Miasma, μιασμα, this name is derived from the Greek verb which means to soil, to corrupt ; this etymology shows that one must write miasma with an "i" and not with a "y"; this type of spelling is rather common and notably it has slipped into the dictionary in the article Contagion. By miasma is meant extremely subtle bodies that are believed to be the propagators of contagious diseases; people rather naturally thought that these small pieces of prodigiously attenuated material escaped from bodies infected by the disease and communicated it to non-infected people, penetrating their bodies after being spread through the air or more directly, passing immediately from the affected bodies to the non-infected ; it is only by their effects that we have been able suspect their existence; a single man infected by the plague spread this disastrous illness through many countries. When smallpox appears in a town, it is rare that it does not become epidemic; there are times where one sees diseases completely similar in symptoms, incidence, and end results spread throughout a country; if a man in good health drinks from the same glass, wipes himself with the same towels as a person with scabies, or if he merely sleeps next to that person, he rarely fails to contract scabies; there are intense dry patches which are transferred by merely touching; syphilis requires a more immediate touching for propagation, and the application of parts where pores are more open or more present; the nature, suitability, and action of these contagious particles or miasmas are entirely unknown; as they escape our view, we are always reduced to uncertain conjectures on the subject; we cannot conclude otherwise, except that they are bodies which by their delicacy deserve to be looked at as the extremes of immaterial beings, and as placed within the confines that separate matter from abstract beings . See Contagion. And the greater or lesser proximity that different diseases require to be communicated leads to the presumption that their steadiness varies a good deal: some authors have wanted to delve deeper into these mysteries; they claimed to have determined the exact nature of these miasmas , based on the simple observation that the ulcers of plague-stricken people were sprinkled with a large number of worms, an ordinary consequence of corruption; they have not hesitated to call these little animals authors and propagators of the contagion, and they assured us that miasmas were nothing more than these worms that jumped from the bodies of the plague-stricken to those of healthy people, or that spread throughout the air. Desault, a doctor from Bordeaux, having seen the brains of dead, hydrophobic animals filled with worms, concluded from this that hydrophobic miasmas were nothing else; he drew the same conclusion by analogy for venereal disease. Not much effort has been made to refute these opinions because they have had no influence on practice at all; and besides, in similarly obscure cases, all systems have approximately the same degree of probability, and cannot be combatted by evident facts.