THE CHOLERA SPIRILLUM 



401 



made from the intestinal contents in typical cases, these organ- 

 isms are present in enor- 

 mous numbers in almost 

 pure culture, most of the 

 spirilla lying with their 

 long axes in the same 

 direction, so as to give the 

 appearance which Koch 

 compared to a number of 

 fish in a stream. 



They possess very active 

 motility, which is most 

 marked in the single forms. 

 When stained by the suit- 

 able methods they are seen 

 to be flagellated. Usually 

 a single terminal flagellum 

 is present at one end 

 only (Fig. 135). It is 

 very delicate, and measures 



four or five times the length of the organism. In some varieties, 

 however, there may be a flagellum at both ends, or more than 

 one may be present ; cul- 

 tures obtained at different 

 places have shown con- 

 siderable variations in this 

 respect. Cholera spirilla 

 do not form spores. In 

 old cultures the organisms 

 may present great variety 

 in size and shape. Some 

 are irregularly twisted fila- 

 ments, sometimes globose, 

 sometimes clubbed at their 

 extremities, and also show- 

 ing irregular swellings along 

 their course. Others are 

 short and thick, and may 



FIG. 135. Cholera spirilla stained to show 

 the terminal flagella. x 1000. 



have the appearance of large 

 cocci, often staining faintly. 

 All these changes in appear- 

 ance are to be classed to- 

 gether as involution forms. 



Staining. -'Cholera spirilla stain readily with the usual basic 

 26 



FIG. 136. Cholera spirilla from an old agar 

 culture, showing irregularities in size and 

 shape, with numerous faintly - stained 

 coccoid bodies involution forms. 

 Stained with fuchsin. x 1000. 



