402 CLINICAL BACTERIOLOGY. 



which it gives rise in all nutrient media. In gelatin stab- 

 cultures a nail-shaped growth develops at first, the head subse- 

 quently extending. 



5. Bacillus Rubefaciens, This is a fine rod, consisting of 

 two or more segments. Gelatin-cultures exhibit a pale rose-red 

 color. Upon potatoes the substratum appears of a rose-red 

 color, while the colony itself is between yellowish-gray and 

 brownish-red. 



6. Bacillus Subflavus. Cultures of this organism give rise 

 to a pale-red pigment; upon plates they exhibit a mother-of- 

 pearl luster. The pigmentation is most distinct in agar-agar 

 cultures. Several bacilli often lie attached to one another. 

 The individual organism is from two to four times as long as 

 it is thick. 



7. Bacillus Brunneus. The colonies of this small, nonmotile 

 bacterium are characterized by diffusing a brownish pigment into 

 the surrounding culture-medium. 



(b) Nonchromogenic. 



8. Typhoid-like, Bacilli (Weichselbaum). Under this desig- 

 nation is included a group of motile bacilli that resemble 

 the bacillus of Eberth-Gaffky and the bacterium coli commune 

 in both morphologic and cultural properties. On plates the 

 colonies present easily the appearances of those of the typhoid- 

 bacillus and the colon-bacillus (pp. 167, 120). Upon potatoes 

 a deposit forms, at times brownish, at other times yellowish, at 

 still other times scarcely visible. Coagulation is induced in 

 milk. Some varieties cause fermentation of grape-sugar, while 

 others do not. The nitroso-indol reaction is positive with some, 

 and negative with others. These bacteria are free from all 

 pathogenic activity in experiments on animals. That this group 

 is constituted of a series of bacteria differing among themselves 

 is demonstrated by the fact that any one variety is incapable of 

 conferring immunity to any other. The attempt, also, to cause 

 agglutination in the cultures of one variety with the blood- 

 serum of animals that have been immunized to another variety 

 has invariably failed. 



2. LIQUEFYING GELATIN. 



(a) Chromogenic. 1 



p. Bacillus Arborescens. This is a slender bacillus that fre- 

 quently forms wavy filaments. It is incapable of spontaneous 

 movement, and it is characterized by branch-like ramifications in 

 gelatin plate-cultures, and by iridescence of its colonies. It 

 gives rise to a yellowish or yellowish-red pigment, especially 

 upon potatoes. 



10. Bacillus Fluorescens Liquefaciens : This is a motile 



