^ 304 — 



phosphuretted hydrogen gases and ammonia ; the latter 

 being moreover a rational constituent of the atmos- 

 phere, although in much smaller proportion than car- 

 bonic acid. 



The strongest and most satirfactory evidence of the 

 direct influence of animal matter in a state of putrefac- 

 tive change in producing disease is afforded by the ex- 

 periments of Dr. Angus Smith. He condensed the 

 aqueous vapour from the air of a crowded room by sus-, 

 pending in it, a glass globe filled with ice, and collected 

 the water that trickled from the outer surface of the 

 globe. The condensed fluid soon yielded a deposit, 

 which when allowed to remain a few days at rest, form- 

 ed a solid, thick glutiious mass, having a strong ani- 

 mal odour This deposit, which underwent microsco- 

 pic changes in which were perceived first a vegetable 

 groAvth, followed by the production of multitudes of 

 animalcules, demonstrating clearly that it contained 

 animal matter. '1 his animal matter thrown off' by the 

 lungs and skin of the persons assembled, was found, 

 when thus concentrated, to be a deadly poison, produ- 

 cing head-ache,nausea, or positive disease, according to 

 its degree of concentration. His experiments further 

 show that a few drops of a liquid obtained by the same 

 means from the air of a foul locality, introduced into 

 the veins of a dog, produced death with the usual 

 symptoms of typhus fever. 



Even the malarious emanations from marshes appear 

 to have a similar compos.ition, according to the experi- 

 ments of a continental chemist, who, twenty years ago, 

 condensed the aqueous vapor from the air of marshes 

 in an aqnoish district, and described the condensed li- 

 quid as yielding a deposit similar in appearance and 

 properties to that described by Dr. Angus Smith. 1 

 regret that the name of this chemist has escaped me ; 

 but his results were translated and published in the 

 Lancet, about the period I have mentioned. 



It will be remarked how closely the volatile matters 

 derived from night-soil in my experiments, and the 

 matters obtained from crowded rooms, foul localities, 

 and marshes resemble each other in chemical character 

 and composition. — We are, at present, only on the thre- 



