NON-PATHOGENIC BACTERIA. 79 



away from the light. In milk it produces the yellow cream on 

 top of the blood-red serum, or, fluid in the centre, 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 centre 

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

 being slightly yellow. 



Stab Culture. The growth mostly on surface. The gelatine 

 afterwards colored red and liquefied. 



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

 days. 



Some Non-Pathogenic Bacteria found in Water. The bacteria 

 found here are very often given to producing pigments or phos- 

 phorescence, and are in great number. The more common ones 

 only will be described. 



Bacillus Violaceus. 



Origin. Water. 



Form. A slender rod with rounded ends, three times as long 

 as it is broad, often in threads ; middle-sized spores. 



Properties. Very motile ; forms a violet-blue pigment, which 

 is soluble in alcohol, and depends upon oxygen for its growth. 

 Rapidly liquefies gelatine, but not agar. 



Growth. Grows fairly quick, is facultative anaerobic. 



Cultures on Plate. At first the colonies look like inclosed air- 

 bubbles. Low power shows irregular masses, with a centre 

 containing the pigment and a hairy-like periphery. 



Stab Culture. Cone-like liquefaction containing air, and the 

 pigment, in separated granules, lying towards the bottom. 



Stroke Culture on Agar. A violet, ink-like covering which 

 remains for years. 



Bacillus Coeruleus. (Smith.) 



Origin. Schuylkill water. 



Form. Very thin rods ; 2.5 /*. long, 0.5 /t*. wide ; often in 

 threads ; spores were not found. 



Properties. Liquefies gelatine; produces a very deep-blue 

 pigment. 



Growth. Slowly, with oxygen, at ordinary temperature. 



Plate. Round colonies on the surface of bluish color. 



