that　Fabricius　had　employed　to　show　the　valves；　to　demonstrate　that　the　blood　in　the　veins　flows　towards　the　heart。　　For　the　first　time　a　proper　explanation　of　the　action　of　the　valves　is　given。　Harvey　had　no　appreciation　of　how　the　arteries　and　veins　communicated　with　each　other。　　Galen；　you　may　remember；　recognized　that　there　were　anastomoses；　but　Harvey　preferred　the　idea　of　filtration。
  The　〃De　Motu　Cordis〃　constitutes　a　unique　piece　of　work　in　the　history　of　medicine。　　Nothing　of　the　same　type　had　appeared　before。　It　is　a　thoroughly　sensible；　scientific　study　of　a　definite　problem；　the　solution　of　which　was　arrived　at　through　the　combination　of　accurate　observation　and　ingenious　experiment。　Much　misunderstanding　has　arisen　in　connection　with　Harvey's　discovery　of　the　circulation　of　the　blood。　He　did　not　discover　that　the　blood　moved；that　was　known　to　Aristotle　and　to　Galen；　from　both　of　whom　I　have　given　quotations　which　indicate　clearly　that　they　knew　of　its　movement；but　at　the　time　of　Harvey　not　a　single　anatomist　had　escaped　from　the　domination　of　Galen's　views。　Both　Servetus　and　Colombo　knew　of　the　pulmonary　circulation；　which　was　described　by　the　former　in　very　accurate　terms。　　Cesalpinus；　a　great　name　in　anatomy　and　botany；　for　whom　is　claimed　the　discovery　of　the　circulation；　only　expressed　the　accepted　doctrines　in　the　following　oft…quoted　phrase：
  〃We　will　now　consider　how　the　attraction　of　aliment　and　the　process　of　nutrition　takes　place　in　plants；　for　in　animals　we　see　the　aliment　brought　through　the　veins　to　the　heart；　as　to　a　laboratory　of　innate　heat；　and；　after　receiving　there　its　final　perfection；　distributed　through　the　arteries　to　the　body　at　large；　by　the　agency　of　the　spirits　produced　from　this　same　aliment　in　the　heart。〃＇30＇　There　is　nothing　in　this　but　Galen's　view；　and　Cesalpinus　believed；　as　did　all　his　contemporaries；　that　the　blood　was　distributed　through　the　body　by　the　vena　cava　and　its　branches　for　the　nourishment　of　all　its　parts。＇*＇　To　those　who　have　any　doubts　as　to　Harvey's　position　in　this　matter　I　would　recommend　the　reading　of　the　〃De　Motu　Cordis〃　itself；　then　the　various　passages　relating　to　the　circulation　from　Aristotle　to　Vesalius。　　Many　of　these　can　be　found　in　the　admirable　works　of　Dalton；　Flourens；　Richet　and　Curtis。＇31＇　In　my　Harveian　Oration　for　1906＇32＇　I　have　dealt　specially　with　the　reception　of　the　new　views；　and　have　shown　how　long　it　was　before　the　reverence　for　Galen　allowed　of　their　acceptance。　The　University　of　Paris　opposed　the　circulation　of　the　blood　for　more　than　half　a　century　after　the　appearance　of　the　〃De　Motu　Cordis。〃
  ＇30＇　De　Plantis；　Lib　I；　cap。　2。
  ＇*＇　Cesalpinus　has　also　a　definite　statement　of　the　circlewise　process。Ed。
  ＇31＇　J。　C。　Dalton　Doctrines　of　the　Circulation；　Philadelphia；　1884；　Flourens　Histoire　de　la　decouverte　de　la　circulation　du　sang；　2d　ed。；　Paris；　1857；　Charles　Richet　Harvey；　la　circulation　du　sang；　Paris；　1879；　John　G。　Curtis　Harvey's　views　on　the　use　of　Circulation；　etc。；　New　York；　1916。
  ＇32＇　Osler　An　Alabama　Student　and　Other　Biographical　Essays；　Oxford；　1908；　p。　295。
  To　summarizeuntil　the　seventeenth　century　there　were　believed　to　be　two　closed　systems　in　the　circulation；　（1）　the　natural；　containing　venous　blood；　had　its　origin　in　the　liver　from　which；　as　from　a　fountain；　the　blood　continually　ebbed　and　flowed　for　the　nourishment　of　the　body；　（2）　the　vital；　containing　another　blood　and　the　spirits；　ebbed　and　flowed　from　the　heart；　distributing　heat　and　life　to　all　parts。　Like　a　bellows　the　lungs　fanned　and　cooled　this　vital　blood。　Here　and　there　we　find　glimmering　conceptions　of　a　communication　between　these　systems；　but　practically　all　teachers　believed　that　the　only　one　of　importance　was　through　small　pores　in　the　wall　separating　the　two　sides　of　the　heart。　　Observationmerely　looking　at　and　thinking　about　thingshad　done　all　that　was　possible；　and　further　progress　had　to　await　the　introduction　of　a　new　method；　viz。；　experiment。　　Galen；　it　is　true；　had　used　this　means　to　show　that　the　arteries　of　the　body　contained　blood　and　not　air。　The　day　had　come　when　men　were　no　longer　content　with　accurate　description　and　with　finely　spun　theories　and　dreams。　It　was　reserved　for　the　immortal　Harvey　to　put　into　practice　the　experimental　method　by　which　he　demonstrated　conclusively　that　the　blood　moved　in　a　circle。　　The　〃De　Motu　Cordis〃　marks　the　final　break　of　the　modern　spirit　with　the　old　traditions。　It　took　long　for　men　to　realize　the　value　of　this　〃inventum　mirabile〃　used　so　effectively　by　the　Alexandriansby　Galenindeed；　its　full　value　has　only　been　appreciated　within　the　past　century。　Let　me　quote　a　paragraph　from　my　Harveian　Oration。＇33＇　〃To　the　age　of　the　hearer；　in　which　men　had　heard　and　heard　only；　had　succeeded　the　age　of　the　eye　in　which　men　had　seen　and　had　been　content　only　to　see。　　But　at　last　came　the　age　of　the　hand　the　thinking；　devising；　planning　hand；　the　hand　as　an　instrument　of　the　mind；　now　re…introduced　into　the　world　in　a　modest　little　monograph　from　which　we　may　date　the　beginning　of　experimental　medicine。〃
  ＇33＇　Osler：　　An　Alabama　Student；　etc。；　pp。　329…330。
  Harvey　caught　the　experimental　spirit　in　Italy；　with　brain；　eye　and　hand　as　his　only　aids；　but　now　an　era　opened　in　which　medicine　was　to　derive　an　enormous　impetus　from　the　discovery　of　instruments　of　precision。　〃The　new　period　in　the　development　of　the　natural　sciences；　which　reached　its　height　in　the　work　of　such　men　as　Galileo；　Gilbert　and　Kepler；　is　chiefly　characterized　by　the　invention　of　very　important　instruments　for　aiding　and　intensifying　the　perceptions　of　the　senses；　by　means　of　which　was　gained　a　much　deeper　insight　into　the　phenomena　than　had　hitherto　been　possible。　　Such　instruments　as　the　earlier　ages　possessed　were　little　more　than　primitive　hand…made　tools。　Now　we　find　a　considerable　number　of　scientifically　made　instruments　deliberately　planned　for　purposes　of　special　research；　and　as　it　were；　on　the　threshold　of　the　period　stand　two　of　the　most　important；　the　compound　microscope　and　the　telescope。　　The　former　was　invented　about　1590　and　the　latter　about　1608。〃＇34＇　It　was　a　fellow　professor　of　the　great　genius　Galileo　who　attempted　to　put　into　practice　the　experimental　science　of　his　friend。　　With　Sanctorius　began　the　studies　of　temperature；　respiration　and　the　physics　of　the　circulation。　The　memory　of　this　great　investigator　has　not　been　helped　by　the　English　edition　of　his　〃De　Statica　Medicina；〃　not　his　best　work；　with　a　frontispiece　showing　the　author　in　his　dietetic　balance。　Full　justice　has　been　done　to　him　by　Dr。　Weir　Mitchell　in　an　address　as　president　of　the　Congress　of　Physicians　and　Surgeons；　1891。＇35＇　Sanctorius　worked　with　a　pulsilogue　devised　for　him　by　Galileo；　with　which　he　made　observations　on　the　pulse。　He　is　said　to　have　been　the　first　to　put　in　use　the　clinical　thermometer。　His　experiments　on　insensible　perspiration　mark　him　as　one　of　the　first　modern　physiologists。
  ＇34＇　Dannemann：　　Die　Naturwissenschaften　in　ihrer　Entwickelung。。。；　Vol。　II；　p。　7；　Leipzig；　1911。
  ＇35＇　See　Transactions　Congress　Physicians　and　Surgeons；　1891；　New　Haven；　1892；　II；　159…181。
  But　neither　Sanctorius　nor　Harvey　had　the　immediate　influence　upon　their　contemporaries　which　the　novel　and　stimulating　character　of　their　work　justified。　　Harvey's　great　contemporary；　Bacon；　although　he　lost　his　life　in　making　a　cold　storage　experiment；　did　not　really　appreciate　the　enormous　importance　of　experimental　science。　　He　looked　very　coldly　upon　Harvey's　work。　It　was　a　philosopher　of　another　kidney；　Rene　Descartes；　who　did　more　than　anyone　else　to　help　men　to　realize　the　value　of　the　better　way　which　Harvey　had　pointed　out。　That　the　beginning　of　wisdom　was　in　doubt；　not　in　authority；　was　a　novel　doctrine　in　the　world；　but　Descartes　was　no　armchair　philosopher；　and　his　strong　advocacy　and　practice　of　experimentation　had　a　profound　influence　in　directing　men　to　〃la　nouvelle　methode。〃　　He　brought　the　human　body；　the　earthly　machine；　as　he　calls　it；　into　the　sphere　of　mechanics　and　physics；　and　he　wrote　the　first　text…book　of　physiology；　〃De　l'Homme。〃　Locke；　too；　became　the　spokesman　of　the　new　questioning　spirit；　and　before　the　close　of　the　seventeenth　century；　experimental　research　became　all　the　mode。　Richard　Lower；　Hooke　and　Hales　were　probably　more　influenced　by　Descartes　than　by　Harvey；　and　they　made　notable　contributions　to　experimental　physiology　in　England。　　Borelli；　author　of　the　famous　work　on　〃The　Motion　of　Animals〃　（Rome；　1680…1681）；　brought　to　the　study　of　the　action　of　muscles　a　profound　knowledge　of　physics　and　mathematics　and　really　founded　the　mechanical；　or　iatromechanical　school。　The　literature　and　the　language　of　medicine　became　that　of　physics　and　mechanics：　　wheels　and　pulleys；　wedges；　levers；　screws；　cords；　canals。　　cisterns；　sieves　and　strainers；　with　angles；　cylinders；　celerity；　percussion　and　resistance；　were　among　the　words　that　now　came　into　use　in　medical　literature。　Withington　quotes　a　good　example　in　a　description　by　Pitcairne；　the　Scot　who　was　professor　of　medicine　at　Leyden　at　the　end　of　the　seventeenth　century。　　〃Life　is　the　circulation　of　the　blood。　Health　is　its　free　and　painless　circulation。　　Disease　is　an　abnorm