480 PATHOGENIC AEROBIC BACILLI 



ture more rapidly in the incubating oven. Is a facultative anae- 

 robic (Frankel). Does not form spores. The thermal death-point, 

 as determined by the writer, is 56 C., the time of exposure being ten 

 minutes. In gelatin plate cultures colonies are quickly developed, 

 which give to the medium a fluorescent green color ; at the end of 

 two or three days liquefaction commences around each colony, and 

 usually the gelatin is completely liquefied by the fifth day. Before 

 liquefaction commences the deep colonies, under a low power, appear 

 as spherical, granular masses, with a serrated margin, and have a 

 yellowish-green color ; the superficial colonies are quite thin and 

 finely granular ; at the centre, where they are thickest, they have a 

 greenish color, which fades out towards the periphery. 



In stick cultures in nutrient gelatin development is most abun- 

 dant near the surface, and causes at first liquefaction in the form 

 of a shallow funnel ; later the liquefied gelatin is separated from 

 that which is not liquefied by a horizontal plane, and a viscid, yel- 

 lowish-white mass, composed of bacilli, accumulates upon this sur- 

 face, which gradually has a lower level as liquefaction progresses ; 

 the transparent, liquefied gelatin above is covered with a delicate, 

 yellowish-green film, and the entire medium has a fluorescent green 

 color. Upon nutrient agar a rather abundant, moist, greenish-white 

 layer is developed, and the medium acquires a bright green-color, 

 which subsequently changes to olive green. Upon potato a viscid 

 or rather dry, yellowish-green or brown layer is formed, and the 

 potato beneath and immediately around the growth has a green color 

 when freely exposed to the air or to the vapors of ammonia. In milk 

 the casein is first precipitated and then gradually dissolved, while at 

 the same time ammonia is developed. The green pigment is formed 

 only in the presence of oxygen; it is soluble in chloroform and may 

 be obtained from a pure solution in long, blue needles ; acids change 

 the blue color to red, and reducing substances to yellow. According 

 to Ledderhose, it is an aromatic compound resembling anthracene, 

 and is not toxic. According to Gessard's latest researches (1890), two 

 different pigments are produced by this bacillus, one of a fluorescent 

 green and the other pyocyanin of a blue color. Cultivated in egg 

 albumin the fluorescent green pigment, which changes to brown 

 with time, is alone produced. In bouillon and in media containing 

 peptone or gelatin both pigments are formed, and the pyocyanin 

 may be obtained separately by dissolving it in chloroform. In an 

 alkaline solution of peptone (two per cent) to which five per cent of 

 glycerin has been added the blue pigment alone is formed. 



Pathogenesis. The experiments of Ledderhose, Bouchard, and 

 others show that this bacillus is pathogenic for guinea-pigs and rab- 

 bits. Subcutaneous or intraperitoneal injections of recent cultures 



