BACILLUS PYOCbTANEUS 199 



faction. In thrust-cultures the gelatine liquefies along the 

 needle-track, the fluid mass assuming a greenish colour, 

 while the jDart still solid displays a green fluorescence. A 

 layer forms upon agar which shows a fluorescence, at first 

 greenish, but subsequently dark green in tint ; while on 

 potato the deposit appears coloured brown, turning red 

 when treated with acids, blue with ammonia. According to 

 Gessard, the generation of pigment depends on the nutrient 

 medium. The green colouring matter formed, which is 

 soluble in chloroform, has received the name oipyocyanin. 



Eabbits die when injected into the peritoneal cavity 

 with pure cultures of this micro-organism or with 

 pyocyanin. 



The Bacillus pyocyaneus /3, described by Ernst, is not 

 pathogenic, but is commonly met with in the company of 

 the foregoing, and when isolated causes the 

 blue coloration of pus. It hquefies gelatine i* .. ^ ,° 

 much more speedily than the last, and shows ^""^^ •> 

 a brown tint on potato which changes to *• 



grey on touching with the platinum wire vm. 75.— isolated 



ElJiMESTS OP 



(the chameleon vhenoynenun) . The reaction bTAPHTLocooous 



' CEEEUS PLAVUS. 



of the potato culture, the more rapid lique- 

 faction, and the fact that injections produce no result, all 

 serve to distinguish it from Bacillus pyocyaneus a. 



With reference to its physiological relations, Bacillus 

 pyocyaneus produces coagulation of milk, rapidly peptonises 

 albumen, and causes vigorous inversion of sugar with fer- 

 mentation. 



Staphylococcus cereus. — Passet found in pus the Staphy- 

 lococcus cereus alhus and Staphylococcus cereus flavus, the 

 cocci of which are arranged in minute clumps (fig. 75). 

 The former produces upon the gelatine plate white dots 

 which spread out superficially and do not liquefy the 

 medium. In thrust-cultures a white deposit is likewise 



