118 Manual of Veterinary 31icrobiology. 



Filtration. — Germs, like all solid particles, can not 

 pass through porous substances in which the pores 

 are very fine. Liquids filtered through such a sub- 

 stance are therefore sterilized. Hence, it is possible 

 to obtain sterilization by filtering through plaster of 

 Paris, amianth, or porcelain. 



Chamberland has constructed a filter for steriliza- 

 tion based upon this property. It consists of a hol- 

 low tube of porcelain, closed at one end; this tube is 

 immersed in the liquid to be sterilized and a vacuum 

 produced in its interior in any of the ordinary ways; 

 the sterile liquid passes into the interior of the tube. 

 The latter, of course, should have been previously 

 sterilized and be free from fissures. 



Ayitiseptic solutions. — Sterilization of instruments, 

 anatomical specimens, the hands, etc., should be ob- 

 tained by means of acidulated solutions of corrosive 

 sublimate at 2 to 1,000, carbolic acid at 5 per cent, or 

 creolin at 2 per cent. To obtain sterilization, the 

 objects, after thorough cleansing, must be washed 

 with these solutions. 



Culture media. 



The cultureof germs in artificial media necessitates 

 the presence in these media of all the principles es- 

 sential to their life, as well as the absence of all 

 noxious products. Each germ having special nutri- 

 tive requirements of its own, the ideal would be to 

 possess media especially appropriate for the diverse 

 pathogenic species. A perfect culture apparatus 

 ought to admit of the continual addition of nutri- 

 ment, with, at the same time, the elimination of the 

 residual products ; but this ideal is far from being 



