NOT DESCRIBED IN PREVIOUS SECTIONS. 471 



transmitted light they are seen to have a brownish color ; upon the surface 

 a grayish-white, concentric layer is formed about the point of inoculation in 

 the course of five or six days, which later forms a disc with thickened mar- 

 gins. Upon the surface of agar the growth along the line of inoculation is 

 abundant and viscid. Does not grow well upon potato. Upon blood serum 

 forms transparent, drop-like colonies which have an opalescent appearance. 



Pathogenesis. Pathogenic for rabbits, guinea-pigs, hares, white mice, 

 and house mice. Death occurs in from six to twenty days. At the autopsy 

 the lymphatic glands ai'e found to be enlarged and to have undergone case- 

 ation ; the liver and spleen are enlarged, the lungs cedematous and occasion- 

 ally contain tuberculous-looking nodules. An abscess forms at the point of 

 inoculation. Bacilli are found in the blood, the lymphatic glands, and the 

 various organs. 



122. BACILLUS GINGIVJE PYOGENES. 



Synonym. Bacterium gingivse ^yogenes (Miller"). 



Obtained by Miller from an alveolar abscess and from deposit around the 

 teeth " in a filthy mouth." 



Morphology. Short and thick bacilli with rounded ends, one to four 

 times as long as broad ; occur singly or in pairs. 



Biological Characters. An aerobic and facultative anaerobic, liquefy- 

 ing bacillus. Grows rapidly in the usual culture media. Upon gelatin 

 plates it forms spherical colonies at the end of twenty-four hours, which 

 have a yellowish color and well-defined margin ; at the end of forty-eight 

 hours liquefaction has progressed so far that the colonies have become con- 

 fluent. In gelatin stick cultures liquefaction occurs rapidly in the form of a 

 funnel, at the bottom of which a white deposit is formed. Upon the surface 

 of agar a thick, moist growth occurs along the line of inoculation, which 

 under the microscope has a slightly greenish-yellow tint and a fibrillated 

 structure. 



Pathogenesis. Pathogenic for rabbits, guinea-pigs, and for white mice, 

 when injected into the cavity of the abdomen in comparatively small 

 amounts (0.25 cubic centimetre). At the autopsy peritonitis, sometimes 

 purulent, is observed. Death occurs in from ten to twenty-four hours. The 

 bacilli are found in the blood in small numbers. Subcutaneous injections in 

 the animals mentioned produce a local abscess only. 



123. BACILLUS DENTALIS VIRIDANS. 



Found by Miller in the superficial layers of carious dentine. 



Morphology. Slightly curved bacilli with pointed ends; solitary or in 

 paii-s. 



Biological CJiaracters. An aerobic and facultative anaerobic, non- 

 liquefying bacillus. Spore formation not observed. Grows in the usual 

 culture media at the room temperature. In gelatin plates the colonies are 

 spherical, and under a low power are colorless or have a slightly yellow tint ; 

 when not crowded they may present two or three concentric rings. In gela- 

 tin stick cultures growth occurs both upon the surface and along the line of 

 puncture. Gelatin cultures acquire an opalescent-green color. Upon the 

 surface of agar a thin growth with irregular margins occurs along the impf- 

 strich ; this is bluish by transmitted light and greenish-gray by reflected light 

 colorless under the microscope. 



Pathogenesis. Injections into the cavity of the abdomen of white mice 

 or of guinea-pigs usually cause fatal peritonitis in from one to six days ; the 

 bacilli are only found in the blood in small numbers, by the culture method. 

 Subcutaneous injections in the animals mentioned produce severe local in- 

 flammation and suppuration. 



124. BACILLUS PULP.E PYOGENES. 

 Obtained by Miller from .gangrenous tooth pulp. 



