BACTERIUM PYOCYANEUM. 281 



moist luster, is scarcely at all elevated, with a gray zone at 

 the periphery, and a sky-blue one at the center, and with 

 some diffusion of the pigment into the agar. Upon bouil- 

 lon there is a thick, tough, somewhat wrinkled, deep blue 

 pellicle, the bouillon becoming moderately turbid. Milk 

 is unchanged, the surface light blue. Upon potato a layer 

 is formed, which is light blue at first, and later becomes 

 dark blue to dark blackish-green. Potato becomes gray- 

 ish-green throughout. No gas is formed from grape-sugar. 

 We found a trace of the pigment soluble in glacial acetic 

 acid, but it is entirely insoluble in all ordinary solvents. 



Bacterium pyocyaneum. (Gessard, Flugge.) 

 L. and N. 



(Plate 24. J ) 



Synonyms. 2 — Bacillus pyocyaneus Flugge, Pseudo- 

 monas pyocyanea Migula, Bacillus of greenish-blue pus, 

 1 ' green or blue pus. ' ' 



Literature to 1893 by Jakowski (Z. H. XVI, 475). 



Microscopic Appearance. — Slender rods, often grow- 

 ing into threads. Thickness, 0.4 v; length, 1.4 to 6 An- 

 other authors have also observed transition forms, from 

 slender rods to short, plump, even almost round forms 

 (24, ix). 



Motility. — Actively motile by means of a polar flagel- 

 lum (24, x). 



Stains with anilin dyes and by Gram's method. 



Requirements as Regards Nutrient Media, Tem- 

 perature, and Oxygen. — Usually is a strict aerobe, but is 

 also cultivated from closed abscess cavities. Jakowski 

 (Z. H. xv, 474) has cultivated from an intestinal fistula a 

 form growing anaerobically and in carbonic acid. It is 

 not very particular as to nutrient media and grows rapidly 

 at room and incubator temperature. 



1 Our plate is painted from a culture which was not entirely typical, 

 as it only forms a little pyocyanin. The color may be much more 

 bluish-green. 



2 See page 285, et seq., for related forms. 



