552 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
if the quantity of the virus inoculated be sufficiently large, be evident in 
three hours. This reaction is much better obtained if a few loopfuls of 
a cholera cultivation be placed on a white porcelain dish and then a 
loopful of sulphuric acid added, than in the usual way of pouring acid 
over a cultivation. 
Present Position of the Bacteriological Diagnosis of Cholera.* — 
Prof. K. Koch discusses the diagnosis of cholera under several heads, 
viz. microscopical examination, cultures in pepton solution, on gelatin 
and agar plates, cholera red reaction, experiments on animals. 
The author regards a microscopical examination of the alvine dis- 
charge as most important. Some of the mucoid secretion found in the 
motions or in the intestinal canal after death should be used for making 
cover-glass preparations, and these stained with dilute Ziehl’s fuchsin 
solution. In cases of cholera such preparations are nearly always 
successful and frequently show the characteristic arrangement in clusters 
of the cholera bacilli. 
The diagnosis is then to be confirmed by cultivating the organism 
simultaneously in pepton and gelatin. The tubes are incubated at 22° 
and 37° respectively. In 8 hours the pepton cultivation will have suf- 
ficiently developed to give the cholera red reaction if the cholera vibrio 
be present. In 20-24 hours the gelatin plates show the cholera colonies. 
Where there is considerable doubt at the first, agar plates should also be 
employed, and these inoculated from the pepton cultures after they have 
incubated for 6 hours, and 10 hours later the diagnosis may be con- 
firmed by the red indol test. 
Sometimes the cholera organisms develope slowly and in small 
numbers, both in pepton and gelatin. If in these there be none, but on 
agar some suspicious looking colonies, then a completely new set of 
cultures on all three media must be started and when ready submitted to 
the sulphuric acid test and experiments made on animals. 
Cultures in pepton solutions are made by adding a few drops of the 
choleraic dejecta or a small quantity of mucus from the stools with a 
platinum loop to a sterilized 1 per cent, solution of pepton mixed with 
0*5-1 per cent, of sodium chloride, and the reaction of the solution 
must be alkaline. The cultures are incubated , at 37°. The pepton 
cultivations should be confirmed by gelatin plate cultivations. These 
are made of 10 per cent, gelatin and incubated at 22°. In 15-24 hours 
characteristic colonies will be apparent. On agar plates the colonies 
are of medium size and of a brownish-grey colour. 
The cholera red reaction is regarded by the author as extremely 
important since the cholera vibrio is the only comma-shaped organism 
which gives the reaction. The reaction consists in the formation of a 
red colour when pure H 2 S0 4 is added to a cultivation, and is due to the 
presence of indol and nitrous acid. 
Experiments on animals are of importance since the cholera spiril- 
lum is the only one known which when injected into the peritoneal 
sac produces toxic effects. About 15 decimilligrammes— about as much 
as can be picked up on a platinum loop — is removed from an agar cul- 
tivation, mixed with a cubic centimetre of broth, and injected into the 
* Zeitschr. f. Hygiene, xiv. No. 2. See Medical Week, 1893, pp. 265-9. 
