SPIRILLUM OF ASIATIC CHOLERA. 331 



This organism, known as the spirillum of Asiatic 

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

 morphology, is identified by the following peculiarities : 



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 fj. in length and from 0.3 to 0.4/* 

 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 oppo- 

 site directions, so that a figure similar to the letter S is 

 produced. In cultures, long spiral or undulating threads 

 may often be seen. From these appearances this organ- 

 ism 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. 64.) 



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. 



