236 THE CHEMISTRY OF CREATION. 



of disorders affecting at one time large numbers 

 of persons of all kinds, is equally enveloped 

 in obscurity. A few facts are known, but 

 these are of a sadly insufficient character. 

 Among these is the important and interesting 

 modern discovery, that some diseases, origi- 

 nally local, if they acquired sufficient intensity 

 in the spot where they originate, may pro- 

 ceed, and, gathering additional strength in 

 their progress, eventually become true epi- 

 demics diseases of the people. " Like living 

 things," observes the Registrar-General, " epi- 

 demics do not cease with the circumstances in 

 which they are produced ; they wander to other 

 places, and descend to remoter times." Thus 

 the accumulating filth of a wretched metro- 

 politan alley may be the hot-bed of a disease 

 not confined to the miserable locality, but ex- 

 tending to the broader squares of the wealthy, 

 to the palace doors, and perhaps inner chambers, 

 of the great and noble, and perhaps descending 

 to posterity. As malaria appears to be an 

 atmospheric impurity resulting from vegetable 

 decomposition, so infectious and epidemic dis- 

 orders would seem in most cases to arise from the 

 putrefaction chiefly of animal substances, or in 

 some instances from that of both animal and vege- 

 table materials. 



Reasons exist, to which it is not necessary 



