MODERN IDEAS OF SANITABT ECONOMY. 



61 



compounds, but they themselves are no infection, no zymotic 

 disease. Ammonia, for example, has a great duty to perform; 

 but in excess it exhausts action very much both in living and 

 dead vegetation. 



2. A true gas diffuses itself in the air, or in the gases, but 

 all are soluble to some extent in water. All living bodies 

 contain water; in fact, the motion, mechanical and molecular, 

 necessary to life cannot be carried on without a liquid, nor 

 indeed, generally, can substances act chemically on each other 

 as many substances in the living body do, without the inter- 

 vention of a liquid. Infecting matter is generally connected 

 with diseased moist or liquid bodies, which are always to a 

 certain extent giving off gaseous products in vapour. 



3. Sulphuretted hydrogen, for example, is not miasma; it is 

 deadly enough, but the sources of it are resorted to by invalids, 

 which could not be the case were it a miasma. It may destroy 

 the constitution, and produce other diseases which may have 

 various effects : the same of carbonic acid, &c. Therefore 

 in looking for miasma or infection, we are not to look for 

 chemical compounds, and to decide on the presence of disease 

 from these grounds. From this cause, chemistry has not 

 carried us far in advance of the ancients, who did not know 

 analysis. 



4. The senses are not sufficient to detect miasma. Miasmas 

 do not, at least always, possess a smell, or we are not able to 

 perceive it. We do not smell what we are much accustomed 

 to. In Germany there is the " Englisches Geruch," the smell 

 that all English articles have, a smell of coal, I believe. In 

 some districts every article is found to smell of peat, and this 

 is especially felt on bringing them into a coal district. 



5. The results produced by time, whilst the senses were 

 unconscious and chemical analysis at fault, are to be depended 

 on above all things. For example, bad air may injure im- 

 portant organs ; the senses see the accumulated result. The 

 chemical action is decided and progressive, whilst no pain is 



