770 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
alleviation, when the application was made immediately after inoculation ; 
at a later stage there was little result. Thirdly, they applied the 
current to affected tissues surrounded by distilled water, salt solution, 
or potassium iodide solution. In many cases the effect was very 
distinctly ameliorative. 
Pleochroism of Stained Bacteria.* — The optical properties of the 
cell-membrane of bacteria have been examined by Herr J. Amann, who 
observes that the problem to be solved consists in determining whether 
the cell-membrane behaves like single or double refracting crystals, and 
in the second alternative whether these optical properties are in accord 
with those of uni- or bi-axial crystals. The technical difficulties in study- 
ing such a question are great, since on account of their composition and 
tenuity the doubly refracting properties of the bacterial membrane are 
so slight that they would be with difficulty perceived by the usual 
method of examination with the polarizing apparatus. The bacteria 
must therefore be stained, and anthrax stained with malachite-green 
was found to possess pleochroistic properties. The conclusions drawn 
by the author from his observations are that the cell-membrane of certain 
Schizomycetes, when stained with some suitable pigment, shows a clear 
though faint pleochroism, and it is therefore doubly refracting. In 
anthrax the maximum absorption occurs when the longitudinal axis of 
the bacillus is placed vertical to the plane of the polarized ray. The 
optical behaviour of the stained anthrax bacilli makes it very probable 
that the pigment exists in the crystalline condition in the cell-mem- 
brane, and that the pigment crystals must be so disposed that their 
longitudinal axis is vertical to the long side of the bacterial cell. This 
view is supported by the fact that artificially stained bacteria, observed 
in a suitable manner, constantly show the colour of the pigment crystals. 
Formation of Sulphuretted Hydrogen by Bacteria.y — Dr. Stagnitta- 
Balistrera has found that the formation of H 2 S gas by bacteria is much 
more extended than is usually supposed, and depends partly on a definite 
organization of the protoplasm, and partly on the composition of the 
pabulum. Only aerobic germs were used in the experiment, and on 
analysis the following quantity of sulphur was found in the media : — 
Bouillon 0-0705, pepton-bouillon 0*2131, pepton-agar 0*3016, 10 per 
cent, gelatin 0*7051 grm. 
H 2 S is best demonstrated when the medium is solid by the iron- 
gelatin employed by Fromme, made by adding the saccharate, tartrate, or 
acetate of iron to ordinary gelatin. When the nutrient medium is liquid, 
the simplest and most sensitive reagent is moistened lead paper sus- 
pended within the flasks; 0*03 mg. H 2 S from 50 ccm. of fluid give a 
clear reaction (slight brown colour) : the lead papers must be examined 
at least daily, as the evidence of a reaction may disappear. 
The first experiments were made on solid media, while in the latter 
ones liquid media were used, and that which seemed to give the best 
results was simple bouillon. 
Out of thirty-five organisms examined, eighteen were found to have 
* Centralbl. f. Bakteriol. u. Parasitenk., xiii. (1893) pp. 775-80. 
t Arch. f. Hygiene, xvi. pp. 10-31. See Centralbl. f. Bakteriol. u. Parasitenk., 
xifi. (1893) pp. 755-7. 
