78 BACTERIOIvOQICAL EXAMINATION OF MILK. 



III. MILK ANOMALIES. 



The so-called disease of milk, or "milk anomalies,'' 

 often have their origin in the action of the presence of 

 micro-organisms. The most important of these anoma- 

 lies are the following: 



/. Red Milk. This is caused by different sapro- 

 phytic (non-pathogenic) genii of bacteria : Sarcina spe- 

 cies, Bacillus prodigiosus. Bacillus lactis erythrogenns, 

 Bacillus rubidus. Spirillum rubrum, Micrococcus cinna- 

 bareus, and by a red yeast. 



(a) Of the Sarcina, the most common are Sarcina 

 rosea Menge, Sarcina rosea Schrotter and Sarcina au- 

 rantiaca. The different species, of which numerous germs 

 are found in the air, are distinguished from one another 

 by their readiness or slowness in liquefying gelatine. 

 Aurantiaca does not liquefy gelatine, and grows very 

 slowly. All grow upon the ordinary culture media and 

 are strongly aerobic. 



(b) The Bacillus prodigiosus is a very small, short 

 rod, possessing no motion. It grows as well at room 

 temperature as at 37 degrees and liquefies gelatine. At 

 incubation temperature there is no pigmentation, the 

 latter condition going hand in hand with the production 

 of trimethylamine (odor like that of pickled herring). 



A dark red color is beautifully shown upon potato 

 culture ; this becomes light red when treated with acetic 

 acid. Ammonia restores the original deep red color. 

 Sterile milk inoculated with Bacillus prodigiosus slowly 

 precipitates the casein ; the serum-zone beneath the layer 

 of cream gradually becoming blood red. 



(c) Bacillus lactis erythrogenus (Hueppe) liquefies 

 gelatine. In bouillon and solid culture media it pro- 

 duces a yellow pigment, while in milk and whey the 

 pigment produced is red. The red color is impaired by 

 light and acids. 



