188 ASIATIC CHOLERA. 



ures as a short curved rod, from 0.8 to 2 mikrons in length, 

 by 0.3 to 0.4 mikron in breadth. Sometimes two of these 

 rods are united together by either end, with the convex sur- 

 face looking different ways, appearing then as the Roman 

 letter S ; at other times a number of the rods are united 

 together forming a long spirillum. These latter forms are 

 especially seen in older cultures. In young cultures the rods 

 are generally single or lying together and parallel to each 

 other. This peculiar mode of grouping serves in the recogni- 

 tion of this bacterium. 



The Spirillum cholerce Asiaticce stains with all the anilin 

 dyes, but rather poorly. It seems to have a more active 



FIG. 66. 



**A 



Spirillum of Asiatic cholera. Impression Involution-forms of the spirillum 



cover-slip from a colony thirty-four hours of Asiatic cholera, as seen in old 

 old. (Abbott.) cultures. (Abbott.) 



affinity for the fuchsin dye. It does not stain by the Gram 

 method. Young cultures take the stain much more readily 

 than older cultures, and in these what is known as involution- 

 forms long, thready filaments of different thickness are often 

 found. The spirillum contains no spores, but has only a 

 flagellum at one end (Figs. 66 and 67). 



Biologic Characters. The comma bacillus is strictly aerobic, 

 and though it grows in an atmosphere in which the oxygen 

 is diminished, it cannot grow in the absence of this gas. 

 This fact is the cause of its surface growth in fluid media. 



It is an artificially motile spirillum, especially when lately 

 obtained from cholera cases or in young cultures. It grows 



