SYSTEMATIC AND DESCRIPTIVE. 



305 



upper part of the medium a smoky brown (Plate 

 II., Fig. 2). 



The bacilli can also be cultivated in milk and on 

 various other substrata, as potatoes (Plate XXL), 

 boiled rice, and starch. A pure cultivation in 

 neutralised sterile milk develops a weak alkaline 



': ! 



FIG. 119. BACILLUS CYANOGENUS, x 650. 



A. Active rods. B. Rods in zoogloea. C. Chain of short rods. D. Chain of 

 cocci. E. Cocci stage. F, G. Spore -forming rods. H. Involution-forms 



[After Neelsen]. 



reaction. The colouring matter which is formed, 

 varies with the nourishing medium ; for example, 

 in milk a slate-blue coloration is produced, but 

 if the milk has become acid by the growth of 

 the Bacillus acidi lactici, then the colour is an 

 intense blue 



The micro-organism occurs occasionally in 



20 



