KEY TO GENUS BACTERIUM. 197 



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

 Eberth, page 232. 



(/3) 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. cholerae suum, 

 L. and N. , page 252. 



(y) 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. 



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

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

 page 243. 

 (C) Gelatin not liquefied. Forms acetic acid , from alcohol. 

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

 bacteria. 

 (Z>) 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. 



(/?) 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. caniculae (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. 

 (/?) 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. fcetidum liquefaciens, cloacae, agile, page 265. 



