98 ESSENTIALS OF BACTERIOLOGY 



Stab-culture. Grows mainly on surface; a nail-like growth. 

 The surrounding gelatin becomes colored brown. 



Potato. The surface covered with a dirty blue scum. 



Attenuation. After prolonged artificial cultivation loses the 

 power to produce pigment. 



Staining. By ordinary methods. 



Bacillus Lactis Erythrogenes (Bacillus of Red Milk) 

 (HUppe and Grotenf eldt) . Origin. Found in red milk and 

 in the feces of a child. 



Form. Short rods, often in long filaments, without spores. 



Properties. Does not possess self-movement. Forms a 

 nauseating odor; liquefies gelatin. Produces a yellow pigment 

 which can be seen in the dark, and a red pigment in alkaline 

 media, away from the light. In milk it produces the yellow 

 cream on top of the blood-red serum, or fluid in the center, 

 and at the bottom the precipitated casein. 



Growth. Grows rapidly in bouillon and on potatoes; slower 

 on the other media. Plates. A cup-like depression in the 

 center of the colony, with a pink coloration around it, the colony 

 itself being slightly yellow. 



Stab-culture. The growth mostly on surface. The gelatin 

 afterward colored red and liquefied. 



Potato. A golden-yellow pigment formed at 37 C. after six 

 days. 



Examination of Milk in Stained Specimen. A drop of 

 milk diluted with a drop of distilled water is dried on the cover- 

 glass and fixed by heat. Chloroform methylene blue, prepared 

 by mixing 12 to 15 drops of saturated alcoholic solution of 

 methylene blue with 3 or 4 c.c. of chloroform, is used for stain- 

 ing. The chloroform is then evaporated by exposing the speci- 

 men for a few minutes to the air. Bacteria blue; rest of field, 

 unstained. 



Another method is to mix a drop of milk with two or three 

 drops of a i per cent, solution of sodium carbonate on a cover- 

 glass. Saponification of the fat occurs on heating the mixture 

 to evaporation. The preparation is then stained in the ordinary 

 manner. 



