60 STERILIZATION OF CULTURE MEDIA. 
In Fig. 30 the Pasteur-Chamberland filter is shown as arranged 
for the filtration of water. A is the hollow porcelain cylinder, which 
is enclosed in a metal case, D. The metal case is tightly clamped 
against a projecting shoulder at the lower part of the porcelain filter, 
aring of rubber being interposed to secure a tight joint. When 
water under pressure is admitted to the space E, between the cylin- 
der of porcelain and the metal case, it slowly filters through, and, 
running down the inner wall of the filter, escapes at B into a recep- 
tacle placed to receive it. If we fill the space E with a liquid cul- 
ture of bacteria and apply sufficient pressure (one or two atmo- 
spheres), a clear filtrate is obtained which is entirely sterile if the 
porcelain filter is sound and made of proper material. After the 
Fie. 31. 
filter has been in use for some time, however, it may permit the pas- 
sage of bacteria, and it will be necessary to subject it to a high tem- 
perature for the purpose of destroying all organic matter contained 
in the porous porcelain. 
We may use the Chamberland filter without a metal case by im- 
mersing it in a cylindrical glass vessel containing the liquid to be fil- 
tered, as shown in Fig. 31. The porcelain cylinder is connected with 
an aspirator bottle, a, and a small Erlenmeyer flask, b, is interposed 
to catch the filtrate when it overflows from the interior of the filter. 
Of course all the necessary precautions must be taken with reference 
to the sterilization of the interior of the bougze, of the flask b, and of 
the rubber tube connecting the two. 
Another arrangement of the Pasteur-Chamberland filter for labora- 
tory purposes is shown in Fig. 32. In this form of apparatus a 
