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。