324 MANUAL OF BACTERIOLOGY. 



of a 20 per cent, peptone solution to make the water contain 

 I per cent, peptone, and enough of a 10 per cent, sodium chloride 

 solution to make 5 per cent. The water, with the salt and 

 peptone in it, is divided among a number of sterihzed flasks. 

 After twelve hours in the incubator, any cholera spirilla which 

 happen to be present are likely to multiply and form a scum 

 on the surface of the medium, and may be identified according 

 to the methods given above. See also page 131. 



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, hke 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 ahke; 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 pel- 

 hcle on bouillon. In milk an acid reaction is developed with 

 coagulation. In peptone solution it produces indol and ni- 

 trates like the spirillum of cholera. It is said to give the nitro- 

 soindol reaction more intensely than the spirillum of cholera. 



It is killed by a temperature of 50° C. in five minutes. It 

 was discovered in chickens suffering from gastro-enteritis. 



