NON-PATHOGENIC BACTERIA. 77 



Plate Colonies. First small white points, which soon look like 

 porcelain, glistening. Under microscope the surface colonies 

 resemble leaves spread out. 



Stab Culture. A thick dry crust with cracks in it forms on the 

 surface after a couple of weeks. 



Attenuation. If cultured through successive generations, they 

 lose the power to produce fermentation. Several other bacteria 

 will give rise to lactic acid fermentation ; but this especial one 

 is almost constantly found, and is very wide spread. 



In milk, it first produces acidity, then precipitation of casein, 

 and finally, formation of gases. 



A bacillus described by Grotenfeldt, and called Bacterium 

 Acidi Lactici, forms alcohol in the milk. It was found in milk 

 in Bavaria. 



Bacillus Butyricus. (Hiippe.) 



This bacillus causes butyric acid fermentation. 



Origin. Found in milk. 



.Form. Short and long thin rods with rounded ends; large 

 oval spores, seldom forming threads. 



Properties. Very motile ; liquefies gelatine rapidly ; produces 

 gases resembling butyric acid in odor. In milk it coagulates the 

 casein, decomposes it, forming peptones and ammonia, with a 

 bitter taste, and butyric acid fermentation. 



Growth. Quickly, at 35 to 40 0., with oxygen. 



Colonies. Plate. Small yellow points which soon run together, 

 becoming indistinguishable. 



Stab Culture. A small yellow skin formed on the surface with 

 delicate wrinkles ; cloudy masses in the liquefied portion. 



Staining. With ordinary stains. 



Bacillus Amylobacter (Van Tiegham) ; or, Clostridium Buty- 



ricum. (Prazmowsky.) 



Origin. Found in putrefying plant-infusions, in fossils, and 

 conifera of the coal period. 



Form, Large, thick rods, with rounded ends, often found in 

 chains. A large glancing spore at one end, the bacillus becoming 

 spindle-shape in order to allow the spore to grow ; hence the 

 name clostridium. 



