886 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
and hydrocarbonaceous matter was retained. This retaining power 
became diminished by use, and also after sterilization of the bougies, 
and in all cases the toxicity of the filtrate was lowered. Hence the 
author considers that mineral filters have a distinct hygienic value, but 
are not sufficiently accurate for scientific purposes. 
Permeability of the Chamberland Filter to Bacteria.* — Dr. E. 
von Freudenreich finds that the Pasteur-Chamberland filtering apparatus 
will produce germ-free water for at least eight successive days, and that 
therefore it may be used for household and laboratory purposes pro- 
vided that it is sterilized every week, and that the temperature of the 
water does not exceed certain limits (15°-18°). 
Procedure for Obtaining Germ-free Water.f — Drs.V. and A. Babes 
describe an apparatus for obtaining germ-free water ; the vessel itself is 
of zinc or glass, having the 
shape of an Erlenmeyer’s flask, 
and capable of holding 20-40 
litres (fig. 103). At the bottom 
is a pipe with stop-cock for 
letting off the water, and at 
the side an aperture, closed by 
a screw-tap, for cleansing pur- 
poses. The vessel having 
been filled with water, 3-6 
grms. of powdered alum are 
put in, and then stirred up 
with a flat perforated piece of 
wood, or by means of a per- 
forated mixer turned by a 
handle. When thoroughly 
stirred up the mixer is re- 
moved and the vessel covered 
with a cap. In 18-20 hours 
the water is drawn off by the 
tap at the bottom. It is ad- 
visable to let the first half- 
litre lun off. The principle 
on which the apparatus and 
procedure are founded is that 
of sedimentation and decanta- 
tion, and though alum acts 
very well other substances 
may be used, such as sulphate 
of iron or chalk. A similar 
result was obtained by currents 
of air, but the details are not 
given. The authors think that 
the results of their methods 
are very encouraging and infinitely superior to any of the filtration 
methods, all of which are condemned as being worse than useless. The 
* Centralbl. f. Bakteriol. u. Parasitenk., xii. (1892) pp. 240-7 (1 fig.), 
t Tom. cit., pp. 132-8 (1 fig). 
