446 BACTERIOLOGY. 



" comma bacillus," is identified by the following peculi- 

 arities : 



SPIRILLUM CHOLERA ASIATICS. 



Morphology. — It is a slightly curved rod, ranging 

 from about 0.8 to 2 /i in length and from 0.3 to 0.4 /i 

 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 tlie 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. 75.) 



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

 dence that it possesses the property of entering, at any 

 time, a stage in which its powers of resistance to detri- 

 mental 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. 



Groxiping. — As found in the slimy flakes in the intes- 

 tinal discliarges from cholera patients, Koch likens its 

 mode of grouping to that seen in a school of small fish 



