NON- PATHOGENIC BACTERIA 95 



Properties. Very motile; dissolves gelatin. 



Growth. Rapid; strongly aerobic. 



Plate. Round, gray colonies with depressed white center. 

 Under microscope the center yellow; the periphery like a wreath, 

 with tiny little rays projecting; very characteristic. 



Potato. A thick moist skin forms in twenty-four hours. 



Staining. Rods, ordinary stain; spores, spore stain. 



It is easily obtained by covering finely cut hay with distilled 

 water, and boiling a quarter of an hour. Set aside forty-eight 

 hours. A thick scum will show itself on the surface, composed 

 of the subtilis bacilli, whose spores alone have survived the heat. 



Bacillus Spinosus (Luderitz). Called spinosus because 

 small spine-like processes are formed by the colonies. 



Origin. In the juices of the body of a mouse and guinea-pig 

 which were inoculated with garden-earth. 



Form. Large rods, straight, some slightly bent, ends 

 rounded; often in long threads. 



Properties. Large spores, the bacillus enlarging to allow the 

 spores to develop; very motile; gelatin slowly liquefied. A 

 gas is formed in the culture having an odor like Swiss cheese. 



Growth. The growth occurs at 20 C. temperature only 

 when the oxygen is excluded. Very strongly anaerobic. Glu- 

 cose added to the gelatin (i to 2 per cent.) increases growth. 



Colonies in roll cultures and high stab-cultures appear as little 

 spheres surrounded by a zone of liquefied gelatin. In the 

 deeper growths thorn-like projections or spines develop, pro- 

 ceeding from a gray-colored center. 



Staining. With ordinary methods. 



Some Bacteria Found in Milk. Bacillus Acidi Lactici 

 (Huppe). Belongs to the same group as the Bacillus coli com- 

 munis. (See p. 137.) 



Origin. In sour milk. 



Form. Short thick rods, nearly as broad as they are long, 

 usually in pairs. 



Properties. Immotile. Spores, large shining ones. Does 

 not liquefy gelatin. Breaks up the sugar of milk into lactic acid 

 and carbonic acid gas, the casein being thereby precipitated. 



