IO6 BACTERIOLOGICAL DIAGNOSIS. 



thicker. It is slightly curved, hence the name of the 

 " comma bacillus," the comparison being to a German 

 comma ; it looks very like a caraway seed (Plate II., 

 fig- 5)- 



In the carbol-fuchsin specimen vast numbers of these 

 curved rods will be seen ; probably few other organisms, 

 if any, will be present if the case is one of true cholera. 

 Two or more rods may often be found joined together 

 with their concavities turned in opposite directions, 

 giving the whole the appearance of a very elongated 

 spiral. In the stools (but not usually in cultures) the 

 individual rods have frequently a parallel arrangement, 

 presenting the appearance of " shoals of fish swimming 

 up stream." 



If you see these appearances examine the Gram 

 specimen. Very few organisms will be visible, as the 

 cholera vibrio does not retain the stain when treated in 

 this way. 



If vibrios having the above characters are present 

 proceed as follows : 



3. Take two or three small flasks (preferably steri- 

 lised by heat) and add to each 100 c.c. of water, i 

 gramme of peptone, and \ gramme of common salt ; 

 boil thoroughly and allow to cool. This forms a culture 

 medium in which the cholera vibrio will grow very 

 rapidly and other organisms far more slowly. 



Inoculate each flask with a loopful or two of dejecta ;. 

 plug each with cotton-wool and incubate for 8 to 12 

 hours at 37 C. If cholera vibrios are present the 

 cultures will conform to the following tests : 



a. There will be a film on the surface. This will be 

 more marked after a few hours longer. 



b. This scum will present the microscopic appear- 

 ances described above, except that the vibrios are 



