60 PRINCIPLES AND PRACTICE OF MILK HYGIENE 



Staphylococcus pyogenes albus and aureus are similar in 

 so many respects that all are regarded by some bac- 

 teriologists as different varieties of the same species. 

 The optimum temperature for the udder cocci is 35 to 

 37 C. (95 to 98.6 R), but they grow well at much 

 lower temperatures, development continuing down to 

 freezing. The peptonizing action is exerted at these 

 low temperatures. 



Many of the peptonizers are spore-forming bacteria. 

 The most common representatives of this division are 

 the hay bacillus (Bacillus subtilis) and the potato bacillus 

 (Bacillus mesentericus vulgatus). They belong to a 

 large group of organisms which are very numerous in 

 cultivated soil and are consequently found on all products 

 of the soil, especially hay, straw, roots, etc. They are 

 large rod-shaped bacteria with rounded ends. The spores 

 form in the middle or end of the organism without chang- 

 ing its shape. On agar plates these bacteria form dry, 

 thin, superficial skin-like colonies, with irregular borders. 

 The colonies have a tendency to extend over the surface 

 of the media and are consequently called " spreaders." 

 These organisms are very numerous in the dust of hay 

 and other dry fodder, also in straw, and they may get 

 into the milk in large numbers if the fodder or litter is 

 brought into the stable and distributed a short time before 

 milking, or if dust from hay or other dry fodder is per- 

 mitted to sift down into the stable through cracks in the 

 ceiling. When a cow lies upon bedding or upon loose 

 soil, these bacteria enter the folds and creases of the 

 skin and become attached to the hair, and when the cow 

 is milked those upon the udder, flanks and surrounding 

 parts are dislodged and may fall into the milk pail. 

 These organisms are especially numerous on the hair 



