NON-PATHOGENIC BACILLI. 



667 



gin is irregular; when the colony reaches the surface a very slow liquefac- 

 tion of the gelatin commences and the appearance of the colonies becomes 

 very characteristic. From the yellowish- brown centre twisted bundles of 

 filaments are given off which are at first also of a yellowish-brown color, 

 but gradually become colorless toward the periphery. In gelatin stick cul- 

 tures development is extremely slow ; upon the surface a small, yellowish 

 mass is formed at the point of puncture, while the line of inoculation is 

 scarcely visible ; liquefaction occurs later and the liquefied gelatin is clouded ; 

 when liquefaction has once commenced it progresses more rapidly. Upon 

 the surface of agar a glistening, yellowish layer is developed which extends 

 but little beyond the impfstrich. In bouillon a diffuse cloudiness is pro- 

 duced and a whitish sediment is seen at the bottom of the tube; no film is 

 formed upon the surface. Upon potato scarcely any development occurs 

 a faint yellowish stripe along the impfstrich only. Reduces nitrates with 

 formation of ammonia. 



352. BACILLUS DIPFUSUS (Frankland). 



broad; solitary or in 



Found in the soil. 



Morphology. Bacilli about 1.7 j^ long and 0.5 

 pairs; also grow out into long, flexible filaments. 



Biological Characters. An aerobic, liquefying bacillus. Exhibits ro- 

 tatory and oscillatory movements only. Spore formation not observed. 

 Grows in the usual culture media at the room temperature. Upon gelatin 

 plates the superficial colonies after a time have a very characteristic ap- 

 pearance; they extend from the original 

 centre as a broad, thin, bluish-green layer. 

 Under a low power the deep colonies re- 

 semble colonies of the cholera spirillum; 

 they are nearly sphei'ical, coarsely gran- 

 ular, and have somewhat jagged mar- 

 gins ; later the margins are still more ir- 

 regular and finely dentate, while the 

 surface near the margin appears coarsely 

 granular; when the colonies come to the 

 surface the centre is no longer well de- 

 fined, but remains granular, while about 

 it a very characteristic surface growth 

 occurs. In gelatin stick cultures the 

 development is almost limited to the sur- 

 face, upon which a smooth, thin, shin- 

 ing, somewhat greenish-yellow layer is 

 formed; liquefaction of the gelatin be- 

 neath this progresses very slowly. Upon 

 the surface of agar a very thin, shining, smooth layer of a feebly yellow 

 or cream color is developed. In bouillon a diffuse cloudiness is developed 

 and a greenish-yellow sediment is formed, while some flocculi may float 

 upon the surface, which, however, do not constitute a film. Upon potato a 

 thin, smooth, shining, faintly greenish-yellow layer is formed. 



FIG. 220. FIG. 221. 



FIG. 220. Bacillus diffusus, from a gela- 

 tin culture. X 1,000. (Frankland.) 



FIG. 221. Bacillm diffusus; superficial 

 colonies in nutrient gelatin. X 100. 

 (Frankland.) 



353. BACILLUS LIQUIDUS (Frankland). 



Found in river water from the Thames ; very common. 



Morphology. Short and thick bacilli with round ends; usually in pairs, 

 of which the length varies from 1.5 to 3.5 M ; differ greatly in dimensions. 



Biological Characters. An aerobic, liquefying, motile bacillus. Spore 

 formation not observed. Grows at the room temperature in the usual cul- 

 ture media. Upon gelatin plates the deep colonies, under a low power, are 

 seen to be spherical, with smooth outlines ; when liquefaction commences 



