366 BACTERIOLOGY. 



cholera, and as Koch's " comma bacillus," because of 

 its morphology, is identified by the following peculi- 

 arities : 



THE MORPHOLOGICAL AND BIOLOGICAL PECULIARITIES 

 OF THE SPIRILLUM OF ASIATIC CHOLERA. 



Morphology. It is a slightly curved rod varying from 

 about 0.8 to 2.0^ in length and from 0.3 to 0.4 /j. in 

 thickness that is to say, it is usually from about one- 

 half to two-thirds the length of the tubercle bacillus, 

 but is thicker and plumper. Its curve is frequently 

 not more marked than that of a comma, and, indeed, it 

 is often almost straight; at times, though, the curve is 

 much more pronounced, and may even describe a semi- 

 circle. Occasionally the curve may be double, one 

 comma joining another, with their convexities pointing 

 in opposite directions, so that a figure similar to the 

 letter S is produced. In cultures long spiral or undu- 

 lating threads may often be seen. From these appear- 

 ances this organism cannot be considered as a bacillus, 

 but rather as an intermediate type between the bacilli 

 and the spirilla. Koch thinks it not improbable that 

 the short comma forms represent segments of a true 

 spirillum, the normal form of the organism. (Fig. 71.) 



It does not form spores, and we have no reliable evi- 

 dence that it possesses the property of entering, at any 

 time, a stage when its powers of resistance to detrimental 

 agencies are increased. 



It is a flagellated organism, but has only a single 

 flagellum attached to one of its ends. 



It is actively motile, especially in the comma stage, 

 though the long spiral forms also possess this property. 



