106 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 IL, 
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, fF 
gramme of peptone, and 4 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 
