DUST AND DISEASE. 323 



rect from the main into the house-tap ; no cisterns are em- 

 ployed, the supply is always fresh and pure. It is highly 

 charged with air. This is the kind of water which is sup- 

 plied to the fortunate people of Tring, Caterham, and Can- 

 terbury. 



Let me, in conclusion, remind you that I do not con- 

 sider the floating matter revealed by the electric beam to be 

 all living matter. I believe that only in exceptional cases, 

 such as those cited in the excellent reports of Dr. Angus 

 Smith, does the quantity of living matter suspended in the 

 air of our streets and rooms amount to more than a small 

 fraction of the total dust. But I believe it to be perfectly 

 well established that, during epidemics, air and water are 

 charged with the specific " materies morbi " by which the 

 disease is spread ; that these two media are, in fact, the 

 chief vehicles of its dissemination. I believe there are the 

 strongest grounds for holding the contagious matter to be 

 " particulate," and further, that the particles are to all in- 

 tents and purposes germs / exhibiting as they do the fun- 

 damental characteristic of propagating their own kind 

 through countless generations, and over vast geographical 

 areas. Their life and reproduction run parallel to, and are 

 an incident of the life of man himself. I do not doubt the 

 ability of these particles to scatter light, nor that the means 

 by which the visible floating dust of our air is arrested, and 

 which demonstrably arrest -with it the germs of various 

 forms of fungoid and animalcular life, including those con- 

 cerned in the phenomena of putrefaction, will also be found 

 effectual in arresting contagium. 



The following extract from a private letter written to 

 me by Dr. William Budd, is so important, and its reasoning 

 is so cleaT, that I asked and obtained the permission of its 

 exceedingly able writer to publish it : 



" Another point of great practical importance is, as far 



