598 PATHOGENIC SPIRILLA. 
Bolton’s experiments (1887) mercuric chloride was effective in two 
hours in the proportion of 1:10,000 ; sulphate of copper, 1 : 500. 
The low thermal death-point and comparatively slight resisting 
power for desiccation and chemical agents indicate that this spiril- 
lum does not form spores, and most bacteriologists agree that this 
is the case. Hueppe, however, has described a mode of spore for- 
mation which is different from that which occurs among the bacilli, 
viz., the formation of so-called arthrospores ; these are said to be 
developed in the course of the spiral threads, not as endogenous re- 
fractive spores, but as spherical bodies which have a somewhat 
greater diameter than the filament and are somewhat more refrac- 
tive. This mode of spore formation has not been observed by Kita- 
sato and other bacteriologists who have given attention to the ques- 
tion, and cannot be considered as established. In competition with 
the ordinary putrefactive bacteria the cholera spirillum soon disap- 
pears, and, as determined by Neffelman and by Kitasato, they only 
survive for a few days when mixed with normal feces. 
A test for the presence of the cholera spirillum has been found 
by Bujwid and by Dunham in the reddish-violet color produced in 
bouillon cultures containing peptone, or in cultures in nutrient gela- 
tin, when a small quantity of sulphuric acid is added to the culture. 
According to Frankel, this test serves to distinguish it from the ordi- 
nary bacteria of the intestine and from the Finkler-Prior spirillum, 
but not from Metschnikoff’s spirillum (‘‘ vibrio”). The reaction is 
shown by bouillon cultures which have been in the incubating oven 
for ten or twelve hours, and by gelatin cultures in which liquefac- 
tion has occurred. The sulphuric acid used should be quite pure ; 
the color quickly appears and is reddish-violet or purplish-red. Ac- 
cording to Salkowski, the red color is due to the well-known indol 
reaction, which in cultures of the cholera spirillum is exceptionally 
intense and rapid in its development. A test which is said to dis- 
tinguish cultures of the cholera spirillum from the spirillum of De- 
neke and that of Finkler-Prior, has been proposed by Cahen. This 
consists in adding a solution of litmus to the bouillon and in making 
the culture at 37°C. The cholera cultures show on the following 
day a decoloration which does not occur at this temperature with the 
other spirilla named. 
For determining as promptly as possible whether certain suspected 
excreta contain cholera spirilla, a little of the material may be used 
to inoculate greatly diluted bouillon, gelatin plates being made at 
the same time. At the end of ten or twelve hours the cholera spiril- 
lum, if present, will already have formed a characteristic wrinkled 
film upon the surface ; a little of this should be used to start a new 
culture in diluted bouillon, and a series of gelatin plates made from 
