36 APPLIED BACTERIOLOGY 



Milk may not only be deprived of its fat l^y means of 

 these cylinders, l)ut a clear sterile serum is obtained. 



For experimental purposes these filters must be sterilised 

 and cleaned before being used. This operation does not 

 affect the Pasteur filter, but tends to disintegrate the 

 Berkfeld, which after a time loses its sterilising power. 



iNG Microtome. 



pressed under a pressure of 

 asteur tubes steeped in water 

 is a trustworthy test of their bacterial soundness, as bubbles 

 escape from any fault. 



The Microtome. — A large number of machines for the 

 cutting of sections of tissues have been introduced by 

 various makers. 



