246 IMPORTANT VARIETIES OF FISSION-FVNQL 



Agar Streak and Stab. — Like Bact. typhi, often more 

 luxuriant (18, in, iv, v). 



Bouillon Culture. — Cloudy, with a moderate, slimy 

 precipitate, which upon shaking rises up and becomes 

 homogeneously distributed. Sometimes there is a distinct 

 pellicle formed on the surface of the bouillon. 



Milk Culture. — Milk is usually rapidly coagulated; 

 more rarely, slowly. In connection with the ability to 

 break up milk-sugar, coagulation of milk is never al 

 Regarding non-coagulating forms, see under Bact. cholera; 

 suum. 



Potato Culture. — Growth with a wavy outline, at first 

 yellowish-white to grayish-yellow, later pea-yellow to yel- 

 lowish-brown and grayish-brown, partly flat, partly much 

 elevated, usually with a moist luster, less often dry and 

 dull. The potato in the region of the growth is usually 

 discolored (18, ix). Rarely the Bact. coli produ 

 delicate, almost invisible potato growth resembling that of 

 Bact. typhi. 



Resistance to various injuries is about like that of the 

 Bact. typhi. It is even more resistant to acids, formalin, 

 and other chemicals. According to Walliczeck, it bears 

 drying poorly (C. B. xv, 947). 



Chemical Activities. — 



(a) Chromogenesis : Only upon potato and always mod- 

 erate (yellowish-brown). 



(6) Odoriferous and gustable substances : Uncharacteristic, 

 ill-smelling substances are developed upon agar and gelatin, 

 but especially upon potato cultures. 



(c) Gas and acid production from carbohydrates : Grape- 

 and milk-sugar are fermented, with the production of a 

 mixture of acetic, formic, and lactic acids. According to 

 Oppenheimer, there are formed 70% volatile and 30% non- 

 volatile acids, and some iodoform-forming substance (alco- 

 hol). Many cultures ferment cane-sugar also. With this 

 fermentation there occur abundant C0 2 and H 2 in varying 

 proportion; we found about one-fourth CO,, the rest being 

 H and some N, but no marsh-gas. According to Pere (A. 

 P., 1893, 737), three different Bact. coli formed levorota- 

 tory lactic acid from nutrient media with grape-sugar, 

 which contained peptone as a source for nitrogen, just as 



