ded　upon　a　sufficient　purification　of　the　air；　by　means　of　large　blazing　fires　of　odoriferous　wood；　in　the　vicinity　of　the　healthy　as　well　as　of　the　sick；　and　also　upon　an　appropriate　manner　of　living；　so　that　the　putridity　might　not　overpower　the　diseased。　　In　conformity　with　notions　derived　from　the　ancients；　he　depended　upon　bleeding　and　purging；　at　the　commencement　of　the　attack；　for　the　purpose　of　purification；　ordered　the　healthy　to　wash　themselves　frequently　with　vinegar　or　wine；　to　sprinkle　their　dwellings　with　vinegar；　and　to　smell　often　to　camphor；　or　other　volatile　substances。　　Hereupon　he　gave；　after　the　Arabian　fashion；　detailed　rules；　with　an　abundance　of　different　medicines；　of　whose　healing　powers　wonderful　things　were　believed。　　He　had　little　stress　upon　super…lunar　influences；　so　far　as　respected　the　malady　itself；　on　which　account；　he　did　not　enter　into　the　great　controversies　of　the　astrologers；　but　always　kept　in　view；　as　an　object　of　medical　attention；　the　corruption　of　the　blood　in　the　lungs　and　heart。　　He　believed　in　a　progressive　infection　from　country　to　country；　according　to　the　notions　of　the　present　day；　and　the　contagious　power　of　the　disease；　even　in　the　vicinity　of　those　affected　by　plague；　was；　in　his　opinion；　beyond　all　doubt。　　On　this　point　intelligent　contemporaries　were　all　agreed；　and；　in　truth；　it　required　no　great　genius　to　be　convinced　of　so　palpable　a　fact。　　Besides；　correct　notions　of　contagion　have　descended　from　remote　antiquity；　and　were　maintained　unchanged　in　the　fourteenth　century。　　So　far　back　as　the　age　of　Plato　a　knowledge　of　the　contagious　power　of　malignant　inflammations　of　the　eye；　of　which　also　no　physician　of　the　Middle　Ages　entertained　a　doubt；　was　general　among　the　people；　yet　in　modern　times　surgeons　have　filled　volumes　with　partial　controversies　on　this　subject。　　The　whole　language　of　antiquity　has　adapted　itself　to　the　notions　of　the　people　respecting　the　contagion　of　pestilential　diseases；　and　their　terms　were；　beyond　comparison；　more　expressive　than　those　in　use　among　the　moderns。
  Arrangements　for　the　protection　of　the　healthy　against　contagious　diseases；　the　necessity　of　which　is　shown　from　these　notions；　were　regarded　by　the　ancients　as　useful；　and　by　man；　whose　circumstances　permitted　it；　were　carried　into　effect　in　their　houses。　　Even　a　total　separation　of　the　sick　from　the　healthy；　that　indispensable　means　of　protection　against　infection　by　contact；　was　proposed　by　physicians　of　the　second　century　after　Christ；　in　order　to　check　the　spreading　of　leprosy。　　But　it　was　decidedly　opposed；　because；　as　it　was　alleged；　the　healing　art　ought　not　to　be　guilty　of　such　harshness。　　This　mildness　of　the　ancients；　in　whose　manner　of　thinking　inhumanity　was　so　often　and　so　undisguisedly　conspicuous；　might　excite　surprise　if　it　were　anything　more　than　apparent。　　The　true　ground　of　the　neglect　of　public　protection　against　pestilential　diseases　lay　in　the　general　notion　and　constitution　of　human　societyit　lay　in　the　disregard　of　human　life；　of　which　the　great　nations　of　antiquity　have　given　proofs　in　every　page　of　their　history。　　Let　it　not　be　supposed　that　they　wanted　knowledge　respecting　the　propagation　of　contagious　diseases。　　On　the　contrary；　they　were　as　well　informed　on　this　subject　as　the　modern；　but　this　was　shown　where　individual　property；　not　where　human　life；　on　the　grand　scale　was　to　be　protected。　　Hence　the　ancients　made　a　general　practice　of　arresting　the　progress　of　murrains　among　cattle　by　a　separation　of　the　diseased　from　the　healthy。　　Their　herds　alone　enjoyed　that　protection　which　they　held　it　impracticable　to　extend　to　human　society；　because　they　had　no　wish　to　do　so。　　That　the　governments　in　the　fourteenth　century　were　not　yet　so　far　advanced　as　to　put　into　practice　general　regulations　for　checking　the　plague　needs　no　especial　proof。　　Physicians　could；　therefore；　only　advise　public　purifications　of　the　air　by　means　of　large　fires；　as　had　often　been　practised　in　ancient　times；　and　they　were　obliged　to　leave　it　to　individual　families　either　to　seek　safety　in　flight；　or　to　shut　themselves　up　in　their　dwellings；　a　method　which　answers　in　common　plagues；　but　which　here　afforded　no　complete　security；　because　such　was　the　fury　of　the　disease　when　it　was　at　its　height；　that　the　atmosphere　of　whole　cities　was　penetrated　by　the　infection。
  Of　the　astral　influence　which　was　considered　to　have　originated　the　〃Great　Mortality；〃　physicians　and　learned　men　were　as　completely　convinced　as　of　the　fact　of　its　reality。　　A　grand　conjunction　of　the　three　superior　planets；　Saturn；　Jupiter；　and　Mars；　in　the　sign　of　Aquarius；　which　took　place；　according　to　Guy　de　Chauliac；　on　the　24th　of　March；　1345；　was　generally　received　as　its　principal　cause。　　In　fixing　the　day；　this　physician；　who　was　deeply　versed　in　astrology；　did　not　agree　with　others；　whereupon　there　arose　various　disputations；　of　weight　in　that　age；　but　of　none　in　ours。　　People；　however；　agree　in　thisthat　conjunctions　of　the　planets　infallibly　prognosticated　great　events；　great　revolutions　of　kingdoms；　new　prophets；　destructive　plagues；　and　other　occurrences　which　bring　distress　and　horror　on　mankind。　　No　medical　author　of　the　fourteenth　and　fifteenth　centuries　omits　an　opportunity　of　representing　them　as　among　the　general　prognostics　of　great　plagues；　nor　can　we；　for　our　part；　regard　the　astrology　of　the　Middle　Ages　as　a　mere　offspring　of　superstition。　　It　has　not　only；　in　common　with　all　ideas　which　inspire　and　guide　mankind；　a　high　historical　importance；　entirely　independent　of　its　error　or　truthfor　the　influence　of　both　is　equally　powerfulbut　there　are　also　contained　in　it；　as　in　alchemy；　grand　thoughts　of　antiquity；　of　which　modern　natural　philosophy　is　so　little　ashamed　that　she　claims　them　as　her　property。　　Foremost　among　these　is　the　idea　of　general　life　which　diffuses　itself　throughout　the　whole　universe；　expressed　by　the　greatest　Greek　sages；　and　transmitted　to　the　Middle　Ages；　through　the　new　Platonic　natural　philosophy。　To　this　impression　of　an　universal　organism；　the　assumption　of　a　reciprocal　influence　of　terrestrial　bodies　could　not　be　foreign；　nor　did　this　cease　to　correspond　with　a　higher　view　of　nature；　until　astrologers　overstepped　the　limits　of　human　knowledge　with　frivolous　and　mystical　calculations。
  Guy　de　Chauliac　considers　the　influence　of　the　conjunction；　which　was　held　to　be　all…potent；　as　the　chief　general　cause　of　the　Black　Plague；　and　the　diseased　state　of　bodies；　the　corruption　of　the　fluids；　debility；　obstruction；　and　so　forth；　as　the　especial　subordinate　causes。　　By　these；　according　to　his　opinion；　the　quality　of　the　air；　and　of　the　other　elements；　was　so　altered　that　they　set　poisonous　fluids　in　motion　towards　the　inward　parts　of　the　body；　in　the　same　manner　as　the　magnet　attracts　iron；　whence　there　arose　in　the　commencement　fever　and　the　spitting　of　blood；　afterwards；　however；　a　deposition　in　the　form　on　glandular　swellings　and　inflammatory　boils。　　Herein　the　notion　of　an　epidemic　constitution　was　set　forth　clearly；　and　conformably　to　the　spirit　of　the　age。　　Of　contagion；　Guy　de　Chauliac　was　completely　convinced。　　He　sought　to　protect　himself　against　it　by　the　usual　means；　and　it　was　probably　he　who　advised　Pope　Clement　VI。　to　shut　himself　up　while　the　plague　lasted。　　The　preservation　of　this　Pope's　life；　however；　was　most　beneficial　to　the　city　of　Avignon；　for　he　loaded　the　poor　with　judicious　acts　of　kindness；　took　care　to　have　proper　attendants　provided；　and　paid　physicians　himself　to　afford　assistance　wherever　human　aid　could　availan　advantage　which；　perhaps；　no　other　city　enjoyed。　　Nor　was　the　treatment　of　plague…patients　in　Avignon　by　any　means　objectionable；　for；　after　the　usual　depletions　by　bleeding　and　aperients；　where　circumstances　required　them；　they　endeavoured　to　bring　the　buboes　to　suppuration；　they　made　incisions　into　the　inflammatory　boils；　or　burned　them　with　a　red…hot　iron；　a　practice　which　at　all　times　proves　salutary；　and　in　the　Black　Plague　saved　many　lives。　　In　this　city；　the　Jews；　who　lived　in　a　state　of　the　greatest　filth；　were　most　severely　visited；　as　also　the　Spaniards；　whom　Chalin　accuses　of　great　intemperance。
  Still　more　distinct　notions　on　the　causes　of　the　plague　were　stated　to　his　contemporaries　in　the　fourteenth　century　by　Galeazzo　di　Santa　Sofia；　a　learned　man；　a　native　of　Padua；　who　likewise　treated　plague…patients　at　Vienna；　though　in　what　year　is　undetermined。　　He　distinguishes　carefully　PESTILENCE　from　EPIDEMY　and　ENDEMY。　　The　common　notion　of　the　two　first　accords　exactly　with　that　of　an　epidemic　constitution；　for　both　consist；　according　to　him；　in　an　unknown　change　or　corruption　of　the　air；　with　this　difference；　that　pestilence　calls　forth　diseases　of　different　kinds；　epidemy；　on　the　contrary；　always　the　same　disease。　　As　an　example　of　an　epidemy；　he　adduces　a　cough　（influenza）　which　was　observed　in　all　climates　at　the　same　time　without　perceptible　cause；　but　he　recognised　the　approach　of　a　pestilence；　independently　of　unusual　natural　phenomena；　by　the　more　frequent　occurrence　of　various　kinds　of　fever；　to　which　the　modern　physicians　would　assign　a　nervous　and　putrid　character。　　The　endemy　originates；　according　to　him；　only　in　local　telluric　chang