is, however, marked pleomorphism, with long rods, 

 coccus-like bodies, and filaments. Motility is generally quite 



