BACTERIUM COLL 245 



acid than it can tolerate, and so dies out. It grows well 

 in nutrient media which contain no albumin. 



Remarks Regarding the Macroscopic Growth of 

 the Bact. coli. All closely observing recent authors 

 (Dunbar, Ferrati, Losener, etc.) state that the Bact. typhi 

 and Bact. coli cannot be differentiated with certainty by 

 means of their cultures, but only that generally the coli 

 bacteria grow more luxuriantly upon the various nutrient 

 media. The color is white, often, in thick growths, be- 

 coming gray or yellowish-white. 



Gelatin Plate. (a) Natural size: Like the Bact. typhi, 

 except that here the moist, opaque forms (not uncom- 

 monly somewhat raised above the medium in the form of 

 drops) are more frequent than the thin, delicate, iridescent 

 growths, which are the rule in the Bact. typhi (19, n). 



(6) Magnified seventy times : Not to be differentiated with 

 certainty from Bact. typhi (compare 17, i),but on account 

 of the greater thickness of the film, the beautiful striking 

 system of furrows is rarely well developed in Bact. coli 

 (19, in, iv, and vi). We have often observed the deep 

 colonies, which, as a rule, are roundish or whetstone- 

 shaped (compare 17, v, and 15, vn ; both types are very 

 frequent), present wonderful, drawn-out, lobulated, tailed 

 forms, which remind one of the zooglea3 of Bact. vulgare, 

 and for which we can make only high temperature (soft- 

 ness of the gelatin) responsible (19, i). Similar forma- 

 tions have since been described by W. Rosenthal (Deut. 

 Arch. klin. Med., LV, 513). Compare also the complete 

 representation of Klie, who observed and represented 

 such forms of colonies of typhi and coli bacteria, espe- 

 cially upon soft nutrient media, containing little gelatin 

 (C. B. xx, 49). 



Gelatin Stab and Streak. Like Bact. typhi, only 

 somewhat thicker, more opaque, and more rapidly grow- 

 ing. Never liquefying (18, I, n). 



Agar Plate. Colonies exactly like Bact. typhi, only 

 usually somewhat thicker and moister. Magnified seventy 

 times, the deep colonies often appear somewhat rough and 

 knobby (18, vi), the superficial usually roundish, finely 

 punctated, almost structureless, and opaque; at other times 

 they are finely lobulated, with markings like a mulberry. 



