580 SUMMARY OF CURRENT RESEARCHES RELATING TO 
clogging tlie filter, which can thus be mechanically cleaned more easily. 
The author finds that the use of this powder in no way alters the 
chemical composition of the water, only absorbs about one-tenth of the 
gases dissolved in the water, and has no influence on the bacteria 
therein. 
The filter will continue to deliver germless water for quite 10 days, 
provided the pressure be not more than 1 or 2 atmospheres, which the 
Andre regulator provides for. The filter should be sterilized every 
10 days or oftener, and this is better done by means of alcohol or alum 
than by heat. 
Natural Pure Cultivations of Skin Fungi.* — Dr. P. G. Unna pro- 
cures scales and crusts which he wishes to examine, by pressing on the 
diseased portions of skin zinc plaster-mull for some minutes, so 
that on removal the scabs adhere to it. They are then placed first 
in benzin and afterwards in hydrochloric acid alcohol, by which they 
are freed from the plaster. The pieces are then placed on a slide and 
stained for 15 minutes in strong anilin- water gentian- violet solution. 
They are next dried and treated for two or three minutes with an iodine 
solution (5 per cent, iodide of potassium and peroxide of hydrogen solu- 
tion, of each equal volumes). After this they are again dried, and 
thereupon immersed for 2 to 12 hours in picro or eosin-anilin. 
Demonstrating Sulphuretted Hydrogen generated by Bacteria.| — 
M. Orlowski availed himself of Fromme’s method for demonstrating the 
disengagement of H 2 S by bacteria, the basis of which method is the 
presence of a metallic salt in the medium ; thus Fromme added to pep- 
tonized gelatin 3 per cent, of tartrate or saccharate of iron, and culti- 
vated thereon very successfully bacteria of anthrax and typhoid fever, 
the medium being stained black owing to the development of H 2 S. 
The author extended the research in two directions by observations 
on a large number of different species, and by the use of several kinds 
of chemical substances. To the ordinary cultivation media (gelatin was 
chiefly used) the chloride or sulphate of iron, the lactate, sulphate, or 
acetate of copper, the iodide or basic acetate of lead, and also the nitro- 
prussiate of soda were added. On media of the foregoing composition, 
numerous different species of organisms were cultivated with the result 
that while the copper salts strongly retarded growth, the iron, lead, and 
nitro-prussiate in no way interfered with it. 
Bacillus typhosus, B. coli commune, B. neapolitanus, and bacillus of 
malignant oedema generate sulphuretted hydrogen as is shown by the 
discoloration of the medium containing iron. B. typhosus gives the 
strongest evidence, the medium along the track being quite black from 
the second day. On the nitro-prussiate gelatin the positions are re- 
versed, for J3. typhosus imparts only a faint blue colour at the end of 
the track, while with B. coli and malignant oedema the colour is deep 
or bright blue. With lead salts the results were similar to those for 
iron, a deep black stain along the inoculation track with B. typhosus on 
the second day. 
* Monatshefte f. Prakt. Dermatol., 1894, No. 6. See Central!)!, f. Bakteriol. u. 
Parasitenk, xv. (1894) pp. 701-2. 
f Wratsch, 1893, No. 48. See Ann. de Micrographie, vi. (1894) pp. 120-2. 
