ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
241 
reagent is added. In a few seconds a red colour appears. The hue 
varies somewhat with the nutritive medium. The reagent may be used 
for solid as well as for liquid media, though the results with agar are less 
effective and much slower in developing than with gelatin. 
For using this test two points must be borne in mind : — (1) that some 
commercial peptons will often give a reaction, because they contain 
nitrous acid (the “ peptonum siccum ex albumine ” is free from this 
objection) ; (2) fluid gelatin will also give the reaction. Hence the 
cultures should be laid in ice before applying the reagent, which also 
should be cold. In this way confusion between the colour from the 
organisms and that of the medium is avoided. 
The reagent was tried with more than 30 bacteria, Vibrio cholerse 
asiaticse giving the most characteristic reaction. With V. Metchnikovi 
the reaction was weaker, and with other vibrios of Finkler- Prior, Muller, 
Deneke there was none at all. The author states that Bacterium coli 
commune gives the reaction, but adds in a note that sometimes there was 
failure. There was no reaction with B. typhi abdominalis and many 
others. 
In conclusion, the author points out that this nitrous acid reaction 
is superior to the indol reaction in that it can be obtained in a shorter 
time, that it can be used for pepton and gelatin cultures, that the colour 
developed is more intense, and that it can distinguish between cholera 
bacilli on the one hand and the Finkler-Prior and Muller’s bacteria on 
the other. 
Hens’ Eggs as a Cultivation Medium for the Cholera Vibrio.* — 
Hrs. E. Abel and A. Draer have investigated the suitability of hens’ eggs 
for growing the cholera vibrio. The material worked with was obtained 
from cholera faeces, from intestinal cholera corpses, and from old culti- 
vations. From each source four eggs were inoculated and incubated at 
37°. On the 8th, 14th, 18th and 2lst days one egg from each of these 
stocks was examined especially for H 2 S, and for alterations of colour 
and consistence. Microscopical preparations were made, and also 
cultures in pepton water and bouillon, on gelatin plates, on agar, and 
also on agar by the pyrogallic acid method. 
Direct egg to egg inoculation was also tried in order to ascertain if 
any micro-organisms had been overlooked owing to their small numbers. 
The authors concluded that the hen’s egg is a very unsuitable cultivation 
medium ; that the cholera vibrio is present as a pure cultivation, both 
when the yolk is of golden-yellow colour and when it is greenish black. 
The explanation of these facts seems to be due on the one hand to the 
impurities which naturally exist in the egg, and on the other to dif- 
ferences in the derivation of the vibrio, some having considerable power 
of blackening the y»»lk, others very little, and again, the number of 
organisms introduced appears to have a certain influence. It was further 
found that the cholera vibrios developed H 2 S in some eggs, and in others 
not. 
Plaster and Brick Blocks for growing Yeast.f — M, J. C. Nielsen 
contests the statement made by Wichmann J relative to the blocks for 
* Ontralbl. f. Bakteriol. u. Parasitenk., l e Abt., xvii. (1895) pp. 85-7. 
t C.R. Travaux Laboratoire de Carlsberg, iii. (1894) p. 179. 
% See this Journal, 1894, p. 127. 
1895 
R 
