416 APPLIED BACTERIOLOGY 



was caused by a microbe, whicli, however, he was unable 

 to cultivate owing to the imperfect bacteriological methods 

 employed at the time. The bacillus of 'blue milk' is 

 known as the Bacillus cyanogenus or Bacterium syn- 

 cyaneum of Ehrenberg. 



B. cyanogenus. — The bacillus of blue milk consists of 

 small motile rods, which are provided with abundant 

 flagella. The organism is pale-blue in colour, does not 

 liquefy gelatine, which, however, is stained bluish-green, 

 finally becoming of a dirty grayish tinge. On potatoes 

 the growth occurs as a thick, dirty-yellow layer, which 

 afterwards becomes blue ; the medium is discoloured. 

 The organism- is described at length by Hueppe (Mitth. 

 a.d.k Gesundheitsamt, ii., p. 335), and by Heim {Arbeiten 

 a.d.k. Gesundheitsamt, v., p. 518), and figured in Lehmann 

 and Neumann's Atlas. It gives an alkaline reaction, and 

 produces neither coagulation nor acidity. It usually yields 

 two pigments, one of the ordinary fluorescent type, and the 

 other of a bluish to grayish colour, which becomes more 

 strongly blue up to azure in unsterilised milk with an 

 acid reaction. The addition, for instance, of Bacillus acidi 

 lactici a day or two after syncyaneus has been introduced 

 into the milk shows this very clearly. The addition of 

 soda or potash produces a pink coloration. Numerous 

 other organisms are also capable of turning milk blue. 

 SchoU {Fortschr. d. Med., 1889) isolated six bacilli which 

 had this capacity. 



Red Milk. — Several organisms may give rise to this 

 disease in milk, the chief of which is the red milk bacillus 

 of Hueppe (B. lactis erythrogenes) , which is described in 

 detail by Grotenfeldt (Fortschr. d. Med., 1889, ii., p. 41). It 

 gives milk a red coloration, which is developed best when 

 the medium is slightly alkaline and kept in the dark, and is 

 checked by acidity and light. On standing, the cream rises 



