340 RUEDIGEU. 



appreciable loss of immune bodies. During the last three years large 

 quantities of immune serums have been filtered with great success. The 

 Berkefeld filter marked W usually furnishes a germ-free filtrate under 

 a pressure of two atmospheres or less. If a much higher pressure is 

 used germs appear to be forced through occasionally. 



In order to avoid rapid clogging of the filter the serum should be 

 centrifugated before filtration is attempted, and the filters must be 

 cleansed thoroughly immediately after being used. 



