i88 MICRO-ORGANISMS AND DISEASE [chap. 



character in gelatine plates is sufficient to identify it : after 

 twenty-four hours at 20° C. it first forms grey, circular colonies, 

 already depressed and liquefying ; after forty-eight hours the 

 colonieshavemuch increased and are now liquefied, depressed, 

 turbid, circular patches with a distinct greenish tinge of 

 colour. When the colonies are numerous and closely placed 

 the plate may by this time be altogether liquefied, the fluid 

 gelatine tuibid and of greenish, fluorescent tint. In gelatine 

 stab culture the liquefaction proceeds from the upper part 

 of the stab, the lower part being made up of a row of 

 greyish-white dots. The appearance of a plate culture and 

 of a stab culture after twenty-four to thirty-six or forty-eight 

 hours' incubation, as also of the individual bacilli seen under 

 the microscope, looks exactly like those figures of the Bacillus 

 radicicola mentioned in a former chapter (Chapter VI), the 

 liquefied gelatine being fluorescent, greenish. Soon the 

 liquefaction extends throughout the whole culture. On 

 Agar also the greenish, fluorescent colouration is pronounced, 

 the surface growth itself being brownish, translucent. Under 

 the microscope the bacilli are thin and cylindrical, motile, 

 singly or in dumb-bells, or in filaments ; they do not form 

 spores. They grow best at lower temperatures up to 22° C., 

 but grow also at 37° C, only not so well in comparison. 



6. Bacillus coli communis (Escherich). — The typical 

 bacillus of faecal matter, of the intestinal contents of man 

 and animals ; and occurs also in all solids and fluids to 

 which intestinal discharges have had access. It is sometimes 

 present in nasal, oral, and pectoral discharges. It occurs 

 (due to secondary invasion from the intestine) in abdominal 

 inflammatory processes : abscess of the liver, spleen, 

 peritoneum ; ' in pulmonary and bronchial suppurations ; in 

 ulceration and abscesses of the skin and mucous membranes 

 open to contamination with filth. Its primary home ap- 



