KEY TO GENUS BACTERIUM. 197 



coagulated. No indol formation. Bact. typhi, 1 Gaffky, 

 Eberth, page 232. 



(ft) Fermentation of grape-sugar with formation of gas. Milk- 

 sugar affected only slightly or not at all and without forma- 

 tion of gas. Milk not coagulated. Bact. cholerse suum, 

 L. and N., page 252. 



(7) Fermentation of grape-sugar with formation of gas, milk- 

 sugar scarcely at all affected. In growth it is between the 

 Bact. typhi and Bact. coli. Bact. icteroides (Sanarelli), 

 L. and N., page 256. 



(6) Fermentation of grape- and milk-sugar with formation of 

 gas. Milk coagulated. Bact. coli (Escherich), L. and N., 

 page 243. 



(CO Gelatin not liquefied. Forms acetic acid from alcohol. 

 More details in tables, pages 261 and 262. Acetic acid 

 bacteria. 



(D) Gelatin liquefied, or consumed without visible liquefaction. 

 Organisms non-motile. 



(a) Gelatin liquefied in a funnel form. Sugar fermented. 

 Abundant growth on potato. Optimum temperature about 

 25. Agar is colored reddish-brown. Bact. discifor- 

 mans (Zimm.), L. and N., page 263. 



((3) Gelatin consumed in a funnel form without perceptible 

 liquefaction. No growth on potato. Optimum tempera- 

 ture 12. Agar not colored. Bact. salmonicida (Em- 

 merich and Weibel), L. and N., page 266. 



(E) Gelatin not liquefied, only slowly drawn in. Spontaneously 

 motile from polar flagellum. Stains by Gram's method. 

 Milk unchanged. Bact. caniculse (Galli-Valerio), L. and 

 N., page 260. 



(F) Gelatin liquefied. Organisms motile. 



(a) Grape-sugar fermented. No branches sent out toward the 

 solid gelatin. Bact. punctatum (Zimm. 2 ), L. and N., 

 page 264. 



()3) Grape-sugar fermented. Branches sent out toward the solid 

 gelatin. Bact. vitulinum (Weissenberg), L. and N., page 

 264. 



II. Formation of a yellow (greenish-yellow to orange-yellow) pigment 

 in the cultures of the bacteria upon agar and gelatin. ( Without fluores- 

 cent discoloration of the nutrient substratum. ) 



(A) Very small, thin, short rods ; upon gelatin and agar grow 

 slowly as a thin, intensely yellowish-green layer. Gelatin 

 very slowly liquefied. Possess a single flagellum. Bact. 

 turcosum (Zimm.), L. and N., page 267. 



(B) Short rods of the dimensions of the Bact. coli. 

 (a) Without spontaneous movement. 



1. Gelatin not liquefied. 



1 Compare Bact. typhi murium, page 258, and Bact. alcaligenes, 

 page 257. 



2 Compare also Bact. foetidum liquefaciens, cloacae, agile, page 265. 



