CHAPTER IX. 



STUDY AND IDENTIFICATION OF BACTERIA. SPIRILLA. 

 KEY AND NOTES. 



KEY to recognition of gelatin liquefying, motile and Gram negative 

 spiral or comma-shaped organisms. 



A. Do not give the nitroso-indol reaction with sulphuric acid alone in twenty-four 

 hours. 



1. Produce an abundant moist cream-colored growth on potato at room tempera- 

 ture. 



a. Finkler and Prior's spirillum (Vibrio proteus). Liquefaction of gelatin 

 very rapid. No air-bubble appearance at top of liquefied area. Cultures 

 have foul odor. Milk coagulated. Thicker spirillum than cholera. Iso- 

 lated from cholera nostras. 



2. Scanty growth or none at all on potato at room temperature. Only a mod- 



erate yellowish growth when incubated about incubator temperature, 

 a. Spirillum tyrogenum (Deneke's spirillum). Does not liquefy gelatin so 

 rapidly as Finkler Prior. Thinner and smaller spirillum than cholera. 



B. Give the nitroso-indol reaction with sulphuric acid within twenty-four hours. 



1. Very pathogenic for pigeons. 



a. Spirillum metschnikovi. Liquefies gelatin about twice as rapidly as 

 cholera. Gives bubble appearance at top of stab. 



2. Scarcely pathogenic for pigeons, 

 a. Spirillum choleras asiaticae. 



Nonmotile, nonliquefying and Gram positive spirilla have also been described. 

 There is also a large group of phosphorescent spirilla. 



Spirillum cholerae asiaticse (Koch, 1884). Typically, the mor- 

 phology of this organism is that of the comma (Comma bacillus of 

 Koch). It also frequently shows S shapes, and often appears in long 

 threads showing turns. When freshly isolated from cholera material 

 they, as a rule, show a fairly typical morphology, but after subcultures 

 in the laboratory variations are common, so that rod forms and round 

 involution shapes give a picture altogether at variance with the comma 

 shape. 



Even in recent cultures of undoubted cholera we may have different types, as 

 coccoid forms and slender rods. Ohno has noted the fact that the same strain of 

 cholera will give at one time vibrio forms and again coccoid or rod forms, depending 



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