STERILIZATION BY FILTRATION 127 
caogulated, etc. Such has been found to be the case as mentioned 
elsewhere. 
With the intermittent method the material is heated for twenty to 
thirty minutes on three successive days. On the first day the vegetative 
cells are killed. The second day’s heating will destroy those vegetative 
cells which have come from spores which passed through the first day’s 
heating. On the third day the process is simply checked up. 
te 
= ee atte 
Pea 
si Hi ei a ry " Ss 4 
' “4 
“_ ct at 
i es z ail rae a a 
“i 
Fig 40 —Bath for Sterilization at Low Temperatures (Inspissator). 
Inspissator. Some media which are used by,bacteriologists must 
be sterilized at low temperatures. For this purpose a serum coagulator 
or inspissator 1s used. The media 1s heated at from 57° to 60° C. 
for different lengths of time. Blood serum may be heated for periods 
of one hour or for a longer period at one time. 
STERILIZATION BY FILTRATION 
Filtration is an efficient method of sterilization which has certain 
distinct advantages over other methods. It leaves the filtrate sterile 
