BACILLUS COLI COMMUNIS. 185 



Biologic Characters. It is aerobic and facultative anaerobic. 

 It is motile at times, and at other times appears to be motion- 

 less. Its motility is always of the sluggish kind. Cultures 

 which when young contain organisms with decided motion, 

 have on being kept for some time sho\vn that the bacilli have 

 lost their motility. It grows on all the artificial culture- 

 media and at the temperature between 10 and 40 C. Its 

 growth, though retarded at the temperature above 40 C., 

 is not altogether stopped until 45 C. is reached. Exposure 

 to a temperature of 65 C. for five minutes destroys the bac- 

 teria. Exposure to cold has no effect on the bacteria, and in 

 some instances the author has been able to cultivate bacteria 

 which had been exposed to the temperature of liquefied air 

 for several minutes. 



In bouillon the bacillus grows very rapidly and renders the 

 bouillon cloudy ; pellicles are formed on the surface of the 

 medium, and there is also a thick deposit at the bottom of 

 the tube. A strong fecal odor can be detected. 



On gelatin plates the colonies appear as small, spherical, 

 blue-gray points, somewhat dentated at the margin. With a 

 magnifying glass the colonies are brownish, lozenge-shaped 

 or irregularly round, coarsely granular. In gelatin stab- 

 cultures along the track of the needle are seen a series of 

 small spherical colonies in rows and separated from each other. 

 On the surface of the tube the growth is of a dirty gray 

 color. It does not liquefy gelatin. 



On agar-agar the growth has nothing characteristic. On 

 agar to which 2 per cent, glucose has been added bubbles may 

 b,e seen along the line of growth, due to the gases of fermen- 

 tation. On lactose-litmus-agar the colonies develop very 

 rapidly and are of a pinkish color. On potato it grows rap- 

 idly in the beginning, being of a bright-yellow color which later 

 becomes brown. The growth in serum is similar to that on agar. 



It produces indol in peptone solution and coagulates milk 

 very rapidly. It ferments lactose- and glucose-bouillon. A 

 type of B. coli, styled by Dunham Bacillus coli communior, 

 has been isolated. It is supposed to bo a distinct variety. 

 The only present known difference from B. coli communis is 



