596 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
Indol Reaction in Diphtheria Cultures.* * * § — MM. Palmyrsky and 
Orlowsky find that old diphtheria cultures (three weeks) give the 
cholera-red reaction with hydrochloric and sulphuric acids. Young 
cultures do not give the cholera-red reaction. For the reaction to 
succeed, the presence of indol and of nitrites is necessary. In young 
cultures the latter are absent or in such small quantities that, notwith- 
standing the presence of indol, the reaction fails. 
Colour Reaction of Nitrous Acid on Cultivations of Cholera and 
other Bacteria.! — While the indol reaction is common to many bacteria 
and is therefore not a specific test, yet according to M. Lounkewitsch 
the Griess-Islovay reagent possesses the special power of detecting 
1 per million of nitrous acid by staining the medium a deep red. The 
reagent is composed of (P10 grm. naphthylamin in 20 grin, distilled 
water and 0*5 grm. sulphanilic acid in 150 grm. acetic acid. The 
desired effect is produced by adding to the culture one-fifth of its 
volume of the reagent. The colour is produced with cholera cultures 
6-21 hours old, or with cultures of Vibrio metschnilwvi 21-48 hours old. 
The reagent also produces the colour with the coli bacillus and the 
bacillus of mouse typhoid, but not with the bacillus of Eberth or with 
the vibrios Finkler-Prior, Muller, Dencke. The reaction recommended 
by the author and called by him the nitrous acid reaction to distinguish 
it from the red indol reaction of Bujwid and Dunham, has the following 
advantages. It .may be obtained with cultures 6, 12, 24 hours old, 
while the indol reaction cannot before 24-48 hours. It manifests itself 
in a few’ seconds, while the indol reaction does not appear till after tw r o 
or more hours. It can be used with both pepton and gelatin cultures. 
The colour is deep and bright, while that of the indol is quite pale. 
The cholera red reaction is unable to distinguish the vibrios Finkler- 
Prior, Deneke, Ac., from the cholera vibrio, while the Griess-Islovay 
reagent can. 
Simple Method of Isolating Acid-producing Bacteria.! — In the 
study of the bacteriology of milk it is often desirable, says Prof. H. W. 
Conn, to obtain all the acid organisms separate from the alkaline pro- 
ducing species, and this may be done as follows : — An ordinary beef- 
pepton-gelatin solution is made to which is added 3 per cent, milk- 
sugar and enough normal litmus solution to give a deep purplish colour. 
Plates are then made in the ordinary manner. Wherever an acid 
organism is present it produces acid from the milk-sugar, and the acid 
turns the litmus red. The result is that after a day or two the plates 
begin to be dotted over with little red spots, and these when isolated 
are the acid-producing organisms. 
Cultivating Crenothrix polyspora on Solid Media.§ — Herr Bossier 
succeeded in cultivating Crenothrix polyspora on pieces of brick steri- 
lised by heat. To the water was added some sulphate of iron, as the 
fungus only thrives in ferruginous waters. After some time at the room 
* Medycvna, 1895. See Ann. de Microgr., vii. (1895) p. 268. 
t Wratsch, 1895, No. 1. See Ann. de Microgr., vii. (1895) pp. 2G7-S. 
% Micr. Bull., xii. (1895) p. 4. 
§ Arch. d. Pharmacie, ccxxxiii. (1895) p. 189. See Centralbl. f. Bakteriol. u. 
Parasitenk., l te Abt., xviii. (1895) p. 25. 
