UDDER-COLIBACILLOSIS 63 



As a rule the size of the bacillus is regularly two to three 

 microns long. 



The vegetative colon bacillus forms a distinct but, in 

 comparison with its thickness, somewhat short rod with 

 rounded ends. It seldom reaches the unusual length of 

 eight microns, at which times it simulates a short thread. 

 Besides these vegetative specimens one always finds a num- 

 ber of shorter specimens which have an oval form and many 

 of which are also globular. The short forms are most numer- 

 ous in culture; they are less numerous in the animal body 

 -w^here the vegetative speci- 

 mens are present in the 

 greatest number. 



The colon bacillus oc- 

 curs mostly as a single ba- 

 cillus, but is also arranged 



in hneS consisting of two Fig. 14—Colonbacilliinmilk sediment. Carbol- 

 ,. . , , T 1 -I 'IT methylene blue. ( X 150.) Two different caees. 



mdividuals or diplobacilli, 



infrequently of three individuals or streptobacilh (Fig. 14) . 



They are easily stained by the common anilin dyes, 

 but are quickly and easily decolorized following Gram's 

 method. 



In preparations from animal bodies it is surrounded 

 by a bright halo like a capsule. This is perhaps an effect 

 produced by the flagella. 



The colon bacillus is motile or immotile.* 



Cultivation. — It grows best at body temperature 

 ( 38 ° C. ) , it also grows well at room temperature. It grows 



^ I classify the immotile bacterium lactis aerogenes (synonym: 

 b. acidi lactici) with the colon bacillus. The real colon bacillus is 

 motile, b. lactis aerogenes is immotile ; but in other morphological 

 and cultural characteristics these bacteria are very similar. The 

 real colon bacillus often forms " wander zones " in culture, which 

 formations are not produced by b. aerogenes. Both of these bac- 

 teria produce mastitis. 



