400 MANUAL OF BACTERIOLOGY. 



flask, and put in the incubator at 37° C. and examined in from 

 8 to 18 hours. The examination consists in the microscopic 

 examination of the scum which forms more or less on the top 

 of the fluid — the flask showing the most scum is selected — 

 and in the application of the various tests for the identification 

 of the organism given above. See also page 145. 



Since Koch's discovery of the cholera spirillum in 1883-84 

 a considerable number of bacteria have been described which 

 resemble the cholera spirillum more or less closely, and these 

 have to be taken into account in making examinations of 

 suspected material of any sort. This is particularly necessary 

 in the investigation of water, in which such cholera-like spirilla 

 seem to occur quite frequently. 



Vibrio Metchnikovii. — A comma-shaped organism, which, 

 though somewhat shorter and thicker than the cholera bacillus, 

 is very similar to the latter in form, and, like this, may some- 

 times form genuine spirilla. It is motile and has a flagellum 

 at one end. It does not form spores. It is aerobic. It stains 

 with the aniline dyes, and is not stained by Gram's method. 

 It grows at the room-temperature. It liquefies gelatin some- 

 what more rapidly than the spirillum of cholera. The colonies 

 on gelatin plates are not all alike; some of them resemble 

 those of Vibrio proteus, and others are extremely like those of 

 the spirillum of cholera. It grows upon the usual media. 

 Coagulated blood-serum is liquefied by it. The growth on 

 agar is grayish to yellowish, and abundant. It forms a pellicle 

 on bouillon. In milk an acid reaction is developed with coagu- 

 lation. In peptone solution it produces indol and nitrates like 

 the spirillum of cholera. It is said to give the nitrosoindol 

 reaction more intensely than the spirillum of cholera. 



It was discovered in chickens suffering from gastro-enteritis. 

 It is pathogenic for chickens, pigeons and guinea-pigs; less so 

 for mice and not at all for rabbits.* The comma-shaped 



*Gunther. Loc. cit. p. 683. 



