322 Suppuration 



known as Bacillus fluorescens liquefaciens, from which Ruzicka* 

 thinks it has probably descended. 



Staining. It stains well with the ordinary staining solutions, but 

 not by Gram's method. 



Isolation. The isolation of the organism is simple, the ordinary 

 plate method being a satisfactory means of securing it from pus 

 or other discharges. 



Cultivation. Colonies. The superficial colonies upon gelatin 

 plates are small, irregular, slightly greenish, ill-defined, and produce 

 a distinct fluorescence of the neighboring medium. 



Microscopic examination shows the superficial colonies to be 

 rounded and coarsely granular, with serrated or slightly filamentous 

 borders. They are distinctly green in the center and pale at the 



'~ 



Fig. 115. Bacillus pyocyaneus. Colonies- upon gelatin (Abbott). 



edges. The colonies sink into the gelatin as the liquefaction pro- 

 gresses. Four or five days must elapse before the medium is all 

 fluid. 



Gelatin Punctures. In gelatin puncture cultures the chief de- 

 velopment of the organisms occurs at the upper part of the tube, 

 where a deep saucer-shaped liquefaction forms, slowly descending 

 into the medium, and causing a beautiful fluorescence. At times a 

 delicate scum forms on the surface, sinking to the bottom as the 

 culture ages, and ultimately forming a slimy sediment. 



Agar-agar. Upon agar-agar the growth developing all along 

 the line of inoculation at first appears bright green. The green 

 color depends upon a soluble pigment (fluorescin) which soon 

 saturates the culture-medium and gives it the characteristic fluores- 

 cent appearance. As the culture ages, or if the medium upon which 

 it grows contains much peptone, a second blue pigment (pyocyanin) 

 develops, and the bright green fades to a deep blue-green, dark blue, 

 or in some cases to a deep reddish-brown color. This pigment has 



* "Centralbl. f. Bakt. u. Parasitenk.," July 15, 1898, p. n. 



