BACILLUS PRODIGIOSUS. 353 



the colonies, which are afc first white, may be allowed to 

 grow till their surface presents a distinct red colour. 

 In puncture cultivations in gelatine there is rapid lique- 

 faction and formation of a reddish deposit ; in punc- 

 ture cultivations in agar, colourless colonies develop 

 sparingly along the track of the needle, while on the 

 surface the growth extends towards the margin of the 

 material, and gradually assumes a deep red colour. 



Bacillus prodigiosus grows very well on potatoes ; on 

 this material an intensely blood-red, moist layer is formed, 

 growing with a luxuriance and a production of a bright 

 colour not found in the case of any other bacterium. 

 When the cultivation has been kept for some time, the 

 surface of the red deposit presents a greenish shimmer, 

 similar to the appearance of crystals of fuchsine. Growth 

 also occurs on a great variety of other vegetable sub- 

 strata, it also takes place in milk, and in the latter 

 material the oil globules contain the red colouring matter 

 in solution. 



The bacilli themselves are colourless. The pigment Characters df 

 is insoluble in water, but soluble in alcohol ; its solu- e pl?m< 

 tion shows a characteristic absorption band both in the 

 green and in the blue portions of the spectrum. By the 

 addition of acid the colour changes to a carmine red, and 

 then to violet; when an alkali is added it becomes yellow. 

 The colouring matter is only formed when the colonies 

 of fungi are in contact with free oxygen. Hence the more 

 deeply seated colonies, and those which develop along the 

 track of the needle in puncture cultivations, are colour- 

 less. Not only do these bacilli produce pigment, but simultaneous 

 they also set up marked decomposition of albuminous jj| th?sub- tl0n 

 media, this change being characterised by the produc- stratum, 

 tion of a smell resembling that of trimethylamine, as 

 well as by the alkaline reaction of the gases which are 

 formed; this change has not as yet, however, been 

 accurately analysed. Bacillus prodigiosus appears not Distribution, 

 uncommonly as a spontaneous infection of articles of 

 food; the phenomena which were formerly repeatedly 

 observed of the so-called bleeding bread and the bleed- 

 ing host were probably caused by it ; in fact it occurs at 



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