4i8 MICRO-ORGANISMS AND DISEASE [chap. 



noticed in the culture-tube ; with a platinum loop a droplet 

 is taken from the superficial layers of the culture fluid and 

 examined in the living state (hanging drop) or in stained 

 film specimens. In the former the individual commas and 

 the characteristic S-shaped forms can be easily recognised 

 under the microscope both by their shape and by the 

 peculiar corkscrewlike movement ; in the stained film speci- 

 men the presence of commas and particularly of S-shaped 

 forms is of importance. 



From these peptone cultures subcultures in Agar plates 

 (at 37° C.) or in nutrient gelatine plates are then made for 

 further isolation, and if the peptone culture on micro- 

 scopic examination (stained film specimen) be found fairly 

 pure the addition of a few drops of pure sulphuric acid to 

 the peptone culture produces the nitroso-indol reaction of 

 Bujwid^ and Dunham 2, ix. a pink colouration of the cul- 

 ture — cholera-red reaction. If the cholera vibrios are, 

 however, mixed with other bacteria (bac. coli or proteus) 

 then they must be first purified by plate cultures, and from 

 the colonies of cholera vibrios of these plates pure peptone 

 cultures can be made for the Bujwid-Dunham test. 



Loffler, as has already been stated in a former chapter, was 

 the first to stain the flagella of the cholera vibrios, and he 

 found that each comma bacillus possesses one spiral flagellum 

 at one end ; but it can be shown by van Ermengem's modifica- 

 tion that, though this is the rule, occasionally more than one 

 such flagellum is present. I have shown ^ that by staining 

 the flakes of a typical rice-water (cholera) stool with gentian 

 violet the flagella of the cholera vibrios can be demonstrated 

 as stained wavy or spiral appendages, and in some cases I 



' Zeitschrift f. Hygiene, vol. ii. I, p. 52- 



^ Ibid., vol. ii. 2, p. 337. 



' Qentralbl. f. Bakteriol. mid Parasil., vol. xiv. No. 15. 



