486 PATHOGENIC AEROBIC BACILLI 



varying greatly in length, being sometimes short oval, and at others 

 from 1.25 to 3.75 /* in length ; also grow out into flexible filaments, 

 which may be more or less wavy or spiral in form. The short rods 

 are commonly seen in pairs ; they have terminal flagella ; involution 

 forms are frequently seen, the most common being spherical bodies 

 about 1.6 //in diameter. In old cultures in bouillon, or in cultures 

 made in meat infusion in the incubating oven, the short oval forms 

 greatly predominate, but in recent cultures in nutrient gelatin fila- 

 ments of considerable length are encountered in association with 

 shorter rods. 



Stains readily with fuchsin or gentian violet not so well with 

 the brown aniline colors ; does not stain by Gram's method (Cheyne). 



Biological Characters. Anaerobic and. facultative anaerobic, 

 liquefying, motile bacillus. Grows rapidly in the usual culture 

 media at the room temperature. 



The growth upon gelatin plates (five per cent of gelatin) at the 

 room temperature is very characteristic ; at the end of six or eight 

 hours small depressions in the gelatin are observed, which contain 

 liquefied gelatin and grayish- white masses of bacilli. Under a low 

 power these depressions are seen to be surrounded by a marginal 

 zone consisting of two or three layers, outside of which is a zone of a 

 single layer, from which amoeba-like processes extend upon the sur- 

 face of the gelatin. These processes are constantly undergoing 

 changes in their form and position, and may become separated from 

 the mother colony, or remain temporarily attached to it by a narrow 

 thread consisting of bacilli ; after a time the entire surface of the 

 gelatin is covered with wandering, amoeba-like colonies ; these 

 rapidly cause liquefaction, which by the end of twenty-four to forty- 

 eight hours has reached a depth of one millimetre or more over the 

 entire surface. The deep colonies also are surrounded by processes 

 projecting into the gelatin, which may be observed to suddenly ad- 

 vance and again to be retracted towards the central zoogloea-like 

 mass. Liquefaction around the colony rapidly progresses, and 

 actively motile rods and spiral filaments may be seen about the peri- 

 phery of this liquefied gelatin, while about it is a radiating crown of 

 irregular processes, some of which may be screw-like or corkscrew- 

 formed. In ten-per-cent gelatin the migration of surface colonies, 

 above described, is not observed. In gelatin stick cultures liquefac- 

 tion occurs along the entire line of puncture, and soon the contents 

 of the tube are completely liquefied ; near the surface of the liquefied 

 gelatin the growing bacilli form a grayish-white cloudiness, and at 

 the bottom of the tube an abundant flocculent deposit is formed. 

 Upon the surface of nutrient agar a rapidly extending, moist, thin, 

 grayish- white layer is formed. Upon potato this bacillus produces a 



