i82 PRACTICAL BACTERIOLOGY. 



Sbaining is easily done wifcli any aniline dye, but is 

 especially successful when a solution of fuchsine is 

 used. The bacilli are then seen with the microscope 

 to be rodlets, about -5^0 mm. in length and about 

 2-oVo nim. in breadth, with distinctly rounded-oflf 

 ends. Two to four often hang together, but the 

 separate cells are clearly marked off one from another ; 

 only rarely, and then invariably in fluid nutrient 

 media, are large collections formed. All its culti- 

 vations have a most unpleasant smell, like decom- 

 posing egg albumen. 



4. Bacillus pyocyaneus. 



The greenish-blue coloration often present in pus 

 and the dressings of suppurative wounds is caused by 

 the action of a colouring matter formed by the bacillus 

 pyocyaneus, an organism which until the last few 

 years has been looked upon as a harmless inhabitant 

 of dressings. Recent observations, however, show 

 that it is not so innocent, but that in addition to 

 thriving well in the pus, caused by other organisms, 

 it itself possesses the power of exciting suppuration. 



It may be very easily obtained from pus, and then 

 used for plate cultivations. Even on the second day 

 small turbid spots are seen in the gelatine, and soon 

 afterwards a greyish-white point may be observed in 

 the centre, from which delicate threads stretch out 

 into the medium. The appearance of the colony 

 keeps changing; at first brighter rings are formed 



♦ * 



