STEEILISATIOX 



which for experimental purposes is required to be 

 .sterilised without chemical change, these Chamberland 

 .and Berkefeld filters are extremely useful (see experi- 

 ments made by Percy Frankland on the vitality of the 

 anthrax bacillus in various waters, p. 314 ; the sterility 

 of the water was secured by means of a Chamberland 

 filter). In those cases in which it is desired to separate 

 the bacterial products from the micro-organisms them- 

 selves such filtration is invariably resorted to. Bitter l 

 has made experiments on the filtration of liquids turbid 

 from the growth of bacteria, and also of albuminous 

 fluids, by means of the Berkefeld filter. He has found 

 that even the bacillus of mouse septicaemia, which is one 

 of the smallest known organisms, growing in broth, is 

 entirely removed when the latter is passed through the 

 .above filter. Experiments were also made with blood- 

 .serum, and it was found that even putrid blood-serum 

 may be not only quickly clarified, but the organisms 

 entirely removed by its means. For this purpose it is 

 best to use the more porous cylinders. Such a cylinder 

 was found capable of filtering 680 c.c. in twenty-five 

 minutes. In the case of fresh serum a cylinder of 

 similar construction yielded in thirty minutes 800 c.c. 

 of clear sterile serum. It is necessary to frequently 

 wipe the cylinder whilst the filtration is going on. Milk 

 may also be deprived of all its fat and a clear sterile 

 serum obtained by filtration through such porous cylin- 

 ders. For the subsequent cleansing of the filter see 

 p. 176. This method of sterilisation, therefore, may 

 be used with great advantage for many laboratory 

 purposes. 



Gases, again, are readily deprived of any micro- 

 organisms they may contain in suspension by passage 



1 ' Die Filtration bacterientriiber und eiweisshaltiger Fliissigkeiten 

 <durch Kieselguhrfilter.' Zeitschriftfiir Hygiene, x. 1890, p. 155. 



