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re-breathed, are the main cause of the high rate of Phthisis ; 
and, in order to be brief, and at the same time expressive, the 
following conclusions from the late Dr. Parkes may be given. He 
shows that in the badly-ventilated prison of the Leopoldstadt, in 
Vienna, the deaths per rooo prisoners were eighty-six, and out of 
these deaths, 51°4 were due to Phthisis; while, on the other 
hand, in the House of Correction, in the same city, which was 
well-ventilated, the deaths per 1000 were only fourteen, of which 
7°9 were due to Phthisis. From this it is evident that 43% 
per 1000 were distinctly attributable to bad air. 
With regard to what I have grouped as the second source of 
air pollution, namely putrefaction, it may be stated that the results 
of the processes embraced under the comprehensive word of putre- 
faction are gases holding organic substances in suspension, and 
these organic substances are so decidedly distinct from what the 
constituents of the air should be, that when they are well mixed, 
the oxygen or the ozone acts upon them, and converts them 
into inorganic gases. The more ozone present in the air, the 
more rapidly this beneficial change is effected. But the organic 
emanations thus arising from putrefaction are not always simply 
dead forms, but frequently they contain living germs, or organised 
bodies, which directly induce disease, which the atmosphere does 
not readily act upon, and actual investigation has shown that 
they are in many cases the actual nuclei of fresh cases of 
disease. 
The ordinary putrefaction impurities in the atmosphere are 
supposed to be the frequent promoters of disease of the respiratory 
organs, in addition to typhoid and other fevers ; and on looking 
at the statistics of this class of disease throughout the United 
Kingdom, we find that country or agricultural districts are by no 
means exempt from them, and it is a matter of general observation 
that in this particular district the cases of Phthisis, or Consumption, 
are comparatively high. Probably the breathing of air contamin- 
ated with the results of putrefactive changes may be to some extent 
a cause for this. 
Of course the atmosphere, ever fresh and changing in these 
