722 PATHOGENIC MICROORGANISMS 



ceases below 10 to 12 C. Kept at room temperature and protected 

 from drying, the bacillus may remain alive, in cultures, for several 

 months. 



The bacillus is not very fastidious as to reaction of media, grow- 

 ing equally well on moderately alkaline or acid media. It is aerobic 

 and facultatively anaerobic; growth under anaerobic conditions, 

 however, is not luxuriant. 



On agar, growth appears in the form of grayish-white mucus-like 

 colonies, having a characteristically slimy and semi-fluid appearance. 

 Colonies have a tendency to confluence, so that on plates, after three 

 or four days, a large part of the surface appears as if covered with 

 a film of glistening, sticky exudate, which, if fished, comes off in a 

 tenacious, stringy manner. It is often possible to make a tentative 

 diagnosis of the bacillus from the appearance of this growth. 



In broth, there is rapid and abundant growth, with the formation 

 of a pellicle, general clouding, and later the development of a pro- 

 fuse, stringy sediment. 



Stab cultures in gelatin show, at first, a white, thin line of growth 

 along the course of the puncture. Soon, however, rapid growth at 

 the top results in the formation of a grayish mucoid droplet on the 

 surface, which, enlarging, gives the growth a nail-like appearance. 

 This nail-shape was originally described by Friedlander and 

 regarded as diagnostic for the bacillus. The gelatin is not fluidified. 

 As the culture grows older the entire surface of the gelatin tube 

 may be covered with growth, flowing out from the edges of the 

 nail-head. The gelatin acquires a darker color and there may be 

 a few gas bubbles below the surface. Microscopically, colonies on 

 gelatin plates have a smooth outline and a finely granular or even 

 homogeneous consistency. 



On blood serum, a confluent mucus-like growth appears. 



On potato, abundant growth appears, slightly more brownish in 

 color than that on other media. 



In pepton solutions, there is no indol formation. 



In milk, there is abundant growth and marked capsule develop- 

 ment. Coagulation occurs irregularly. 



In considering the general cultural characteristics of the Fried- 

 lander bacillus, it must not be forgotten that we are dealing with a 

 rather heterogeneous group, the individuals of which are subject to 

 many minor variations. Capsule development, lack of motility, in- 

 ability to fluidify gelatin, failure to form indol, and absence of 



