YII5RIU MKTSrilNlKnFFI 147 



its speedier liquefaction on the gelatine plate, and the 

 yellowish colour of the colonies, which appear irregular 

 under the microscope, and are surrounded by a thick ram- 

 part. Like the cholera bacillus, it shows an air-bubble in 

 thrust-cultures at the uppermost part of the funnel-shaped 

 excavation, but the bubble is larger than in the former case 

 (fig. 53). A delicate yellowish coat, composed of beautifully- 

 formed spirilla, appears on potatoes at incubation tempera- 

 ture. Like the VU>rn> j>n>t,'ns, this bacterium possesses 

 pathogenic properties. 



The differential diagnosis of the Bacillnx nrdjioHttiniia 

 (p. 120), regarded by Emmerich as the originator of 

 cholera, presents no difficulties, as its elements are short 

 immotile rods and the gelatine is not liquefied by their growth, 

 which takes place more chiefly upon its surface. 



The Vibrio Metschnikoffi, which was found by Gamaleia 

 in the intestinal contents in a Eussian disease of poultry, is 

 a curved bacterium forming screw-shaped spirilla of con- 

 siderable length, but which is shorter and thicker than the 

 cholera bacillus. Its accurate identification is often difficult, 

 as, although the gelatine of plate-cultures becomes fluid 

 at times as rapidly as with Vibrio j>r<>f<'iis, the liquefaction is 

 sometimes greatly protracted. The thrust-culture shows a 

 distinct air-bubble, which gradually enlarges, and disappears 

 when liquefaction is complete. It grows on potato as a 

 brown deposit, but only at the temperature of the incubator. 



A peculiarly characteristic property of the cholera 

 bacillus lies in the cholera reaction already alluded to, which 

 was discovered by Bujwid and Dunham. Cultures of the 

 bacilli in media containing peptone (bouillon or gelatine) 

 give a reddish-violet or purple-red colour in a short time 

 when treated with pure hydrochloric or sulphuric acid, in 

 which process a definite pigment, cholera red, is developed. 

 Salkowski explains this as an indol reaction, since that sub- 



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