Justatthecloseofthecenturytherecameintoprominencetheschoolofhomoeopathy，whichwasdestinedtoinfluencethepracticeofmedicineverymateriallyandtooutlivealltheothereighteenth-centuryschools。ItwasfoundedbyChristianSamuelFriedrichHahnemann1755-1843，amostremarkableman，who，afterpropoundingatheoryinhisyoungerdayswhichwasatleastasreasonableasmostoftheexistingtheories，hadthemisfortunetooutlivehisusefulnessandlayhisdoctrineopentoridiculebytheunreasonableteachingsofhisdotage，Hahnemannrejectedalltheteachingsofmorbidanatomyandpathologyasuselessinpractice，andpropoundedhisfamous"similiasimilibuscurantur"——thatalldiseasesweretobecuredbymedicinewhichinhealthproducedsymptomsdynamicallysimilartothediseaseundertreatment。Ifacertainmedicineproducedaheadachewhengiventoahealthyperson，thenthismedicinewasindicatedincaseofheadaches，etc。Atthepresenttimesuchatheoryseemscrudeenough，butinthelatterpartoftheeighteenthcenturyalmostanytheorywasasgoodastheonespropoundedbyAnimists，Vitalists，andothersuchschools。Itcertainlyhadtheverycommendablefeatureofintroducingsimplicityintheuseofdrugsinplaceofthecomplicatedprescriptionstheninvogue。HadHahnemannstoppedatthispointhecouldnothavebeenhelduptotheindefensibleridiculethatwasbroughtuponhim，withconsiderablejustice，byhislatertheories。Buthelivedontopropoundhisextraordinarytheoryof"potentiality"——thatmedicinesgainedstrengthbybeingdiluted——andhisevenmoreextraordinarytheorythatallchronicdiseasesarecausedeitherbytheitch，syphilis，orfig-wartdisease，orarebroughtonbymedicines。
　　Atthetimethathistheoryofpotentialitieswaspromulgated，themedicalworldhadgonemadinitsadministrationofhugedosesofcompoundmixturesofdrugs，andanyreactionagainstthiswassurelyanimprovement。Inshort，nomedicineatallwasmuchbetterthantheheapingdosesusedincommonpractice；andhenceoneadvantage，atleast，ofHahnemann’smethods。Statedbriefly，histheorywasthatifatincturebereducedtoone-fiftiethinstrength，andthisagainreducedtoone-fiftieth，andthisprocessrepeateduptothirtysuchdilutions，thepotencyofsuchamedicinewillbeincreasedbyeachdilution，Hahnemannhimselfpreferringtheweakest，or，ashewouldcallit，thestrongestdilution。Theabsurdityofsuchatheoryisapparentwhenitisunderstoodthatlongbeforeanydrughasbeenraisedtoitsthirtiethdilutionithasbeensoreducedinquantitythatitcannotbeweighed，measured，orrecognizedasbeingpresentinthesolutionatallbyanymeansknowntochemists。Itisbutjusttomodernfollowersofhomoeopathytosaythatwhilemostofthemadvocatesmalldosage，theydonotnecessarilyfollowtheteachingsofHahnemanninthisrespect，believingthatthetheoryofthedose"hasnothingmoretodowiththeoriginallawofcurethanthepsoraitchtheoryhas；
　　andthatitwasoneofthelatercreationsofHahnemann’smind。"
　　Hahnemann’stheorythatallchronicdiseasesarederivedfromeitheritch，syphilis，orfig-wartdiseaseisnolongeradvocatedbyhisfollowers，becauseitissoeasilydisproved，particularlyinthecaseofitch。Hahnemanntaughtthatfullythree-quartersofalldiseaseswerecausedby"itchstruckin，"andyetithadbeendemonstratedlongbeforehisday，andcanbedemonstratedanytime，thatitchissimplyalocalskindiseasecausedbyasmallparasite。
　　JENNERANDVACCINATION
　　Alladvancesinsciencehaveabearing，nearorremote，onthewelfareofourrace；butitremainstocredittotheclosingdecadeoftheeighteenthcenturyadiscoverywhich，initspowerofdirectandimmediatebenefittohumanity，surpassesanyotherdiscoveryofthisoranypreviousepoch。Needlesstosay，IrefertoJenner’sdiscoveryofthemethodofpreventingsmallpoxbyinoculationwiththevirusofcow-pox。ItdetractsnothingfromthemeritofthisdiscoverytosaythatthepreventivepowerofaccidentalinoculationhadlongbeenrumoredamongthepeasantryofEngland。Suchvague，unavailinghalf-knowledgeisoftentheforerunneroffruitfuldiscovery。
　　ToallintentsandpurposesJenner’sdiscoverywasoriginalandunique。Nor，consideredasaperfectmethod，wasitinanysenseanaccident。Itwasatriumphofexperimentalscience。Thediscovererwasnonoviceinscientificinvestigation，butatrainedobserver，whohadservedalongapprenticeshipinscientificobservationundernolessascientistthanthecelebratedJohnHunter。Attheageoftwenty-oneJennerhadgonetoLondontopursuehismedicalstudies，andsoonafterheprovedhimselfsoworthyapupilthatfortwoyearsheremainedamemberofHunter’shouseholdashisfavoritepupil。HistasteforscienceandnaturalhistorysoonattractedtheattentionofSirJosephBanks，whointrustedhimwiththepreparationofthezoologicalspecimensbroughtbackbyCaptainCook’sexpeditionin1771。Heperformedthistasksowellthathewasofferedthepositionofnaturalisttothesecondexpedition，butdeclinedit，preferringtotakeupthepracticeofhisprofessioninhisnativetownofBerkeley。
　　Hismanyaccomplishmentsandgenialpersonalitysoonmadehimafavoritebothasaphysicianandinsociety。Hewasagoodsinger，afairviolinistandflute-player，andaverysuccessfulwriterofproseandverse。Butwithallhisprofessionalandsocialdutieshestillkeptuphisscientificinvestigations，amongotherthingsmakingsomecarefulobservationsonthehibernationofhedgehogsattheinstigationofHunter，theresultsofwhichwerelaidbeforetheRoyalSociety。Healsomadequiteextensiveinvestigationsastothegeologicalformationsandfossilsfoundinhisneighborhood。
　　EvenduringhisstudentdayswithHunterhehadbeenmuchinterestedinthebelief，currentintheruraldistrictsofGloucestershire，oftheantagonismbetweencow-poxandsmall-pox，apersonhavingsufferedfromcow-poxbeingimmunedtosmall-pox。
　　AtvarioustimesJennerhadmentionedthesubjecttoHunter，andhewasconstantlymakinginquiriesofhisfellow-practitionersastotheirobservationsandopinionsonthesubject。Hunterwastoofullyengrossedinotherpursuitstogivethemattermuchseriousattention，however，andJenner’sbrothersoftheprofessiongavescantcredencetotherumors，althoughsuchrumorswerecommonenough。
　　Atthistimethepracticeofinoculationforpreventingsmall-pox，orratheravertingthesevererformsofthedisease，waswidelypractised。Itwascustomary，whentherewasamildcaseofthedisease，totakesomeofthevirusfromthepatientandinoculatepersonswhohadneverhadthedisease，producingasimilarattackinthem。Unfortunatelythereweremanyobjectionstothispractice。Theinoculatedpatientfrequentlydevelopedavirulentformofthediseaseanddied；orifherecovered，evenafteramildattack，hewaslikelytobe"pitted"anddisfigured。
　　But，perhapsworstofall，apatientsoinoculatedbecamethesourceofinfectiontoothers，anditsometimeshappenedthatdisastrousepidemicswerethusbroughtabout。Thecasewasamostperplexingone，fortheawfulscourgeofsmall-poxhungperpetuallyovertheheadofeverypersonwhohadnotalreadysufferedandrecoveredfromit。ThepracticeofinoculationwasintroducedintoEnglandbyLadyMaryWortleyMontague1690-1762，whohadseenitpractisedintheEast，andwhoannouncedherintentionof"introducingitintoEnglandinspiteofthedoctors。"
　　Fromthefactthatcertainpersons，usuallymilkmaids，whohadsufferedfromcow-poxseemedtobeimmunedtosmall-pox，itwouldseemaverysimpleprocessofdeductiontodiscoverthatcow-poxinoculationwasthesolutionoftheproblemofpreventingthedisease。Buttherewasanotherformofdiseasewhich，whilecloselyresemblingcow-poxandquitegenerallyconfoundedwithit，didnotproduceimmunity。Theconfusionofthesetwoformsofthediseasehadconstantlymisledinvestigationsastothepossibilityofeitherofthemimmunizingagainstsmallpox，andtheconfusionofthesetwodiseasesforatimeledJennertoquestionthepossibilityofdoingso。Aftercarefulinvestigations，however，hereachedtheconclusionthattherewasadifferenceintheeffectsofthetwodiseases，onlyoneofwhichproducedimmunityfromsmall-pox。
　　"Thereisadiseasetowhichthehorse，fromhisstateofdomestication，isfrequentlysubject，"wroteJenner，inhisfamouspaperonvaccination。"Thefarrierscallitthegrease。
　　Itisaninflammationandswellingintheheel，accompaniedatitscommencementwithsmallcracksorfissures，fromwhichissuesalimpidfluidpossessingpropertiesofaverypeculiarkind。
　　ThisfluidseemscapableofgeneratingadiseaseinthehumanbodyafterithasundergonethemodificationIshallpresentlyspeakofwhichbearssostrongaresemblancetosmall-poxthatI
　　thinkithighlyprobableitmaybethesourceofthatdisease。
　　"Inthisdairycountryagreatnumberofcowsarekept，andtheofficeofmilkingisperformedindiscriminatelybymenandmaidservants。OneoftheformerhavingbeenappointedtoapplydressingstotheheelsofahorseaffectedwiththemaladyIhavementioned，andnotpayingdueattentiontocleanliness，incautiouslybearshispartinmilkingthecowswithsomeparticlesoftheinfectiousmatteradheringtohisfingers。Whenthisisthecaseitfrequentlyhappensthatadiseaseiscommunicatedtothecows，andfromthecowstothedairy-maids，whichspreadsthroughthefarmuntilmostofthecattleanddomesticsfeelitsunpleasantconsequences。ThisdiseasehasobtainedthenameofCow-Pox。Itappearsonthenipplesofthecowsintheformofirregularpustules。Attheirfirstappearancetheyarecommonlyofapalishblue，orratherofacolorsomewhatapproachingtolivid，andaresurroundedbyaninflammation。
　　Thesepustules，unlessatimelyremedybeapplied，frequentlydegenerateintophagedeniculcers，whichproveextremelytroublesome。Theanimalsbecomeindisposed，andthesecretionofmilkismuchlessened。Inflamedspotsnowbegintoappearondifferentpartsofthehandsofthedomesticsemployedinmilking，andsometimesonthewrists，whichrunontosuppuration，firstassumingtheappearanceofthesmallvesicationsproducedbyaburn。Mostcommonlytheyappearaboutthejointsofthefingersandattheirextremities；butwhateverpartsareaffected，ifthesituationwilladmitthesuperficialsuppurationsputonacircularformwiththeiredgesmoreelevatedthantheircentreandofacolordistinctlyapproachingtoblue。Absorptiontakesplace，andtumorsappearineachaxilla。Thesystembecomesaffected，thepulseisquickened；
　　shiverings，succeededbyheat，generallassitude，andpainsabouttheloinsandlimbs，withvomiting，comeon。Theheadispainful，andthepatientisnowandthenevenaffectedwithdelirium。Thesesymptoms，varyingintheirdegreesofviolence，generallycontinuefromonedaytothreeorfour，leavingulceratedsoresaboutthehandswhich，fromthesensibilityoftheparts，areverytroublesomeandcommonlyhealslowly，frequentlybecomingphagedenic，likethosefromwhichtheysprang。Duringtheprogressofthediseasethelips，nostrils，eyelids，andotherpartsofthebodyaresometimesaffectedwithsores；buttheseevidentlyarisefromtheirbeingheedlesslyrubbedorscratchedbythepatient’sinfectedfingers。Noeruptionsontheskinhavefollowedthedeclineofthefeverishsymptomsinanyinstancethathascomeundermyinspection，oneonlyexcepted，andinthiscaseaveryfewappearedonthearms:
　　theywereveryminute，ofavividredcolor，andsoondiedawaywithoutadvancingtomaturation，sothatIcannotdeterminewhethertheyhadanyconnectionwiththeprecedingsymptoms。
　　"ThusthediseasemakesitsprogressfromthehorseasI
　　conceivetothenippleofthecow，andfromthecowtothehumansubject。
　　"Morbidmatterofvariouskinds，whenabsorbedintothesystem，mayproduceeffectsinsomedegreesimilar；butwhatrendersthecow-poxvirussoextremelysingularisthatthepersonthathasbeenthusaffectedisforeveraftersecurefromtheinfectionofsmall-pox，neitherexposuretothevariolouseffluvianortheinsertionofthematterintotheskinproducingthisdistemper。"[2]
　　In1796Jennermadehisfirstinoculationwithcowpoxmatter，andtwomonthslaterthesamesubjectwasinoculatedwithsmall-poxmatter。But，asJennerhadpredicted，noattackofsmall-poxfollowed。Althoughfullyconvincedbythisexperimentthatthecasewasconclusivelyproven，hecontinuedhisinvestigations，waitingtwoyearsbeforepublishinghisdiscovery。Then，fortifiedbyindisputableproofs，hegaveittotheworld。Theimmediateeffectsofhisannouncementhaveprobablyneverbeenequalledinthehistoryofscientificdiscovery，unless，perhaps，inthesingleinstanceofthediscoveryofanaesthesia。InGenevaandHollandclergymenadvocatedthepracticeofvaccinationfromtheirpulpits；insomeoftheLatincountriesreligiousprocessionswereformedforreceivingvaccination；Jenner’sbirthdaywascelebratedasafeastinGermany；andthefirstchildvaccinatedinRussiawasnamed"Vaccinov"andeducatedatpublicexpense。Insixyearsthediscoveryhadpenetratedtothemostremotecornersofcivilization；ithadevenreachedsomesavagenations。Andinafewyearssmall-poxhadfallenfromthepositionofthemostdreadedofalldiseasestothatofbeingpracticallytheonlydiseaseforwhichasureandeasypreventivewasknown。
　　HonorswereshowereduponJennerfromtheOldandtheNewWorld，andevenNapoleon，thebitterhateroftheEnglish，wasamongtheotherswhohonoredhisname。OnoneoccasionJennerappliedtotheEmperorforthereleaseofcertainEnglishmendetainedinFrance。Thepetitionwasabouttoberejectedwhenthenameofthepetitionerwasmentioned。"Ah，"saidNapoleon，"wecanrefusenothingtothatname！"
　　Itisdifficultforusofto-dayclearlytoconceivethegreatnessofJenner’striumph，forwecanonlyvaguelyrealizewhataruthlessandever-presentscourgesmallpoxhadbeentoallpreviousgenerationsofmensincehistorybegan。Despitealleffortstocheckitbymedicationandbydirectinoculation，itsweptnowandthenovertheearthasanall-devastatingpestilence，andyearbyyearitclaimedone-tenthofallthebeingsinChristendombydeathasitsaveragequotaofvictims。
　　"Fromsmall-poxandlovebutfewremainfree，"rantheoldsaw。A
　　pittedfacewasalmostasmuchamatterofcourseahundredyearsagoasasmoothoneisto-day。
　　Littlewonder，then，thattheworldgaveeageracceptancetoJenner’sdiscovery。Nourgingwasneededtoinducethemajoritytogiveittrial；passengersonaburningshipdonotholdalooffromthelife-boats。Richandpoor，highandlow，soughtsuccorinvaccinationandblessedthenameoftheirdeliverer。Ofallthegreatnamesthatwerebeforetheworldintheclosingdaysofthecentury，therewasperhapsnootheroneatoncesowidelyknownandsouniformlyreverencedasthatofthegreatEnglishphysicianEdwardJenner。Surelytherewasnootheronethatshouldberecalledwithgreatergratitudebyposterity。
　　VIII。NINETEENTH-CENTURYMEDICINE
　　PHYSICALDIAGNOSIS
　　AlthoughNapoleonBonaparte，FirstConsul，wasnotlackinginself-appreciation，heprobablydidnotrealizethatinselectingaphysicianforhisownneedshewasmarkedlyinfluencingtheprogressofmedicalscienceasawhole。YetsostrangelyarecauseandeffectadjustedinhumanaffairsthatthissimpleactoftheFirstConsulhadthatveryunexpectedeffect。Forthemanchosenwastheenvoyofanewmethodinmedicalpractice，andthefamewhichcametohimthroughbeingphysiciantotheFirstConsul，andsubsequentlytotheEmperor，enabledhimtopromulgatethemethodinawayotherwiseimpracticable。HencetheindirectbuttellingvaluetomedicalscienceofNapoleon’sselection。
　　ThephysicianinquestionwasJeanNicolasdeCorvisart。Hisnovelmethodwasnothingmorestartlingthanthenow-familiarprocedureoftappingthechestofapatienttoelicitsoundsindicativeofdiseasedtissueswithin。Everyonehasseenthisdonecommonlyenoughinourday，butatthebeginningofthecenturyCorvisart，andperhapssomeofhispupils，wereprobablytheonlyphysiciansintheworldwhoresortedtothissimpleandusefulprocedure。HenceNapoleon’ssurprisewhen，oncallinginCorvisart，afterbecomingsomewhatdissatisfiedwithhisotherphysiciansPinelandPortal，hisphysicalconditionwasinterrogatedinthisstrangemanner。WithcharacteristicshrewdnessBonapartesawtheutilityofthemethod，andthephysicianwhothusattemptedtosubstitutescientificmethodforguess-workinthediagnosisofdiseaseatoncefoundfavorinhiseyesandwasinstalledashisregularmedicaladviser。
　　ForfifteenyearsbeforethisCorvisarthadpractisedpercussion，asthechest-tappingmethodiscalled，withoutsucceedinginconvincingtheprofessionofitsvalue。Themethoditself，itshouldbeadded，hadnotoriginatedwithCorvisart，nordidtheFrenchphysicianforamomentclaimitashisown。ThetrueoriginatorofthepracticewastheGermanphysicianAvenbrugger，whopublishedabookaboutitasearlyas1761。ThisbookhadevenbeentranslatedintoFrench，thenthelanguageofinternationalcommunicationeverywhere，byRozieredelaChassagne，ofMontpellier，in1770；butnooneotherthanCorvisartappearstohavepaidanyattentiontoeitheroriginalortranslation。Itwasfarotherwise，however，whenCorvisarttranslatedAvenbrugger’sworkanew，withimportantadditionsofhisown，in1808。
　　"Iknowverywellhowlittlereputationisallottedtotranslatorandcommentators，"writesCorvisart，"andImighteasilyhaveelevatedmyselftotherankofanauthorifIhadelaboratedanewthedoctrineofAvenbruggerandpublishedanindependentworkonpercussion。Inthisway，however，IshouldhavesacrificedthenameofAvenbruggertomyownvanity，athingwhichIamunwillingtodo。Itishe，andthebeautifulinventionwhichofrightbelongstohim，thatIdesiretorecalltolife。"[1]
　　Bythistimeareactionhadsetinagainstthemetaphysicalmethodsinmedicinethathadpreviouslybeensoalluring；thescientificspiritofthetimewasmakingitselffeltinmedicalpractice；andthis，combinedwithCorvisart’sfame，broughtthemethodofpercussionintoimmediateandwell-deservedpopularity。
　　Thuswaslaidthefoundationforthemethodofso-calledphysicaldiagnosis，whichisoneofthecorner-stonesofmodernmedicine。
　　Themethodofphysicaldiagnosisaspractisedinourdaywasbynomeanscompleted，however，withtheworkofCorvisart。
　　Percussionalonetellsmuchlessthanhalfthestorythatmaybeelicitedfromtheorgansofthechestbyproperinterrogation。
　　Theremainderofthestorycanonlybelearnedbyapplyingtheearitselftothechest，directlyorindirectly。Simpleasthisseems，noonethoughtofpractisingitforsomeyearsafterCorvisarthadshownthevalueofpercussion。
　　Then，in1815，anotherParisphysician，ReneTheophileHyacintheLaennec，discovered，almostbyaccident，thatthesoundoftheheart-beatcouldbeheardsurprisinglythroughacylinderofpaperheldtotheearandagainstthepatient’schest。Actingonthehintthusreceived，Laennecsubstitutedahollowcylinderofwoodforthepaper，andfoundhimselfprovidedwithaninstrumentthroughwhichnotmerelyheartsoundsbutmurmursofthelungsinrespirationcouldbeheardwithalmoststartlingdistinctness。
　　ThepossibilityofassociatingthevaryingchestsoundswithdiseasedconditionsoftheorganswithinappealedtothefertilemindofLaennecasopeningnewvistasintherapeutics，whichhedeterminedtoentertothefullestextentpracticable。HisconnectionwiththehospitalsofParisgavehimfullopportunityinthisdirection，andhislaborsofthenextfewyearsservednotmerelytoestablishthevalueofthenewmethodasanaidtodiagnosis，butlaidthefoundationalsoforthescienceofmorbidanatomy。In1819LaennecpublishedtheresultsofhislaborsinaworkcalledTraited’AuscultationMediate，[2]aworkwhichformsoneofthelandmarksofscientificmedicine。Bymediateauscultationismeant，ofcourse，theinterrogationofthechestwiththeaidofthelittleinstrumentalreadyreferredto，aninstrumentwhichitsoriginatorthoughthardlyworthnaminguntilvariousbarbarousappellationswereappliedtoitbyothers，afterwhichLaennecdecidedtocallitthestethoscope，anamewhichithaseversinceretained。
　　Insubsequentyearstheformofthestethoscope，asusuallyemployed，wasmodifiedanditsvalueaugmentedbyabinauricularattachment，andinveryrecentyearsafurtherimprovementhasbeenmadethroughapplicationoftheprincipleofthetelephone；
　　buttheessentialsofauscultationwiththestethoscopewereestablishedinmuchdetailbyLaennec，andthehonormustalwaysbehisofthustakingoneofthelongestsinglestepsbywhichpracticalmedicinehasinourcenturyacquiredtherighttobeconsideredarationalscience。Laennec’seffortscosthimhislife，forhediedin1826ofalungdiseaseacquiredinthecourseofhishospitalpractice；butevenbeforethishisfamewasuniversal，andthevalueofhismethodhadbeenrecognizedallovertheworld。Notlongafter，in1828，yetanotherFrenchphysician，Piorry，perfectedthemethodofpercussionbyintroducingthecustomoftapping，notthechestdirectly，butthefingerorasmallmetalorhard-rubberplateheldagainstthechest-mediatepercussion，inshort。Thisperfectedthemethodsofphysicaldiagnosisofdiseasesofthechestinallessentials；
　　andfromthatdaytillthispercussionandauscultationhaveheldanunquestionedplaceintheregulararmamentariumofthephysician。
　　Coupledwiththenewmethodofphysicaldiagnosisintheefforttosubstituteknowledgeforguess-workcamethestudiesoftheexperimentalphysiologists——inparticular，MarshallHallinEnglandandFrancoisMagendieinFrance；andthejointeffortsofthesevariousworkersledpresentlytotheabandonmentofthosesevereandoftenirrationaldepletivemethods——blood-lettingandthelike——thathadpreviouslydominatedmedicalpractice。Tothisendalsothe"statisticalmethod，"introducedbyLouisandhisfollowers，largelycontributed；andbythecloseofthefirstthirdofourcenturytheideawasgaininggroundthattheprovinceoftherapeuticsistoaidnatureincombatingdisease，andthatthismayoftenbeaccomplishedbetterbysimplemeansthanbytheheroicmeasureshithertothoughtnecessary。Inaword，scientificempiricismwasbeginningtogainahearinginmedicineasagainstthemetaphysicalpreconceptionsoftheearliergenerations。
　　PARASITICDISEASES
　　IhavejustadvertedtothefactthatNapoleonBonaparte，asFirstConsulandasEmperor，wasthevictimofamaladywhichcausedhimtoseektheadviceofthemostdistinguishedphysiciansofParis。Itisalittleshockingtomodernsensibilitiestoreadthatthesephysicians，exceptCorvisart，diagnosedthedistinguishedpatient’smaladyas"galerepercutee"——thatistosay，inidiomaticEnglish，theitch"struckin。"Itishardlynecessarytosaythatnophysicianoftodaywouldmakesoinconsiderateadiagnosisinthecaseofaroyalpatient。Ifbyanychanceadistinguishedpatientwereafflictedwiththeitch，thesagaciousphysicianwouldcarefullyhidethefactbehindcircumlocutionsandproceedtoeradicatethediseasewithalldespatch。ThatthephysiciansofNapoleondidotherwiseisevidencethatatthebeginningofthecenturythediseaseinquestionenjoyedaverydifferentstatus。Atthattimeitch，insteadofbeingamostplebeianmalady，was，sotosay，acourtdisease。Itenjoyedacirculation，inhighcirclesandinlow，thatmoderntherapeuticshasquitedeniedit；andthephysiciansofthetimegaveitafictitiousaddedimportancebyascribingtoitsinfluencetheexistenceofalmostanyobscuremaladythatcameundertheirobservation。LongafterNapoleon’stimegalecontinuedtoholdthisprouddistinction。Forexample，theimaginativeDr。Hahnemanndidnothesitatetoaffirm，asapositivemaxim，thatthree-fourthsofalltheillsthatfleshisheirtowereinrealitynothingbutvariousformsof"galerepercutee。"
　　Allofwhichgoestoshowhoweasyitmaybeforamaskedpretendertoimposeoncreduloushumanity，fornothingismoreclearlyestablishedinmodernknowledgethanthefactthat"galerepercutee"wassimplyanametohideaprofoundignorance；nosuchdiseaseexistsoreverdidexist。Galeitselfisasufficientlytangiblereality，tobesure，butitisapurelylocaldiseaseoftheskin，duetoaperfectlydefinitecause，andthedireinternalconditionsformerlyascribedtoithavereallynocausalconnectionwithitwhatever。Thisdefinitecause，aseveryonenowadaysknows，isnothingmoreorlessthanamicroscopicinsectwhichhasfoundlodgmentontheskin，andhasburrowedandmadeitselfathomethere。Killthatinsectandthediseaseisnomore；henceithascometobeanaxiomwiththemodernphysicianthattheitchisoneofthethreeorfourdiseasesthathepositivelyisabletocure，andthatveryspeedily。Butitwasfarotherwisewiththephysiciansofthefirstthirdofourcentury，becausetothemthecauseofthediseasewasanabsolutemystery。
　　Itistruethathereandthereaphysicianhadclaimedtofindaninsectlodgedintheskinofasuffererfromitch，andtwoorthreetimestheclaimhadbeenmadethatthiswasthecauseofthemalady，butsuchviewswerequiteignoredbythegeneralprofession，andin1833itwasstatedinanauthoritativemedicaltreatisethatthe"causeofgaleisabsolutelyunknown。"Butevenatthistime，asitcuriouslyhappened，therewerecertainignorantlaymenwhohadattainedtoabitofmedicalknowledgethatwaswithheldfromtheinnercirclesoftheprofession。AsthepeasantryofEnglandbeforeJennerhadknownofthecurativevalueofcow-poxoversmall-pox，sothepeasantwomenofPolandhadlearnedthattheannoyingskindiseasefromwhichtheysufferedwascausedbyanalmostinvisibleinsect，and，furthermore，hadacquiredthetrickofdislodgingthepestiferouslittlecreaturewiththepointofaneedle。Fromthemayouthofthecountry，F。Renuccibyname，learnedtheopensecret。HeconveyedittoPariswhenhewenttheretostudymedicine，andin1834demonstratedittohismasterAlibert。Thisphysician，atfirstsceptical，soonwasconvinced，andgaveoutthediscoverytothemedicalworldwithanauthoritythatledtoearlyacceptance。
　　Nowtheimportanceofallthis，inthepresentconnection，isnotatallthatitgavetheclewtothemethodofcureofasingledisease。Whatmakesthediscoveryepochalisthefactthatitdroppedabrand-newideaintothemedicalranks——anideadestined，inthelong-run，toproveitselfaveritablebomb——theidea，namely，thataminuteandquiteunsuspectedanimalparasitemaybethecauseofawell-known，widelyprevalent，andimportanthumandisease。Ofcoursethefullforceofthisideacouldonlybeappreciatedinthelightoflaterknowledge；butevenatthetimeofitscomingitsufficedtogiveagreatimpetustothatnewmedicalknowledge，basedonmicroscopicalstudies，whichhadbutrecentlybeenmadeaccessiblebytheinventionsofthelens-makers。Thenewknowledgeclarifiedoneveryturbidmedicalpoolandpointedthewaytotheclarificationofmanyothers。
　　AlmostatthesametimethatthePolishmedicalstudentwasdemonstratingtheitchmiteinParis，itchanced，curiouslyenough，thatanothermedicalstudent，thistimeanEnglishman，madeananalogousdiscoveryofperhapsevengreaterimportance。
　　Indeed，thisEnglishdiscoveryinitsinitialstagesslightlyantedatedtheother，foritwasin1833thatthestudentinquestion，JamesPaget，interneinSt。Bartholomew’sHospital，London，whiledissectingthemusculartissuesofahumansubject，foundlittlespecksofextraneousmatter，which，whentakentotheprofessorofcomparativeanatomy，RichardOwen，wereascertained，withtheaidofthemicroscope，tobethecocoonofaminuteandhithertounknowninsect。OwennamedtheinsectTrichinaspiralis。Afterthediscoverywaspublishedittranspiredthatsimilarspeckshadbeenobservedbyseveralearlierinvestigators，butnoonehadpreviouslysuspectedor，atanyrate，demonstratedtheirnature。NorwasthefullstoryofthetrichinamadeoutforalongtimeafterOwen’sdiscovery。Itwasnottill1847thattheAmericananatomistDr。JosephLeidyfoundthecystsoftrichinainthetissuesofpork；andanotherdecadeorsoelapsedafterthatbeforeGermanworkers，chiefamongwhomwereLeuckart，Virchow，andZenker，provedthattheparasitegetsintothehumansystemthroughingestionofinfectedpork，andthatitcausesadefinitesetofsymptomsofdiseasewhichhithertohadbeenmistakenforrheumatism，typhoidfever，andothermaladies。Thenthemedicalworldwasagogforatimeoverthesubjectoftrichinosis；governmentinspectionofporkwasestablishedinsomepartsofGermany；AmericanporkwasexcludedaltogetherfromFrance；andthewholesubjectthuscameprominentlytopublicattention。Butimportantasthetrichinaparasiteprovedonitsownaccountintheend，itsgreatestimportance，afterall，wasintheshareitplayedindirectingattentionatthetimeofitsdiscoveryin1833tothesubjectofmicroscopicparasitesingeneral。
　　Thedecadethatfollowedthatdiscoverywasatimeofgreatactivityinthestudyofmicroscopicorganismsandmicroscopictissues，andsuchmenasEhrenbergandHenleandBorySaint-VincentandKollikerandRokitanskyandRemakandDujardinwerewideningtheboundsofknowledgeofthisnewsubjectwithdetailsthatcannotbemorethanreferredtohere。ButthecrowningachievementoftheperiodinthisdirectionwasthediscoverymadebytheGerman，J。L。Schoenlein，in1839，thataverycommonandmostdistressingdiseaseofthescalp，knownasfavus，isreallyduetothepresenceandgrowthonthescalpofavegetableorganismofmicroscopicsize。Thusitwasmadeclearthatnotmerelyanimalbutalsovegetableorganismsofobscure，microscopicspecieshavecausalrelationstothediseaseswithwhichmankindisafflicted。Thisknowledgeoftheparasiteswasanotherlongstepinthedirectionofscientificmedicalknowledge；buttheheightstowhichthisknowledgeledwerenottobescaled，orevenrecognized，untilanothergenerationofworkershadenteredthefield。
　　PAINLESSSURGERY
　　Meantime，inquiteanotherfieldofmedicine，eventsweredevelopingwhichledpresentlytoarevelationofgreaterimmediateimportancetohumanitythananyotherdiscoverythathadcomeinthecentury，perhapsinanyfieldofsciencewhatever。Thiswasthediscoveryofthepain-dispellingpowerofthevaporofsulphuricetherinhaledbyapatientundergoingasurgicaloperation。ThisdiscoverycamesolelyoutofAmerica，anditstandscuriouslyisolated，sinceapparentlynomindsinanyothercountryweretrendingtowardsitevenvaguely。Davy，inEngland，hadindeedoriginatedthemethodofmedicationbyinhalation，andearnedoutsomemostinterestingexperimentsfiftyyearsearlier，anditwasdoubtlesshisexperimentswithnitrousoxidegasthatgavetheclewtooneoftheAmericaninvestigators；butthiswasthesolecontributionofprecedinggenerationstothesubject，andsincethebeginningofthecentury，whenDavyturnedhisattentiontoothermatters，noonehadmadetheslightestadvancealongthesamelineuntilanAmericandentistrenewedtheinvestigation。
　　Inviewofthesequel，Davy’sexperimentsmeritfullattention。
　　Hereishisownaccountofthem，aswrittenin1799:
　　"Immediatelyafterajourneyofonehundredandtwenty-sixmiles，inwhichIhadnosleeptheprecedingnight，beingmuchexhausted，Irespiredsevenquartsofnitrousoxidegasfornearthreeminutes。Itproducedtheusualpleasurableeffectsandslightmuscularmotion。Icontinuedexhilaratedforsomeminutesafterwards，butinhalfanhourfoundmyselfneithermorenorlessexhaustedthanbeforetheexperiment。Ihadagreatpropensitytosleep。
　　"Toascertainwithcertaintywhetherthemoreextensiveactionofnitrousoxidecompatiblewithlifewascapableofproducingdebility，Iresolvedtobreathethegasforsuchatime，andinsuchquantities，astoproduceexcitementequalindurationandsuperiorinintensitytothatoccasionedbyhighintoxicationfromopiumoralcohol。
　　"Tohabituatemyselftotheexcitement，andtocarryitongradually，onDecember26thIwasenclosedinanair-tightbreathing-box，ofthecapacityofaboutnineandone-halfcubicfeet，inthepresenceofDr。Kinglake。AfterIhadtakenasituationinwhichIcouldbymeansofacurvedthermometerinsertedunderthearm，andastop-watch，ascertainthealterationsinmypulseandanimalheat，twentyquartsofnitrousoxidewerethrownintothebox。
　　"ForthreeminutesIexperiencednoalterationinmysensations，thoughimmediatelyaftertheintroductionofthenitrousoxidethesmellandtasteofitwereveryevident。InfourminutesI
　　begantofeelaslightglowinthecheeksandagenerallydiffusedwarmthoverthechest，thoughthetemperatureoftheboxwasnotquite50degrees……Intwenty-fiveminutestheanimalheatwas100degrees，pulse124。Inthirtyminutestwentyquartsmoreofgaswereintroduced。
　　"Mysensationswerenowpleasant；Ihadagenerallydiffusedwarmthwithouttheslightestmoistureoftheskin，asenseofexhilarationsimilartothatproducedbyasmalldoseofwine，andadispositiontomuscularmotionandtomerriment。
　　"Inthree-quartersofanhourthepulsewas104andtheanimalheatnot99。5degrees，thetemperatureofthechamber64degrees。
　　Thepleasurablefeelingscontinuedtoincrease，thepulsebecamefullerandslower，tillinaboutanhouritwas88，whentheanimalheatwas99degrees。Twentyquartsmoreofairwereadmitted。Ihadnowagreatdispositiontolaugh，luminouspointsseemedfrequentlytopassbeforemyeyes，myhearingwascertainlymoreacute，andIfeltapleasantlightnessandpowerofexertioninmymuscles。Inashorttimethesymptomsbecamestationary；breathingwasratheroppressed，andonaccountofthegreatdesireforactionrestwaspainful。
　　"Inowcameoutofthebox，havingbeeninpreciselyanhourandaquarter。ThemomentafterIbegantorespiretwentyquartsofunminglednitrousoxide。Athrillingextendingfromthechesttotheextremitieswasalmostimmediatelyproduced。Ifeltasenseoftangibleextensionhighlypleasurableineverylimb；myvisibleimpressionsweredazzlingandapparentlymagnified，I
　　hearddistinctlyeverysoundintheroom，andwasperfectlyawareofmysituation。Bydegrees，asthepleasurablesensationsincreased，Ilostallconnectionwithexternalthings；trainsofvividvisibleimagesrapidlypassedthroughmymindandwereconnectedwithwordsinsuchamannerastoproduceperceptionsperfectlynovel。
　　"Iexistedinaworldofnewlyconnectedandnewlymodifiedideas。Itheorized；IimaginedthatImadediscoveries。WhenI
　　wasawakenedfromthissemi-delirioustrancebyDr。Kinglake，whotookthebagfrommymouth，indignationandpridewerethefirstfeelingsproducedbythesightofpersonsaboutme。Myemotionswereenthusiasticandsublime；andforaminuteIwalkedabouttheroomperfectlyregardlessofwhatwassaidtome。AsI
　　recoveredmyformerstateofmind，IfeltaninclinationtocommunicatethediscoveriesIhadmadeduringtheexperiment。I
　　endeavoredtorecalltheideas——theywerefeebleandindistinct；
　　onecollectionofterms，however，presenteditself，and，withmostintensebeliefandpropheticmanner，IexclaimedtoDr。
　　Kinglake，’Nothingexistsbutthoughts！——theuniverseiscomposedofimpressions，ideas，pleasures，andpains。’"[3]
　　FromthisaccountweseethatDavyhasanaesthetizedhimselftoapointwhereconsciousnessofsurroundingswaslost，butnotpastthestageofexhilaration。HadDr。Kinglakeallowedtheinhaling-bagtoremaininDavy’smouthforafewmomentslongercompleteinsensibilitywouldhavefollowed。Asitwas，Davyappearstohaverealizedthatsensibilitywasdulled，forheaddsthisilluminativesuggestion:"Asnitrousoxideinitsextensiveoperationappearscapableofdestroyingphysicalpain，itmayprobablybeusedwithadvantageduringsurgicaloperationsinwhichnogreateffusionofbloodtakesplace。"[4]
　　Unfortunatelynoonetookadvantageofthissuggestionatthetime，andDavyhimselfbecameinterestedinotherfieldsofscienceandneverreturnedtohisphysiologicalstudies，thusbarelymissingoneofthegreatestdiscoveriesintheentirefieldofscience。InthegenerationthatfollowednooneseemstohavethoughtofputtingDavy’ssuggestiontothetest，andthesurgeonsofEuropehadacknowledgedwithoneaccordthatallhopeoffindingameanstorenderoperationspainlessmustbeutterlyabandoned——thatthesurgeon’sknifemusteverremainasynonymforslowandindescribabletorture。ByanoddcoincidenceitchancedthatSirBenjaminBrodie，theacknowledgedleaderofEnglishsurgeons，hadpubliclyexpressedthisashisdeliberatethoughregrettedopinionatatimewhenthequestwhichheconsideredfutilehadalreadyledtothemostbrilliantsuccessinAmerica，andwhiletheannouncementofthediscovery，whichthenhadnotransatlanticcabletoconveyit，wasactuallyonitswaytotheOldWorld。
　　TheAmericandentistjustreferredto，whowas，withoneexceptiontobenotedpresently，thefirstmanintheworldtoconceivethattheadministrationofadefinitedrugmightrenderasurgicaloperationpainlessandtogivethebeliefapplicationwasDr。HoraceWells，ofHartford，Connecticut。Thedrugwithwhichheexperimentedwasnitrousoxide——thesamethatDavyhadused；theoperationthatherenderedpainlesswasnomoreimportantthantheextractionofatooth——yetitsufficedtomarkaprinciple；theyearoftheexperimentwas1844。
　　TheexperimentsofDr。Wells，however，thoughimportant，werenotsufficientlydemonstrativetobringthematterprominentlytotheattentionofthemedicalworld。Thedrugwithwhichheexperimentedprovednotalwaysreliable，andhehimselfseemsultimatelytohavegiventhematterup，oratleasttohaverelaxedhisefforts。Butmeantimeafriend，towhomhehadcommunicatedhisbeliefandexpectations，tookthematterup，andwithunremittingzealcarriedforwardexperimentsthatweredestinedtoleadtomoretangibleresults。Thisfriendwasanotherdentist，Dr。W。T。G。Morton，ofBoston，thenayoungmanfullofyouthfulenergyandenthusiasm。HeseemstohavefeltthatthedrugwithwhichWellshadexperimentedwasnotthemostpracticableoneforthepurpose，andsoforseveralmonthsheexperimentedwithotherallieddrugs，untilfinallyhehituponsulphuricether，andwiththiswasabletomakeexperimentsuponanimals，andthenuponpatientsinthedentalchair，thatseemedtohimabsolutelydemonstrative。
　　Fullofeagerenthusiasm，andabsolutelyconfidentofhisresults，heatoncewenttoDr。J。C。Warren，oneoftheforemostsurgeonsofBoston，andaskedpermissiontotesthisdiscoverydecisivelyononeofthepatientsattheBostonHospitalduringasevereoperation。Therequestwasgranted；thetestwasmadeonOctober16，1846，inthepresenceofseveraloftheforemostsurgeonsofthecityandofabodyofmedicalstudents。Thepatientsleptquietlywhilethesurgeon’sknifewasplied，andawoketoastonishedcomprehensionthattheordealwasover。Theimpossible，themiraculous，hadbeenaccomplished。[5]
　　Swiftlyassteamcouldcarryit——slowlyenoughweshouldthinkitto-day——thenewswasheraldedtoalltheworld。ItwasreceivedinEuropewithincredulity，whichvanishedbeforerepeatedexperiments。Surgeonswereloathtobelievethatether，adrugthathadlongheldaplaceinthesubordinatearmamentariumofthephysician，couldaccomplishsuchamiracle。Butscepticismvanishedbeforethetestswhichanysurgeonmightmake，andwhichsurgeonsallovertheworlddidmakewithinthenextfewweeks。
　　Thentherecamealingeringoutcryfromafewsurgeons，notablysomeoftheParisians，thattheshockofpainwasbeneficialtothepatient，hencethatanaesthesia——asDr。OliverWendellHolmeshadchristenedthenewmethod——wasaprocedurenottobeadvised。
　　Then，too，therecameahue-and-cryfrommanyapulpitthatpainwasGod-given，andhence，onmoralgrounds，tobeclungtoratherthanrenounced。Buttheoutcryoftheantediluviansofbothhospitalandpulpitquicklyreceiveditsquietus；forsoonitwasclearthatthepatientwhodidnotsuffertheshockofpainduringanoperationralliedbetterthantheonewhodidsosuffer，whileallhumanityoutsidethepulpitcriedshametothespiritthatwoulddoommankindtosufferneedlessagony。AndsowithinafewmonthsafterthatinitialoperationattheBostonHospitalin1846，etherhadmadegooditsconquestofpainthroughoutthecivilizedworld。Onlybythemostactiveuseoftheimaginationcanweofthispresentdayrealizethefullmeaningofthatvictory。
　　Itremainstobeaddedthatinthesubsequentbickeringsoverthediscovery——suchbickeringsasfolloweverygreatadvance——twoothernamescameintoprominentnoticeassharersinthegloryofthenewmethod。BoththesewereAmericans——theone，Dr。CharlesT。Jackson，ofBoston；theother，Dr。CrawfordW。Long，ofAlabama。AstoDr。Jackson，itissufficienttosaythatheseemstohavehadsomevagueinklingofthepeculiarpropertiesofetherbeforeMorton’sdiscovery。HeevensuggestedtheuseofthisdrugtoMorton，notknowingthatMortonhadalreadytriedit；butthisisthefullmeasureofhisassociationwiththediscovery。HenceitisclearthatJackson’sclaimtoequalsharewithMortoninthediscoverywasunwarranted，nottosayabsurd。
　　Dr。Long’sassociationwiththematterwasfardifferentandaltogetherhonorable。Byoneofthosecoincidencessocommoninthehistoryofdiscovery，hewasexperimentingwithetherasapain-destroyersimultaneouslywithMorton，thoughneithersomuchasknewoftheexistenceoftheother。Whileamedicalstudenthehadonceinhaledetherfortheintoxicanteffects，asothermedicalstudentswerewonttodo，andwhenpartiallyunderinfluenceofthedrughehadnoticedthatachanceblowtohisshinswaspainless。Thisgavehimtheideathatethermightbeusedinsurgicaloperations；andinsubsequentyears，inthecourseofhispracticeinasmallGeorgiatown，heputtheideaintosuccessfulexecution。ThereappearstobenodoubtwhateverthatheperformedsuccessfulminoroperationsunderethersometwoorthreeyearsbeforeMorton’sfinaldemonstration；hencethatthemeritoffirstusingthedrug，orindeedanydrug，inthiswaybelongstohim。But，unfortunately，Dr。Longdidnotquitetrusttheevidenceofhisownexperiments。Justatthattimethemedicaljournalswerefullofaccountsofexperimentsinwhichpainlessoperationsweresaidtobeperformedthroughpracticeofhypnotism，andDr。Longfearedthathisownsuccessmightbeduetoanincidentalhypnoticinfluenceratherthantothedrug。Hencehedelayedannouncinghisapparentdiscoveryuntilheshouldhaveopportunityforfurthertests——andopportunitiesdidnotcomeeverydaytothecountrypractitioner。
　　Andwhilehewaited，Mortonanticipatedhim，andthediscoverywasmadeknowntotheworldwithouthisaid。ItwasatruescientificcautionthatactuatedDr。Longtothisdelay，butthecautioncosthimthecredit，whichmightotherwisehavebeenhis，ofgivingtotheworldoneofthegreatestblessings——darewenot，perhaps，saytheverygreatest？——thatsciencehaseverconferreduponhumanity。
　　Afewmonthsaftertheuseofetherbecamegeneral，theScotchsurgeonSirJ。Y。Simpson[6]discoveredthatanotherdrug，chloroform，couldbeadministeredwithsimilareffects；thatitwould，indeed，inmanycasesproduceanaesthesiamoreadvantageouslyeventhanether。Fromthatdaytillthissurgeonshavebeenmoreorlessdividedinopinionastotherelativemeritsofthetwodrugs；butthisfact，ofcourse，hasnobearingwhateveruponthemeritofthefirstdiscoveryofthemethodofanaesthesia。Evenhadsomeotherdrugsubsequentlyquitebanishedether，thehonorofthediscoveryofthebeneficentmethodofanaesthesiawouldhavebeeninnowiseinvalidated。Anddespiteallcavillings，itisunequivocallyestablishedthatthemanwhogavethatmethodtotheworldwasWilliamT。G。Morton。
　　PASTEURANDTHEGERMTHEORYOFDISEASE
　　Thediscoveryoftheanaestheticpowerofdrugswasdestinedpresently，inadditiontoitsdirectbeneficences，toaidgreatlyintheprogressofscientificmedicine，byfacilitatingthoseexperimentalstudiesofanimalsfromwhich，beforethedayofanaesthesia，manyhumanephysicianswerewithheld，andwhichinrecentyearshaveledtodiscoveriesofsuchinestimablevaluetohumanity。Butforthemomentthispossibilitywasquiteovershadowedbythedirectbenefitsofanaesthesia，andthelongstridesthatweretakeninscientificmedicineduringthefirstfifteenyearsafterMorton’sdiscoveryweremainlyindependentofsuchaid。Thesestepsweretaken，indeed，inafieldthatatfirstglancemightseemtohaveaveryslightconnectionwithmedicine。Moreover，thechiefworkerinthefieldwasnothimselfaphysician。Hewasachemist，andtheworkinwhichhewasnowengagedwasthestudyofalcoholicfermentationinvinousliquors。Yetthesestudiespavedthewayforthemostimportantadvancesthatmedicinehasmadeinanycenturytowardstheplaneoftruescience；andtothismanmorethantoanyothersingleindividual——itmightalmostbesaidmorethantoallotherindividuals——wasduethiswonderfuladvance。ItisalmostsuperfluoustoaddthatthenameofthismarvellouschemistwasLouisPasteur。
　　ThestudiesoffermentationwhichPasteurentereduponin1854
　　wereaimedatthesolutionofacontroversythathadbeenwaginginthescientificworldwithvaryingdegreesofactivityforaquarterofacentury。Backinthethirties，inthedayoftheearlyenthusiasmovertheperfectedmicroscope，therehadarisenanewinterestintheminuteformsoflifewhichLeeuwenhoekandsomeoftheotherearlyworkerswiththelenshadfirstdescribed，andwhichnowwereshowntobeofalmostuniversalprevalence。Theseminuteorganismshadbeenstudiedmoreorlessbyahostofobservers，butinparticularbytheFrenchmanCagniardLatourandtheGermanofcell-theoryfame，TheodorSchwann。Thesemen，workingindependently，hadreachedtheconclusion，about1837，thatthemicro-organismsplayavastlymoreimportantroleintheeconomyofnaturethananyonepreviouslyhadsupposed。Theyheld，forexample，thattheminutespeckswhichlargelymakeupthesubstanceofyeastarelivingvegetableorganisms，andthatthegrowthoftheseorganismsisthecauseoftheimportantandfamiliarprocessoffermentation。
　　Theyevencametohold，atleasttentatively，theopinionthatthesomewhatsimilarmicro-organismstobefoundinallputrefyingmatter，animalorvegetable，hadacausalrelationtotheprocessofputrefaction。
　　Thisview，particularlyastothenatureofputrefaction，wasexpressedevenmoreoutspokenlyalittlelaterbytheFrenchbotanistTurpin。Viewssosupportednaturallygainedafollowing；itwasequallynaturalthatsoradicalaninnovationshouldbeantagonized。Inthiscaseitchancedthatoneofthemostdominatingscientificmindsofthetime，thatofLiebig，tookafirmandaggressivestandagainstthenewdoctrine。In1839hepromulgatedhisfamousdoctrineoffermentation，inwhichhestoodoutfirmlyagainstany"vitalistic"explanationofthephenomena，allegingthatthepresenceofmicro-organismsinfermentingandputrefyingsubstanceswasmerelyincidental，andinnosensecausal。ThisopinionofthegreatGermanchemistwasinameasuresubstantiatedbyexperimentsofhiscompatriotHelmholtz，whoseearlierexperimentsconfirmed，butlateronescontradicted，theobservationsofSchwann，andthiscombinedauthoritygavethevitalisticconceptionablowfromwhichithadnotralliedatthetimewhenPasteurenteredthefield。Indeed，itwascurrentlyregardedassettledthattheearlystudentsofthesubjecthadvastlyover-estimatedtheimportanceofmicro-organisms。
　　Andsoitcameasanewrevelationtothegeneralityofscientistsofthetime，when，in1857andthesucceedinghalf-decade，Pasteurpublishedtheresultsofhisresearches，inwhichthequestionhadbeenputtoaseriesofaltogethernewtests，andbroughttounequivocaldemonstration。
　　Heprovedthatthemicro-organismsdoallthathismostimaginativepredecessorshadsuspected，andmore。Withoutthem，heproved，therewouldbenofermentation，noputrefaction——nodecayofanytissues，exceptbytheslowprocessofoxidation。Itisthemicroscopicyeast-plantwhich，byseizingoncertainatomsofthemolecule，liberatestheremainingatomsintheformofcarbonic-acidandalcohol，thuseffectingfermentation；itisanothermicroscopicplant——abacterium，asDevainehadchristenedit——whichinasimilarwayeffectsthedestructionoforganicmolecules，producingtheconditionwhichwecallputrefaction。
　　Pasteurshowed，totheamazementofbiologists，thattherearecertainformsofthesebacteriawhichsecuretheoxygenwhichallorganicliferequires，notfromtheair，butbybreakingupunstablemoleculesinwhichoxygeniscombined；thatputrefaction，inshort，hasitsfoundationintheactivitiesoftheseso-calledanaerobicbacteria。
　　Inaword，Pasteurshowedthatallthemanyfamiliarprocessesofthedecayoforganictissuesare，ineffect，formsoffermentation，andwouldnottakeplaceatallexceptforthepresenceofthelivingmicro-organisms。Apieceofmeat，forexample，suspendedinanatmospherefreefromgerms，willdryupgradually，withouttheslightestsignofputrefaction，regardlessofthetemperatureorotherconditionstowhichitmayhavebeensubjected。LetuswitnessoneortwoseriesoftheseexperimentsaspresentedbyPasteurhimselfinoneofhisnumerouspapersbeforetheAcademyofSciences。
　　EXPERIMENTSWITHGRAPESUGAR
　　"InthecourseofthediscussionwhichtookplacebeforetheAcademyuponthesubjectofthegenerationoffermentsproperlyso-called，therewasagooddealsaidaboutthatofwine，theoldestfermentationknown。OnthisaccountIdecidedtodisprovethetheoryofM。Fremybyadecisiveexperimentbearingsolelyuponthejuiceofgrapes。
　　"Ipreparedfortyflasksofacapacityoffromtwohundredandfiftytothreehundredcubiccentimetresandfilledthemhalffullwithfilteredgrape-must，perfectlyclear，andwhich，asisthecaseofallacidulatedliquidsthathavebeenboiledforafewseconds，remainsuncontaminatedalthoughthecurvedneckoftheflaskcontainingthemremainconstantlyopenduringseveralmonthsoryears。
　　"InasmallquantityofwaterIwashedapartofabunchofgrapes，thegrapesandthestalkstogether，andthestalksseparately。Thiswashingwaseasilydonebymeansofasmallbadger’s-hairbrush。Thewashing-watercollectedthedustuponthesurfaceofthegrapesandthestalks，anditwaseasilyshownunderthemicroscopethatthiswaterheldinsuspensionamultitudeofminuteorganismscloselyresemblingeitherfungoidspores，orthoseofalcoholicYeast，orthoseofMycodermavini，etc。Thisbeingdone，tenofthefortyflaskswerepreservedforreference；intenoftheremainder，throughthestraighttubeattachedtoeach，somedropsofthewashing-waterwereintroduced；inathirdseriesoftenflasksafewdropsofthesameliquidwereplacedafterithadbeenboiled；and，finally，inthetenremainingflaskswereplacedsomedropsofgrape-juicetakenfromtheinsideofaperfectfruit。Inordertocarryoutthisexperiment，thestraighttubeofeachflaskwasdrawnoutintoafineandfirmpointinthelamp，andthencurved。Thisfineandclosedpointwasfiledroundneartheendandinsertedintothegrapewhilerestinguponsomehardsubstance。Whenthepointwasfelttotouchthesupportofthegrapeitwasbyaslightpressurebrokenoffatthepointfilemark。Then，ifcarehadbeentakentocreateaslightvacuumintheflask，adropofthejuiceofthegrapegotintoit，thefiledpointwaswithdrawn，andtheapertureimmediatelyclosedinthealcohollamp。Thisdecreasedpressureoftheatmosphereintheflaskwasobtainedbythefollowingmeans:Afterwarmingthesidesoftheflaskeitherinthehandsorinthelamp-flame，thuscausingasmallquantityofairtobedrivenoutoftheendofthecurvedneck，thisendwasclosedinthelamp。Aftertheflaskwascooled，therewasatendencytosuckinthedropofgrape-juiceinthemannerjustdescribed。
　　"Thedropofgrape-juicewhichentersintotheflaskbythissuctionordinarilyremainsinthecurvedpartofthetube，sothattomixitwiththemustitwasnecessarytoinclinetheflasksoastobringthemustintocontactwiththejuiceandthenreplacetheflaskinitsnormalposition。Thefourseriesofcomparativeexperimentsproducedthefollowingresults:
　　"Thefirsttenflaskscontainingthegrape-mustboiledinpureairdidnotshowtheproductionofanyorganism。Thegrape-mustcouldpossiblyremaininthemforanindefinitenumberofyears。
　　Thoseinthesecondseries，containingthewaterinwhichthegrapeshadbeenwashedseparatelyandtogether，showedwithoutexceptionanalcoholicfermentationwhichinseveralcasesbegantoappearattheendofforty-eighthourswhentheexperimenttookplaceatordinarysummertemperature。Atthesametimethattheyeastappeared，intheformofwhitetraces，whichlittlebylittleunitedthemselvesintheformofadepositonthesidesofalltheflasks，therewereseentoformlittleflakesofMycellium，oftenasasinglefungoidgrowthorincombination，thesefungoidgrowthsbeingquiteindependentofthemustorofanyalcoholicyeast。Often，also，theMycodermaviniappearedaftersomedaysuponthesurfaceoftheliquid。TheVibriaandthelacticfermentsproperlysocalleddidnotappearonaccountofthenatureoftheliquid。
　　"Thethirdseriesofflasks，thewashing-waterinwhichhadbeenpreviouslyboiled，remainedunchanged，asinthefirstseries。
　　Thoseofthefourthseries，inwhichwasthejuiceoftheinteriorofthegrapes，remainedequallyfreefromchange，althoughIwasnotalwaysable，onaccountofthedelicacyoftheexperiment，toeliminateeverychanceoferror。Theseexperimentscannotleavetheleastdoubtinthemindastothefollowingfacts:
　　Grape-must，afterheating，neverfermentsoncontactwiththeair，whentheairhasbeendeprivedofthegermswhichitordinarilyholdsinastateofsuspension。
　　"Theboiledgrape-mustfermentswhenthereisintroducedintoitaverysmallquantityofwaterinwhichthesurfaceofthegrapesortheirstalkshavebeenwashed。
　　"Thegrape-mustdoesnotfermentwhenthiswashing-waterhasbeenboiledandafterwardscooled。
　　"Thegrape-mustdoesnotfermentwhenthereisaddedtoitasmallquantityofthejuiceoftheinsideofthegrape。
　　"Theyeast，therefore，whichcausesthefermentationofthegrapesinthevintage-tubcomesfromtheoutsideandnotfromtheinsideofthegrapes。ThusisdestroyedthehypothesisofMM。
　　TrecolandFremy，whosurmisedthatthealbuminousmattertransformeditselfintoyeastonaccountofthevitalgermswhichwerenaturaltoit。Withgreaterreason，therefore，thereisnolongeranyquestionofthetheoryofLiebigofthetransformationofalbuminoidmatterintofermentsonaccountoftheoxidation。"
　　FOREIGNORGANISMSANDTHEWORTOFBEER
　　"ThemethodwhichIhavejustfollowed，"Pasteurcontinues，"inordertoshowthatthereexistsacorrelationbetweenthediseasesofbeerandcertainmicroscopicorganismsleavesnoroomfordoubt，itseemstome，inregardtotheprinciplesIamexpounding。
　　"Everytimethatthemicroscoperevealsintheleaven，andespeciallyintheactiveyeast，theproductionoforganismsforeigntothealcoholicyeastproperlysocalled，theflavorofthebeerleavessomethingtobedesired，muchorlittle，accordingtotheabundanceandthecharacteroftheselittlegerms。Moreover，whenafinishedbeerofgoodqualitylosesafteratimeitsagreeableflavorandbecomessour，itcanbeeasilyshownthatthealcoholicyeastdepositedinthebottlesorthecasks，althoughoriginallypure，atleastinappearance，isfoundtobecontaminatedgraduallywiththesefiliformorotherferments。Allthiscanbededucedfromthefactsalreadygiven，butsomecriticsmayperhapsdeclarethattheseforeignfermentsaretheconsequencesofthediseasedcondition，itselfproducedbyunknowncauses。
　　"Althoughthisgratuitoushypothesismaybedifficulttouphold，Iwillendeavortocorroboratetheprecedingobservationsbyaclearermethodofinvestigation。Thisconsistsinshowingthatthebeerneverhasanyunpleasanttasteinallcaseswhenthealcoholicfermentproperlysocalledisnotmixedwithforeignferments；thatitisthesameinthecaseofwort，andthatwort，liabletochangesasitis，canbepreservedunalteredifitiskeptfromthosemicroscopicparasiteswhichfindinitasuitablenourishmentandafieldforgrowth。
　　"Theemploymentofthissecondmethodhas，moreover，theadvantageofprovingwithcertaintythepropositionthatI
　　advancedatfirst——namely，thatthegermsoftheseorganismsarederivedfromthedustoftheatmosphere，carriedaboutanddepositeduponallobjects，orscatteredovertheutensilsandthematerialsusedinabrewery-materialsnaturallychargedwithmicroscopicgerms，andwhichthevariousoperationsinthestore-roomsandthemalt-housemaymultiplyindefinitely。
　　"Letustakeaglassflaskwithalongneckoffromtwohundredandfiftytothreehundredcubiccentimetrescapacity，andplaceinitsomewort，withorwithouthops，andthenintheflameofalampdrawouttheneckoftheflasktoafinepoint，afterwardsheatingtheliquiduntilthesteamcomesoutoftheendoftheneck。Itcanthenbeallowedtocoolwithoutanyotherprecautions；butforadditionalsafetytherecanbeintroducedintothelittlepointasmallwadofasbestosatthemomentthattheflameiswithdrawnfrombeneaththeflask。Beforethusplacingtheasbestositalsocanbepassedthroughtheflame，aswellasafterithasbeenputintotheendofthetube。Theairwhichthenfirstre-enterstheflaskwillthuscomeintocontactwiththeheatedglassandtheheatedliquid，soastodestroythevitalityofanydustgermsthatmayexistintheair。Theairitselfwillre-enterverygradually，andslowlyenoughtoenableanydusttobetakenupbythedropofwaterwhichtheairforcesupthecurvatureofthetube。Ultimatelythetubewillbedry，butthere-enteringoftheairwillbesoslowthattheparticlesofdustwillfalluponthesidesofthetube。Theexperimentsshowthatwiththiskindofvessel，allowingfreecommunicationwiththeair，andthedustnotbeingallowedtoenter，thedustwillnotenteratalleventsforaperiodoftenortwelveyears，whichhasbeenthelongestperioddevotedtothesetrials；andtheliquid，ifitwerenaturallylimpid，willnotbeintheleastpollutedneitheronitssurfacenorinitsmass，althoughtheoutsideoftheflaskmaybecomethicklycoatedwithdust。Thisisamostirrefutableproofoftheimpossibilityofdustgettinginsidetheflask。
　　"Thewortthuspreparedremainsuncontaminatedindefinitely，inspiteofitssusceptibilitytochangewhenexposedtotheairunderconditionswhichallowittogatherthedustyparticleswhichfloatintheatmosphere。Itisthesameinthecaseofurine，beef-tea，andgrape-must，andgenerallywithallthoseputrefactableandfermentableliquidswhichhavethepropertywhenheatedtoboiling-pointofdestroyingthevitalityofdustgerms。"[7]
　　Therewasnothinginthesestudiesbearingdirectlyuponthequestionofanimaldiseases，yetbeforetheywerefinishedtheyhadstimulatedprogressinmorethanonefieldofpathology。Attheveryoutsettheysufficedtostartafreshtheinquiryastotheroleplayedbymicro-organismsindisease。InparticulartheyledtheFrenchphysicianDevainetoreturntosomeinterruptedstudieswhichhehadmadetenyearsbeforeinreferencetotheanimaldiseasecalledanthrax，orsplenicfever，adiseasethatcostthefarmersofEuropemillionsoffrancsannuallythroughlossofsheepandcattle。In1850Devainehadseenmultitudesofbacteriainthebloodofanimalswhohaddiedofanthrax，buthedidnotatthattimethinkofthemashavingacausalrelationtothedisease。Now，however，in1863，stimulatedbyPasteur’snewrevelationsregardingthepowerofbacteria，hereturnedtothesubject，andsoonbecameconvinced，throughexperimentsbymeansofinoculation，thatthemicroscopicorganismshehaddiscoveredweretheveritableandthesolecauseoftheinfectiousdiseaseanthrax。
　　Thepublicationofthisbeliefin1863arousedafurorofcontroversy。Thatamicroscopicvegetablecouldcauseavirulentsystemicdiseasewasanideaaltogethertoostartlingtobeacceptedinaday，andthegeneralityofbiologistsandphysiciansdemandedmoreconvincingproofsthanDevaineasyetwasabletooffer。
　　Naturallyahostofotherinvestigatorsallovertheworldenteredthefield。ForemostamongthesewastheGermanDr。RobertKoch，whosooncorroboratedallthatDevainehadobserved，andcarriedtheexperimentsfurtherinthedirectionofthecultivationofsuccessivegenerationsofthebacteriainartificialmedia，inoculationsbeingmadefromsuchpureculturesoftheeighthgeneration，withtheastonishingresultthatanimalsthusinoculatedsuccumbedtothedisease。
　　Suchexperimentsseemdemonstrative，yettheworldwasunconvinced，andin1876，whilethecontroversywasstillatitsheight，Pasteurwasprevailedupontotakethematterinhand。
　　Thegreatchemistwasbecomingmoreandmoreexclusivelyabiologistastheyearspassed，andinrecentyearshisfamousstudiesofthesilk-wormdiseases，whichheprovedduetobacterialinfection，andofthequestionofspontaneousgeneration，hadgivenhimunequalledresourcesinmicroscopicaltechnique。Andsowhen，withtheaidofhislaboratoryassociatesDuclauxandChamberlandandRoux，hetookupthemootedanthraxquestionthescientificworldawaitedtheissuewithbatedbreath。Andwhen，in1877，Pasteurwasreadytoreportonhisstudiesofanthrax，hecameforwardwithsuchawealthofdemonstrativeexperiments——experimentstherigidaccuracyofwhichnoonewouldforamomentthinkofquestioning——goingtoprovethebacterialoriginofanthrax，thatscepticismwasatlastquietedforalltimetocome。
　　Henceforthnoonecoulddoubtthatthecontagiousdiseaseanthraxisdueexclusivelytotheintroductionintoananimal’ssystemofaspecificgerm——amicroscopicplant——whichdevelopsthere。Andnologicalmindcouldhaveareasonabledoubtthatwhatisprovedtrueofoneinfectiousdiseasewouldsomedaybeprovedtruealsoofother，perhapsofall，formsofinfectiousmaladies。
　　Hithertothecauseofcontagion，bywhichcertainmaladiesspreadfromindividualtoindividual，hadbeenatotalmystery，quiteunilluminedbythevagueterms"miasm，""humor，""virus，"andthelikecloaksofignorance。Hereandthereaprophetofscience，asSchwannandHenle，hadguessedthesecret；butguessing，inscience，isfarenoughfromknowing。Now，forthefirsttime，theworldKNEW，andmedicinehadtakenanothergiganticstridetowardstheheightsofexactscience。
　　LISTERANDANTISEPTICSURGERY
　　Meantime，inadifferentthoughalliedfieldofmedicinetherehadbeenacomplementarygrowththatledtoimmediateresultsofevenmorepracticalimportance。Imeanthetheoryandpracticeofantisepsisinsurgery。Thisadvance，liketheother，cameasadirectoutgrowthofPasteur’sfermentationstudiesofalcoholicbeverages，thoughnotatthehandsofPasteurhimself。StruckbytheboundlessimplicationsofPasteur’srevelationsregardingthebacteria，Dr。JosephListerthepresentLordLister，thenofGlasgow，setaboutasearlyas1860tomakeawonderfulapplicationoftheseideas。Ifputrefactionisalwaysduetobacterialdevelopment，heargued，thismustapplyaswelltolivingastodeadtissues；hencetheputrefactivechangeswhichoccurinwoundsandafteroperationsonthehumansubject，fromwhichblood-poisoningsooftenfollows，mightbeabsolutelypreventediftheinjuredsurfacescouldbekeptfreefromaccessofthegermsofdecay。
　　Inthehopeofaccomplishingthisresult，Listerbeganexperimentingwithdrugsthatmightkillthebacteriawithoutinjurytothepatient，andwithmeanstopreventfurtheraccessofgermsonceawoundwasfreedfromthem。Howwellhesucceededalltheworldknows；howbitterlyhewasantagonizedforaboutascoreofyears，mostoftheworldhasalreadyforgotten。Asearlyas1867Listerwasabletopublishresultspointingtowardssuccessinhisgreatproject；yetsoincredulousweresurgeonsingeneralthatevensomeyearslatertheleadingsurgeonsontheContinenthadnotsomuchasheardofhisefforts。In1870thesoldiersofParisdied，asofold，ofhospitalgangrene；andwhen，in1871，theFrenchsurgeonAlphonseGuerin，stimulatedbyPasteur’sstudies，conceivedtheideaofdressingwoundswithcottoninthehopeofkeepinggermsfromenteringthem，hewasquiteunawarethataBritishcontemporaryhadprecededhimbyafulldecadeinthiseffortatpreventionandhadmadelongstridestowardscompletesuccess。Lister’spriority，however，andthesuperiorityofhismethod，werefreelyadmittedbytheFrenchAcademyofSciences，whichin1881officiallycrownedhisachievement，astheRoyalSocietyofLondonhaddonetheyearbefore。
　　Bythistime，tobesure，aseverybodyknows，Lister’snewmethodshadmadetheirwayeverywhere，revolutionizingthepracticeofsurgeryandpracticallybanishingfromtheearthmaladiesthathithertohadbeentheterrorofthesurgeonandtheopprobriumofhisart。Andthesebedsidestudies，conductedintheendbythousandsofmenwhohadnoknowledgeofmicroscopy，hadalargeshareinestablishingthegeneralbeliefinthecausalrelationthatmicro-organismsbeartodisease，whichbyabouttheyear1880hadtakenpossessionofthemedicalworld。
　　Buttheydidmore；theybroughtintoequalprominencetheideathat，thecauseofadiseasedconditionbeingknown，itmaybepossibleasneverbeforetograpplewithanderadicatethatcondition。