328 TEXT-BOOK OF BACTERIOLOGY. 



cutaneous tissue or the serous cavities, it produces purulent changes 

 distinguished by a pronounced inclination to spread slowly and to 

 continue its existence without " breaking down " and often mani- 

 festing an especially malignant character. 



Quite a number of other micro-organisms have been obtained 

 from pus; they are, however, but rarely observed, are only of 

 subordinate significance, and prove harmless by the result of ex- 

 periments on animals. It suffices to mention their names: the 

 Micrococcus pyogenes tenuis, the Bacillus pyog. foetidus, and the 

 Staphyloccocus cereus albus and flavus. 



XXIV. BACILLUS PYOCYANEUS. 



Another pyogenic bacterium, the bacillus of green or blue pus, 

 Bacillus pyocyaneus, deserves a more detailed notice. The pus from 

 a wound and the bandages sometimes become suddenly discolored 

 green or blue, in the majority of cases without disturbing the heal- 

 ing process. The cause of this striking phenomenon has been found 

 by Gessard to be a particular bacillus often found in non-purulent 

 serous wound secretion and even in the sweat of the skin. 



It is a small, slender rod, of the same shape and appearance as 

 the bacillus of blue milk, but rather narrower. It shows distinctly- 

 rounded ends, frequently unites in groups of four to six members, 

 but forms long threads only exceptionally. It is exceedingly 

 mobile ; sporulation has not been observed. It thrives at ordinary 

 and at breeding temperatures, and belongs to the semi-anaerobic 

 species. 



On the plate the colonies appear to the naked eye as small 

 white dots at the bottom of the gelatin ; they rapidly advance to 

 the surface and extend there as rather flat, moderately large, and 

 irregularly-circumscribed aggregations. The medium soon as- 

 sumes a green fluorescent color in the neighborhood of the colony. 

 The gelatin begins to gradually soften and the plate is usually en- 

 tirely liquefied on about the fifth day. 



Under the microscope the smaller and deeper colonies present 

 roundish, coarsely-granulated heaps with serrated borders of a yel- 

 lowish-green and shining hue. The superficial ones form delicate 

 laminae with a smooth depression of finely-granulated texture, dis- 

 tinctly greenish in the centre and paler toward the edges. They 

 then sink into the gelatin, become surrounded with a liquefied 

 region, and are transformed into a dense and indistinct mass. 



In the test-tube, growth takes place almost exclusively in the 

 upper portions of the inoculation puncture. On the surface of the 



