THE BIOLOGY OF MICROBES, ETC. 161 



scleroma ; and it has been proved by Alvarez 1 to be 

 the cause of the indigo fermentation and the pro- 

 duction of indigo-blue. Indigo-blue or indigotin is 

 the product of several plants belonging to the 

 Indigofera and other genera. It does not exist 

 in these plants ready - formed, but is produced 

 by the decomposition of a glucoside (C 26 H 31 N0 17 ) 

 called indican. By the action of Alvarez's bacillus, 

 indican yields indigo-blue (C 8 H 5 NO) and indiglucin 

 (C 6 H 10 6 ):- 



,, + 2 H 2 = C 8 H 6 NO + 3 C 6 H 10 6 . 



The bacillus of indigo fermentation has been 

 shown to possess pathogenic properties, and oc- 

 casions in animals a transient local inflammation, 

 or death, with visceral congestion and fibrinous 

 exudations. 



Bacillus pyocyaneus. This microbe is a very 

 minute, short, thin rod ; and it is said to produce 

 spores. It occurs in chains of twos or threes, or 

 collected into irregular masses ; and it has been 

 isolated from pus of those cases in which the wounds 

 exhibit a greenish-blue colour. According to Dr. 

 Gessard, 2 B. pyocyaneus produces a greenish pigment 

 of a definite composition, which has been called 

 ' pyocyanin.' Pyocyanin can be extracted from pus 

 by means of chloroform. Dr. J. Kunz 3 has grown 

 this microbe on nutrient gelatine kept for three or 

 four days at the ordinary temperature, and then for 



1 Comptes Rendus de I' Academic des Sciences, tome 105. 



2 De la Pyocyanine et de son Microbe, 1882. 



3 Monatsheftefur Chemie, Bd. ix. p. 361. 



T 



