CHOLERA SPIRILLUM: MORPHOLOGY. 315 



any time a stage when 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. 



Grouping. As found in the slimy flakes in the intes- 

 tinal discharges from cholera patients, Koch likens its 

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

 when swimming up stream, i. e., they all point in nearly 

 the same direction and lie in irregularly parallel, linear 

 groups that are formed by one comma being located 

 behind the other without being attached to it. 



F:g. 61. 

 B. 



■■i 





Involution forms of the spirillum ol Asiatic cholera, as seen in old cultures. 



On cover-slip preparations made from cultures in the 

 ordinary way there is nothing characteristic about the 

 grouping, but in impression cover-slips made from 

 young cultures the short commas will nearly always be 

 seen in small groups of three or four, lying together in 

 such a way as to have their long axes nearly parallel 

 to one another. (See Fig. 60.) 



In old cultures in which development has ceased, it 

 undergoes degenerative changes, and the characteristic 



