78 



THE PRESERVATION OF SERUMS METHODS 



panying illustration (Fig. 35) is quite serviceable, as the flask and 

 earthen candle-filter may be wrapped in a towel and sterilized in the 

 autoclave. The apparatus may carefully be attached to a suction 

 pump, and the serum pipeted off into the hollow of the candle and fil- 

 tered, the filtrate being removed, at the completion of the process, by 

 another sterile pipet. 



FIG. 35. A FILTER. 



The cotton plug in the " candle" is removed and the fluid poured within the 

 candle (hollow). The water is then turned on and the stop-cocks are opened; a 

 vacuum is produced within the flasks, which draws the fluid through the candle. 

 The filter is readily cleansed and sterilized (autoclave) and is quite efficient. 



Care should be exercised regarding the reaction of Berkefeld filters 

 and particularly new filters. Before use they should be boiled in distilled 

 water at least three times for five minutes each time, and scrubbed with 

 a small soft brush after each boiling. After the filter is set up, hot, 

 neutral, distilled water should stand in it for about five minutes and then 



