SYSTEMATIC AND DESCRIPTIVE. 303 



doubtful results. The bacilli were isolated from 

 the diseased larvae of bees. 



Bacillus pyocyaneus (Micrococcus pyocyaneus, 

 Gessard. Bacterium aruginosum, Schroter. Ba- 

 cillus fluorescens). Slender rods sometimes linked 

 in twos or threes, or collected in irregular masses. 

 Spore-formation present. On plate-cultivations 

 white colonies with indistinct contour appear in 

 twenty-four hours, and the whole of the gelatine 

 has a greenish shimmer. In test-tube cultivations 

 the gelatine is liquefied, and coloured green by 

 reflected light, and a deep orange by transmitted 

 light (Plate V., Fig. i). On nutrient agar-agar 

 they form a white layer, and colour the medium 

 a pea-green. The pigment formed by the rods is 

 a definite principle, pyocyanin.* It can be ex- 

 tracted with chloroform from pus, and from washings 

 of bandages ; it is soluble in acidulated water, which 

 it colours red. In neutral solution it becomes blue. 

 It crystallises in chloroform in long needles ; and 

 forms sometimes lamellae and prisms. The rods 

 occur in the pus of those cases in which the wounds 

 and pus-stained bandages exhibit a greenish-blue 

 colour. 



Bacillus ianthinus (Bacterium ianthinum, Zopf. 

 Bacillus violaceus). Slender rods, about four times 

 their width in length, with rounded ends. They 

 also form threads, and are actively motile. Spore- 



* Gessard, De la Pyocyanine et de Son Microbe. Paris these. 

 1882. 



