BACTERIA, NOT CLASSIFIED. 



715 



irregular. Grows slowly in the usual culture media at the room temperature. 

 Upon gelatin plates deep colonies are seen at the end of three days as well- 

 defined, small, brown points. The superficial colonies are at first shining and 

 opalescent ; under the microscope they are seen to be finely granular and 

 have smooth margins; at the end of five to eight days the colonies in con- 

 tact with the air commence to cause liquefaction of the gelatin ; liquefac- 

 tion progresses so slowly that evaporation keeps pace with it, and the colo- 

 nies slowly sink into the gelatin ; when the layer of gelatin is quite thin a 

 ring of liquefied gelatin may surround the colony. In gelatin stick cultures 

 a scanty gi-owth is seen along the line of puncture at the end of twenty-four 

 hours. Upon the surface a thin, irregular, whitish layer commences to 

 form around the point of inoculation at the end of three or four days; the 

 gelatin is slowly liquefied below this, and as a result of evaporation a small 

 cavity is formed which is lined with a thin layer of bacilli. But little de- 







c 



Fia. 263. FIG. 264. 



FIG. 263. Bacillus litoralis; A, colony upon gelatin plate, ten days old; B, gelatin stick culture 

 ten days old; C, bacilli from hanging-drop culture. (Russell.) 



FIG. 264. Bacillus halophilus; A, culture in nutrient gelatin at end of twenty -four hours; B 

 culture in sea-water gelatin at end of twenty- four hours. (Russell.) 



velopment occurs along the line of inoculation below, but the growth often 

 acquires a reddish-brown color, and the gelatin around it is stained brown 

 this color is only developed in the absence of oxygen. In streak cultures 

 white, semi-transparent colonies are formed along the line of inoculation ; 

 these become visible after the second day, extend slowly, and finally coal- 

 esce; in the course of five to seven days the thicker white colonies com- 

 mence to sink below the surface as a result of liquefaction and evaporation ; 

 liquefaction now progresses more rapidly, and after a time the deposit at the 

 bottom of the liquefied gelatin acquires a reddish-brown tint. No growth 

 occurs upon potato. Upon agar a scanty, thin, moist-looking, grayish-white 

 layer is formed. In bouillon a uniform cloudiness is developed and no pel- 

 licle forms upon the surface. 



