STERILIZATION 13 



condition. Pasteur in his early work utilized plaster plates 

 as the filtering medium, but as a result of Chamberland's 

 researches, porous porcelain now supersedes plaster. Finely 

 shredded asbestos packed tightly in a Gooch crucible will 

 serve as a bacterial filter provided the layer of asbestos 

 is sufficiently thick. The rate of filtration is usually very 

 slow because the pores of the filter are so very minute; 

 therefore to overcome this disadvantage either aspiration 

 or pressure is generally employed to hasten the process. 

 This method may not exclude filterable organisms. 



VII. Sterilization by Dialysis. In one of the more 

 recent methods devised for the preparation of antirabic 

 vaccines the vaccine is prepared by placing the virus (spinal 

 cord of a rabid rabbit) in a collodion sac and dialyzing it 

 in running distilled water. The living virus is destroyed, 

 yet its immunizing properties are retained unimpaired. 

 Quite the opposite effect may be obtained under some- 

 what different circumstances. If a collodion sac containing 

 a suspension of a pathogenic organism be placed in the 

 body cavity of a susceptible animal the organisms within 

 the sac thrive, being nourished by the body fluids which 

 diffuse through the semi-permeable membrane. 



GUMMING, J. G.: Rabies Hydrophobia. A study of fixed virus, 

 determination of the M. L. D., vaccine treatment (Hogyes, 

 Pasteur, and dialyzed vaccine), and immunity tests. Journal 

 of Infectious Diseases, Vol. XIV (1914), pp. 33-52. 



VIII. Comminution or the actual crushing of the micro- 

 bial cells is resorted to for demonstrating intracellular 

 enzymes. 



