JohnSnowJohnSnow,acreativeLondonphysician,achievedprominenceinthemid-nineteenthcenturyasanobstetricianwhowasamongthefirsttouseanesthesia.Itwashisworkinepidemiology,however,whichearnedhimhispositionasaprototype.Duringthe1830sand1840s,whenseverecholeraepidemicsthreatenedLondon,Dr.Snowhadbecomeinterestedinthecauseandtransmissionofthedisease.In1849,hepublishedabriefpamphlet,OntheModeofCommunicationofCholera,suggestingthatcholeraisacontagiousdiseasecausedbyapoisonthatreproducesinthehumanbodyandisfoundinthevomitusandstoolsofcholerapatients.Hebelievedthatthemain,althoughnotonly,meansoftransmissionwaswatercontaminatedwiththispoison.Thisdifferedfromacommonly-heldtheorythatdiseasesweretransmittedbyinhalationofvapors.Thepamphletcausednogreatstir,andDr.Snow'sargumentwasonlyoneofmanyhopefultheoriesproposedduringatimewhencholerawascausinggreatdistress.Dr.Snowwasabletoprovehistheoryin1854,whenanothersevereepidemicofcholeraoccurredinLondon.Throughpainstakingdocumentationofcholeracasesandcorrelationofthecomparativeincidenceofcholeraamongsubscriberstothecity'stwowatercompanies,heshowedthatcholeraoccurredmuchmorefrequentlyincustomersofonewatercompany,theSouthwarkandVauxhall.ThiscompanydrewitswaterfromthelowerThames,whereithadbecomecontaminatedwithLondonsewage,whereastheothercompanyobtainedwaterfromtheupperThames.Dr.Snow'sevidencesoongainedmanyconverts.用心爱心专心用心爱心专心
