a history of science-2-第33章

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　way　to　the　heart；　just　as　the　valves　of　the　heart　itself　prevent　regurgitation；　has　been　known　since　the　time　of　Harvey；　but　the　best　interpretation　that　could　be　given　at　that　time；　even　by　such　a　man　as　Fabricius；　was　that　they　acted　in　retarding　the　flow　of　the　blood　as　it　comes　from　the　heart；　and　thus　prevent　its　too　rapid　distribution　throughout　the　body。　The　fact　that　the　blood　might　have　been　going　towards　the　heart；　instead　of　coming　from　it；　seems　never　to　have　been　considered　seriously　until　demonstrated　so　conclusively　by　Harvey。　Of　this　important　and　remarkable　controversy　over　the　valves　in　veins；　Withington　has　this　to　say：　〃This　is　truly　a　marvellous　story。　A　great　Galenic　anatomist　is　first　to　give　a　full　and　correct　description　of　the　valves　and　their　function；　but　fails　to　see　that　any　modification　of　the　old　view　as　to　the　motion　of　the　blood　is　required。　Two　able　dissectors　carefully　test　their　action　by　experiment；　and　come　to　a　result。　the　exact　reverse　of　the　truth。　Urged　by　them；　the　two　foremost　anatomists　of　the　age　make　a　special　search　for　valves　and　fail　to　find　them。　Finally；　passing　over　lesser　peculiarities；　an　aged　and　honorable　professor；　who　has　lived　through　all　this；　calmly　asserts　that　no　anatomist；　ancient　or　modern；　has　ever　mentioned　valves　in　veins　till　he　discovered　them　in　1574！〃＇2＇　Among　the　anatomists　who　probably　discovered　these　valves　was　Michael　Servetus　（1511…1553）；　but　if　this　is　somewhat　in　doubt；　it　is　certain　that　he　discovered　and　described　the　pulmonary　circulation；　and　had　a　very　clear　idea　of　the　process　of　respiration　as　carried　on　in　the　lungs。　The　description　was　contained　in　a　famous　document　sent　to　Calvin　in　1545a　document　which　the　reformer　carefully　kept　for　seven　years　in　order　that　he　might　make　use　of　some　of　the　heretical　statements　it　contained　to　accomplish　his　desire　of　bringing　its　writer　to　the　stake。　The　awful　fate　of　Servetus；　the　interesting　character　of　the　man；　and　the　fact　that　he　came　so　near　to　anticipating　the　discoveries　of　Harvey　make　him　one　of　the　most　interesting　figures　in　medical　history。　In　this　document　which　was　sent　to　Calvin；　Servetus　rejected　the　doctrine　of　natural；　vital；　and　animal　spirits；　as　contained　in　the　veins；　arteries；　and　nerves　respectively；　and　made　the　all…important　statement　that　the　fluids　contained　in　veins　and　arteries　are　the　same。　He　showed　also　that　the　blood　is　〃purged　from　fume〃　and　purified　by　respiration　in　the　lungs；　and　declared　that　there　is　a　new　vessel　in　the　lungs；　〃formed　out　of　vein　and　artery。〃　Even　at　the　present　day　there　is　little　to　add　to　or　change　in　this　description　of　Servetus's。　By　keeping　this　document；　pregnant　with　advanced　scientific　views；　from　the　world；　and　in　the　end　only　using　it　as　a　means　of　destroying　its　author；　the　great　reformer　showed　the　same　jealousy　in　retarding　scientific　progress　as　had　his　arch…enemies　of　the　Inquisition；　at　whose　dictates　Vesalius　became　a　martyr　to　science；　and　in　whose　dungeons　etienne　perished。

THE　COMING　OF　HARVEY　The　time　was　ripe　for　the　culminating　discovery　of　the　circulation　of　the　blood；　but　as　yet　no　one　had　determined　the　all…important　fact　that　there　are　two　currents　of　blood　in　the　body；　one　going　to　the　heart；　one　coming　from　it。　The　valves　in　the　veins　would　seem　to　show　conclusively　that　the　venous　current　did　not　come　from　the　heart；　and　surgeons　must　have　observed　thousands　of　times　the　every…day　phenomenon　of　congested　veins　at　the　distal　extremity　of　a　limb　around　which　a　ligature　or　constriction　of　any　kind　had　been　placed；　and　the　simultaneous　depletion　of　the　vessels　at　the　proximal　points　above　the　ligature。　But　it　should　be　remembered　that　inductive　science　was　in　its　infancy。　This　was　the　sixteenth；　not　the　nineteenth　century；　and　few　men　had　learned　to　put　implicit　confidence　in　their　observations　and　convictions　when　opposed　to　existing　doctrines。　The　time　was　at　hand；　however；　when　such　a　man　was　to　make　his　appearance；　and；　as　in　the　case　of　so　many　revolutionary　doctrines　in　science；　this　man　was　an　Englishman。　It　remained　for　William　Harvey　（1578…1657）　to　solve　the　great　mystery　which　had　puzzled　the　medical　world　since　the　beginning　of　history；　not　only　to　solve　it；　but　to　prove　his　case　so　conclusively　and　so　simply　that　for　all　time　his　little　booklet　must　he　handed　down　as　one　of　the　great　masterpieces　of　lucid　and　almost　faultless　demonstration。　Harvey；　the　son　of　a　prosperous　Kentish　yeoman；　was　born　at　Folkestone。　His　education　was　begun　at　the　grammar…school　of　Canterbury；　and　later　he　became　a　pensioner　of　Caius　College；　Cambridge。　Soon　after　taking　his　degree　of　B。A。；　at　the　age　of　nineteen；　he　decided　upon　the　profession　of　medicine；　and　went　to　Padua　as　a　pupil　of　Fabricius　and　Casserius。　Returning　to　England　at　the　age　of　twenty…four；　he　soon　after　（1609）　obtained　the　reversion　of　the　post　of　physician　to　St。　Bartholomew's　Hospital；　his　application　being　supported　by　James　I。　himself。　Even　at　this　time　he　was　a　popular　physician；　counting　among　his　patients　such　men　as　Francis　Bacon。　In　1618　he　was　appointed　physician　extraordinary　to　the　king；　and；　a　little　later；　physician　in　ordinary。　He　was　in　attendance　upon　Charles　I。　at　the　battle　of　Edgehill；　in　1642；　where；　with　the　young　Prince　of　Wales　and　the　Duke　of　York；　after　seeking　shelter　under　a　hedge；　he　drew　a　book　out　of　his　pocket　and；　forgetful　of　the　battle；　became　absorbed　in　study；　until　finally　the　cannon…balls　from　the　enemy's　artillery　made　him　seek　a　more　sheltered　position。　On　the　fall　of　Charles　I。　he　retired　from　practice；　and　lived　in　retirement　with　his　brother。　He　was　then　well　along　in　years；　but　still　pursued　his　scientific　researches　with　the　same　vigor　as　before；　directing　his　attention　chiefly　to　the　study　of　embryology。　On　June　3；　1657；　he　was　attacked　by　paralysis　and　died；　in　his　eightieth　year。　He　had　lived　to　see　his　theory　of　the　circulation　accepted；　several　years　before；　by　all　the　eminent　anatomists　of　the　civilized　world。　A　keenness　in　the　observation　of　facts；　characteristic　of　the　mind　of　the　man；　had　led　Harvey　to　doubt　the　truth　of　existing　doctrines　as　to　the　phenomena　of　the　circulation。　Galen　had　taught　that　〃the　arteries　are　filled；　like　bellows；　because　they　are　expanded；〃　but　Harvey　thought　that　the　action　of　spurting　blood　from　a　severed　vessel　disproved　this。　For　the　spurting　was　remittant；　〃now　with　greater；　now　with　less　impetus；〃　and　its　greater　force　always　corresponded　to　the　expansion　（diastole）；　not　the　contraction　（systole）　of　the　vessel。　Furthermore；　it　was　evident　that　contraction　of　the　heart　and　the　arteries　was　not　simultaneous；　as　was　commonly　taught；　because　in　that　case　there　would　be　no　marked　propulsion　of　the　blood　in　any　direction；　and　there　was　no　gainsaying　the　fact　that　the　blood　was　forcibly　propelled　in　a　definite　direction；　and　that　direction　away　from　the　heart。　Harvey's　investigations　led　him　to　doubt　also　the　accepted　theory　that　there　was　a　porosity　in　the　septum　of　tissue　that　divides　the　two　ventricles　of　the　heart。　It　seemed　unreasonable　to　suppose　that　a　thick　fluid　like　the　blood　could　find　its　way　through　pores　so　small　that　they　could　not　be　demonstrated　by　any　means　devised　by　man。　In　evidence　that　there　could　be　no　such　openings　he　pointed　out　that；　since　the　two　ventricles　contract　at　the　same　time；　this　process　would　impede　rather　than　facilitate　such　an　intra…ventricular　passage　of　blood。　But　what　seemed　the　most　conclusive　proof　of　all　was　the　fact　that　in　the　foetus　there　existed　a　demonstrable　opening　between　the　two　ventricles；　and　yet　this　is　closed　in　the　fully　developed　heart。　Why　should　Nature；　if　she　intended　that　blood　should　pass　between　the　two　cavities；　choose　to　close　this　opening　and　substitute　microscopic　openings　in　place　of　it？　It　would　surely　seem　more　reasonable　to　have　the　small　perforations　in　the　thin；　easily　permeable　membrane　of　the　foetus；　and　the　opening　in　the　adult　heart；　rather　than　the　reverse。　From　all　this　Harvey　drew　his　correct　conclusions；　declaring　earnestly；　〃By　Hercules；　there　ARE　no　such　porosities；　and　they　cannot　be　demonstrated。〃　Having　convinced　himself　that　no　intra…ventricular　opening　existed；　he　proceeded　to　study　the　acti