332 Manual of Veterinary Microbiology. 



This coloring matter is most abundantly produced 

 at about 20°, in less amount at 25°, and not at all at 

 37°. The pigment is a soluble substance which gives 

 a red reaction with potash, violet with ammonia. 

 Inoculation of this germ to animals produces no re- 

 sult. 



The infection of milk takes place after its with- 

 drawal from the udder and is contingent upon a pre- 

 vious infection of the dairy or of the stable. 



Cheese made from infected milk may also show 

 this blue color, but the latter changes more or less 

 to green in consequence of the yellow color which 

 cheese assumes in aging. 



Red milk. — Two species of germs are capable of 

 imparting a red color to milk. One, the micrococcus 

 j^rodigiosus, is elliptical, motile, and forms on potato 

 an abundant slimy growth of blood-red color. The 

 infected milk shows on the surface a pellicle of a 

 more or less deep red color, the deeper layers remain- 

 ing unaltered. Another, the bacterium lactis erythro- 

 gbies, is a very short non-motile rod. In milk it 

 slowly precipitates the casein and the whole mass as- 

 sumes a blood-red color. 



Red milk is of much rarer occurrence than blue 

 milk. 



Yellow milk. — This deterioration occurs especially 

 on boiled milk ; golden yellow patches appear on the 

 milk which, at the same time, coagulates and becomes 

 alkaline. The change is produced by the growth of 

 the bacillus synxanthus, a slender, very mobile rod. 



Bacterial hcemoglobinuria of cattle. 

 This acute febrile disease prevails in an endemic 



