491 



of the stomach, be sufficient to cause death, surely the 

 constant application of noxious exudations from a similar 

 source to the large surface of blood in the lungs, will be 

 capable of engendering disease. 



That the moisture condensed from the air of stagnant drains, 

 &c., is sufficient to produce symptoms of putrid fever and death 

 when introduced into the blood of a dog, has been proved by Dr. 

 Southwood Smith, and stated by him in evidence on sanitary 

 matters before a committee of the House of Commons ; and I 

 myself have verified his experiments on other small animals. 

 I therefore believe that it is to this putrefying substance alone 

 that we must look for the causes of all forms of infectious 

 disease, and that it constitutes the various forms of malaria, 

 miasms, &c., which are emitted from putrid marshes, stag- 

 nant drains, and accumulations of filth of every kind. That 

 it is not sulphuretted hydrogen, or any of the ultimate pro- 

 ducts of putrefaction, I think is sufficiently proved by the 

 fact, that persons who conduct processes in which these gases 

 are continually disengaged, and who live in atmospheres 

 highly charged, apparently suflfer no more than persons who 

 visit such places occasionally. These gases are no more 

 capable of producing infectious disease in the human subject, 

 than those which result ultimately from the decomposition of 

 yeast are capable of producing fermentation in a solution of 

 sugar, or those resulting from the decomposition of diastase 

 or emulsin would produce the remarkable transmutation of 

 the elements of starch or amygdalin. If, then, we regard 

 infection as arising from certain decompositions of the 

 animal fluids, induced by the presence of putrid particles 

 dissolved in the respired air, we should naturally expect to 

 find such diseases prevailing to the greatest extent in sheltered 

 valleys or yards, where the air was stagnant, and where such 

 matters were allowed to contaminate the air continually ; and 

 that such is' really the case we have abundant evidence in the 



