THE BIOLOGICAL CHARACTERS, ETC. 33 



the same observation, and since that time this behaviour has 

 been held as differential, since Eberth's bacillus causes such 

 a medium to become uniformly turbid in twenty-four hours, 

 but after a few days the medium clears and no development 

 of gases takes place. The fermentation of sugar by bac- 

 terium coli commune is stated by Dunbar to yield gas after 

 three hours' incubation at 3/°C, and by the end of the fourth 

 day an amount of gas is produced which amounts to about 

 one-third of the volume of the culture medium ; this gas 

 consists of carbon dioxide and hydrogen. The new gas- 

 forming bacillus described quite recently by Gartner (25) 

 from . the peritoneal cavity is, according to Klein (26), 

 identical with bacterium coli commune and probably reached 

 this situation by direct migration from the gut. The so- 

 called indol reaction described by Kitasato (27) consists in 

 the addition of 1 ccm. of '02 solution of potassium nitrite 

 with a few drops of concentrated sulphuric acid to 10 ccm. 

 of a bouillon culture. If this is a pure growth of bacillus 

 typhosus the characteristic red colour seen with cultures of 

 Escherich's bacillus and other typhosus-like bacteria is 

 absent. A reaction described by Zinno (28) and dependent 

 upon the presence of kreatinine is performed by adding a 

 few drops of sodium carbonate and very dilute solution of 

 nitro-prusside of sodium to suspected growths in two per 

 cent, peptone bouillon. An intense red colour develops 

 which gradually fades into yellow. By the addition of 

 acetic acid an emerald green colour appears which passes 

 into blue. These reactions are given by cultures of 

 bacterium coli from many sources but not by bacillus 

 typhosus. Cultures of Koch's spirillum and vibrio Metchni- 

 kovi respond to the above tests, which is not the case with 

 the spirillum of Deneke or that of Finkler-Prior. 



The behaviour of the typhoid bacillus and allied organ- 

 isms when cultivated upon sterile milk was first noted by 

 Chantemesse and Widal (29), who established the fact, which 

 has been verified by all subsequent observers, that the bacil- 

 lus typhosus does not cause coagulation of milk, while this 

 is a constant feature in the growth of bacterium coli com- 

 mune. In connection with this Eberth's bacillus, though it 



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