Theactivityofpureradiumexceededallourexpectations.Forequalweightsthissubstanceemitsaradiationmorethanamilliontimesmoreintensethanuranium.Tooffsetthis,thequantityofradiumcontainedinuraniummineralsisscarcelymorethanthreedecigrammesofradiumtothetonofuranium.Thereisaverycloserelationbetweenthesetwosubstances.Infact,weknowto-daythatradiumisproducedinthemineralsattheexpenseofuranium.
TheyearsthatfollowedhisnominationtotheP.C.N.werehardforPierreCurie.Hehadtofacethemanyanxietiesincidenttotheorganizationofacomplicatedsystemofworkwhenhishappinessdependedonhisbeingabletoconcentratehiseffortsonasingledeterminedsubject.Thephysicalfatigueduetothenumerouscourseshewasobligedtogivewassogreatthathesufferedfromattacksofacutepain,whichinhisovertaxedconditionbecamemoreandmorefrequent.
Itwasthereforevitallyimportant,ifhewastosparehisenergyandkeephishealth,thattheburdenofhisprofessionaldutiesbelightened.HedecidedtoapplyfortheChairofMineralogy,whichwasvacant,attheSorbonne,forwhichhewasentirelyqualifiedbecauseofhisprofoundknowledgeandhisimportantpublicationsonthetheoriesofthephysicsofcrystals.Yethiscandidacyfailed.
Duringthispainfulperiodheneverthelessmanaged,byatrulysuperhumaneffort,successfullytocompleteandpublishseveralinvestigationsthathehadmadeeitheraloneorincollaboration:Investigationsoninducedradioactivity(incollaborationwithA.Debierne).Investigationsonthesamesubject(incollaborationwithJ.Danne).
InvestigationsontheconductibilityprovokedindielectricliquidsbytheraysofradiumandtheRoentgenrays.Investigationsonthelawofthedecreaseoftheemanationofradiumandontheradioactiveconstantsthatcharacterizethisemanationanditsactivedeposit.Discoveryoftheliberationofheatproducedbyradium(incollaborationwithA.Laborde).Investigationsonthediffusionoftheemanationofradiumintheair(incollaborationwithJ.Danne).Investigationontheradioactivityofgasesfromthermalsprings(incollaborationwithA.Laborde).Investigationonthephysiologicaleffectsofradiumrays(incommonwithHenriBecquerel).Investigationonthephysiologicalactionoftheradiumemanation(incommonwithBouchardandBalthazard).Notesontheapparatusforthedeterminationofmagneticconstants(incommonwithC.Cheneveau).
Alltheseinvestigationsinradioactivityarefundamentalandtouchveryvariedsubjects.Severalhaveastheiraimthestudyoftheemanation,thatstrangegaseousbodythatradiumproducesandwhichislargelyresponsiblefortheintenseradiationcommonlyattributedtotheradiumitself.PierreCuriedemonstratedbyasearchingexaminationtherigorousandinvariablelawaccordingtowhichtheemanationdestroysitself,nomatterwhattheconditionsareinwhichitfindsitself.To-daytheemanationofradium,harvestedintinyphials,iscommonlyemployedbyphysiciansasatherapeuticagent.Technicalconsiderationsmakeitsemploymentpreferabletothedirectuseofradium,andinthiscasenophysiciancanproceedwithoutconsultingthenumericalchartwhichtellshowmuchofthisemanationhasdisappearedeachday,despitethefactthatitiscloisteredinitslittleglassprison.Itisthissameemanationthatisfoundinsmallquantitiesinmineralwaters,andthatplaysapartintheircurativeeffects.
Morestrikingstillwasthediscoveryofthedischargeofheatfromradium.Withoutanyalterationinappearancethissubstancereleaseseachhouraquantityofheatsufficienttomeltitsownweightofice.Whenwellprotectedagainstthisexternalloss,radiumheatsitself.Itstemperaturecanrisedegreesormoreabovethatofthesurroundingatmosphere.Thisdefiedallcontemporaryscientificexperience.
Finally,Icannotpassinsilence,becauseoftheirvariousrepercussions,theexperimentsconnectedwiththephysiologicaleffectsofradium.
InordertotesttheresultsthathadjustbeenannouncedbyF.Giesel,PierreCurie,voluntarilyexposedhisarmtotheactionofradiumduringseveralhours.Thisresultedinalesionresemblingaburn,thatdevelopedprogressivelyandrequiredseveralmonthstoheal.HenriBecquerelhadbyaccidentasimilarburnasaresultofcarryinginhisvestpocketaglasstubecontainingradiumsalt.Hecametotellusofthisevileffectofradium,exclaiminginamanneratoncedelightedandannoyed:"Iloveit,butIoweitagrudge!"
Sinceherealizedtheinterestinthesephysiologicaleffectsofradium,PierreCurieundertook,incollaborationwithphysicians,theinvestigationstowhichIhavejustreferred,submittinganimalstotheactionofradiumemanation.Thesestudiesformedthepointofdepartureinradiumtherapy.ThefirstattemptsattreatmentwithradiumweremadewithproductsloanedbyPierreCurie,andhadastheirobjectthecureoflupusandotherskinlesions.Thusradiumtherapy,animportantbranchofmedicine,andfrequentlydesignatedasCurie-therapie,wasborninFrance,andwasdevelopedfirstthroughtheinvestigationsofFrenchphysicians(Danlos,Oudin,Wickham,Dominici,Cheron,Degrais,andothers).