PUTEEFACTION AND INFECTIOJJ 81 



have been turned to important account in the researches 

 of Dr. Zahn, Professor Klebs, and Dr. Burdon Sander- 

 son. In various instances it has been proved that, as 

 regards the infection of living animals, the porous 

 earthenware intercepts contagia. For the living animal, 

 organic infusions, or Pasteur's solution, may he substi- 

 tuted. Not only are ice-water, distilled water, and 

 tap-water thus deprived of their powers of infection, 

 but, by plunging the porous cell into an infusion swarm- 

 ing with Bacterial life, exhausting the cell, and per- 

 mitting the liquid to be slowly driven through it by 

 atmospheric pressure, the filtrate is not only deprived of 

 its Bacteria, but also of those ultra-microscopic germs 

 which appear to be as potent for infection as the Bac- 

 teria themselves. The precipitated mastic particles 

 before described, which pass unimpeded through an in- 

 definite number of paper filters, are wholly intercepted 

 by the porous cell. 



These germinal particles abound in every pool, 

 stream, and river. All parts of the moist earth are 

 crowded with them. Every wetted surface which has 

 been dried by the sun or air contains upon it the parti- 

 cles which the unevaporated liquid held in suspension. 

 From such surfaces they are detached and wafted away, 

 their universal prevalence in the atmosphere being 

 thus accounted for. Doubtless they sometimes attach 

 themselves to coarser particles, organic and inorganic, 

 which are left behind along with them ; but they need 

 no such rafts to carry them through the air, being them- 

 selves endowed with a power of flotation commensurate 

 with their extreme smallness and the specific lightness 

 of the matter of which they are composed. 



I by no means affirm that the developed Bacterium, 

 which requires for its maintenance nutriment beyond 

 that which ordinary water can always supply, is never 



