162 A MANUAL <_.'/ Lt 



seven days at 35 C. It liquefies the gelatine, which 

 shows a green fluorescence, and has the specific 

 smell of blue pus. Kunz extracted from the lique- 

 fied gelatine pyocyanin and pyoxanthose, but the 

 liquid still showed a green fluorescence due to a 

 distinct colouring matter, which is only soluble in 

 water and alcohol, and is not destroyed by boiling. 

 Concentrated solutions of this colouring matter 

 transmit red and green light only, but dilute solu- 

 tions have no absorptive power. According to 

 Kunz, pyocyanin contains nitrogen and sulphur. 

 The green pigment which is formed when this 

 bacillus is grown on nutrient gelatine is most pro- 

 bably produced by the oxidizing action of the air 

 on a chromogen which is formed by the bacillus, as 

 the pigment is not contained in the bacillary cells. 

 In gelatine solutions, the green colour disappears 

 gradually at the ordinary temperature in ten or 

 fifteen weeks, giving place to a dark reddish-brown 

 colour, and the reaction becomes strongly alkaline. 

 B. pyocyaneus grows in milk, and produces a 

 yellowish-green solution, which becomes intensely 

 green when ammonia is added. 



The chemistry of the microbian pigments is a 

 subject which has been very little investigated ; but 

 these pigments are undoubtedly products formed 

 from the decomposition of albuminoids by the 

 agency of microbes. 



Bacillus septiccemice (rabbit). This microbe, which 

 is pointed at both ends, measures T4 x 0*7 p. It 

 occurs singly and in chains; and it grows in bouillon, 

 nutrient gelatine, and blood serum. On gelatine- 



