a history of science-1-第42章

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way　the　sea　is　one；　do　not　assert　things　very　improbable。　They　confirm　this　conjecture　moreover　by　the　elephants；　which　are　said　to　be　of　the　same　species　towards　each　extreme；　as　if　this　circumstance　was　a　consequence　of　the　conjunction　of　the　extremes。　The　mathematicians　who　try　to　calculate　the　measure　of　the　circumference；　make　it　amount　to　four　hundred　thousand　stadia；　whence　we　collect　that　the　earth　is　not　only　spherical；　but　is　not　large　compared　with　the　magnitude　of　the　other　stars。〃　But　in　giving　full　meed　of　praise　to　Aristotle　for　the　promulgation　of　this　doctrine　of　the　sphericity　of　the　earth；　it　must　unfortunately　be　added　that　the　conservative　philosopher　paused　without　taking　one　other　important　step。　He　could　not　accept；　but；　on　the　contrary；　he　expressly　repudiated；　the　doctrine　of　the　earth's　motion。　We　have　seen　that　this　idea　also　was　a　part　of　the　Pythagorean　doctrine；　and　we　shall　have　occasion　to　dwell　more　at　length　on　this　point　in　a　succeeding　chapter。　It　has　even　been　contended　by　some　critics　that　it　was　the　adverse　conviction　of　the　Peripatetic　philosopher　which；　more　than　any　other　single　influence；　tended　to　retard　the　progress　of　the　true　doctrine　regarding　the　mechanism　of　the　heavens。　Aristotle　accepted　the　sphericity　of　the　earth；　and　that　doctrine　became　a　commonplace　of　scientific　knowledge；　and　so　continued　throughout　classical　antiquity。　But　Aristotle　rejected　the　doctrine　of　the　earth's　motion；　and　that　doctrine；　though　promulgated　actively　by　a　few　contemporaries　and　immediate　successors　of　the　Stagirite；　was　then　doomed　to　sink　out　of　view　for　more　than　a　thousand　years。　If　it　be　a　correct　assumption　that　the　influence　of　Aristotle　was；　in　a　large　measure；　responsible　for　this　result；　then　we　shall　perhaps　not　be　far　astray　in　assuming　that　the　great　founder　of　the　Peripatetic　school　was；　on　the　whole；　more　instrumental　in　retarding　the　progress　of　astronomical　science　that　any　other　one　man　that　ever　lived。　The　field　of　science　in　which　Aristotle　was　pre…eminently　a　pathfinder　is　zoology。　His　writings　on　natural　history　have　largely　been　preserved；　and　they　constitute　by　far　the　most　important　contribution　to　the　subject　that　has　come　down　to　us　from　antiquity。　They　show　us　that　Aristotle　had　gained　possession　of　the　widest　range　of　facts　regarding　the　animal　kingdom；　and；　what　is　far　more　important；　had　attempted　to　classify　these　facts。　In　so　doing　he　became　the　founder　of　systematic　zoology。　Aristotle's　classification　of　the　animal　kingdom　was　known　and　studied　throughout　the　Middle　Ages；　and；　in　fact；　remained　in　vogue　until　superseded　by　that　of　Cuvier　in　the　nineteenth　century。　It　is　not　to　be　supposed　that　all　the　terms　of　Aristotle's　classification　originated　with　him。　Some　of　the　divisions　are　too　patent　to　have　escaped　the　observation　of　his　predecessors。　Thus；　for　example；　the　distinction　between　birds　and　fishes　as　separate　classes　of　animals　is　so　obvious　that　it　must　appeal　to　a　child　or　to　a　savage。　But　the　efforts　of　Aristotle　extended；　as　we　shall　see；　to　less　patent　generalizations。　At　the　very　outset；　his　grand　division　of　the　animal　kingdom　into　blood…bearing　and　bloodless　animals　implies　a　very　broad　and　philosophical　conception　of　the　entire　animal　kingdom。　The　modern　physiologist　does　not　accept　the　classification；　inasmuch　as　it　is　now　known　that　colorless　fluids　perform　the　functions　of　blood　for　all　the　lower　organisms。　But　the　fact　remains　that　Aristotle's　grand　divisions　correspond　to　the　grand　divisions　of　the　Lamarckian　systemvertebrates　and　invertebrates　which　every　one　now　accepts。　Aristotle；　as　we　have　said；　based　his　classification　upon　observation　of　the　blood；　Lamarck　was　guided　by　a　study　of　the　skeleton。　The　fact　that　such　diverse　points　of　view　could　direct　the　observer　towards　the　same　result　gives；　inferentially；　a　suggestive　lesson　in　what　the　modern　physiologist　calls　the　homologies　of　parts　of　the　organism。　Aristotle　divides　his　so…called　blood…bearing　animals　into　five　classes：　（1）　Four…footed　animals　that　bring　forth　their　young　alive；　（2）　birds；　（3）　egg…laying　four…　footed　animals　（including　what　modern　naturalists　call　reptiles　and　amphibians）；　（4）　whales　and　their　allies；　（5）　fishes。　This　classification；　as　will　be　observed；　is　not　so　very　far　afield　from　the　modern　divisions　into　mammals；　birds；　reptiles；　amphibians；　and　fishes。　That　Aristotle　should　have　recognized　the　fundamental　distinction　between　fishes　and　the　fish…　like　whales；　dolphins；　and　porpoises　proves　the　far　from　superficial　character　of　his　studies。　Aristotle　knew　that　these　animals　breathe　by　means　of　lungs　and　that　they　produce　living　young。　He　recognized；　therefore；　their　affinity　with　his　first　class　of　animals；　even　if　he　did　not；　like　the　modern　naturalist；　consider　these　affinities　close　enough　to　justify　bringing　the　two　types　together　into　a　single　class。　The　bloodless　animals　were　also　divided　by　Aristotle　into　five　classesnamely：　（1）　Cephalopoda　（the　octopus；　cuttle…fish；　etc。）；　（2）　weak…shelled　animals　（crabs；　etc。）；　（3）　insects　and　their　allies　（including　various　forms；　such　as　spiders　and　centipedes；　which　the　modern　classifier　prefers　to　place　by　themselves）；　（4）　hard…shelled　animals　（clams；　oysters；　snails；　etc。）；　（5）　a　conglomerate　group　of　marine　forms；　including　star…fish；　sea…urchins；　and　various　anomalous　forms　that　were　regarded　as　linking　the　animal　to　the　vegetable　worlds。　This　classification　of　the　lower　forms　of　animal　life　continued　in　vogue　until　Cuvier　substituted　for　it　his　famous　grouping　into　articulates；　mollusks；　and　radiates；　which　grouping　in　turn　was　in　part　superseded　later　in　the　nineteenth　century。　What　Aristotle　did　for　the　animal　kingdom　his　pupil；　Theophrastus；　did　in　some　measure　for　the　vegetable　kingdom。　Theophrastus；　however；　was　much　less　a　classifier　than　his　master；　and　his　work　on　botany；　called　The　Natural　History　of　Development；　pays　comparatively　slight　attention　to　theoretical　questions。　It　deals　largely　with　such　practicalities　as　the　making　of　charcoal；　of　pitch；　and　of　resin；　and　the　effects　of　various　plants　on　the　animal　organism　when　taken　as　foods　or　as　medicines。　In　this　regard　the　work　of　Theophrastus；　is　more　nearly　akin　to　the　natural　history　of　the　famous　Roman　compiler；　Pliny。　It　remained；　however；　throughout　antiquity　as　the　most　important　work　on　its　subject；　and　it　entitles　Theophrastus　to　be　called　the　〃father　of　botany。〃　Theophrastus　deals　also　with　the　mineral　kingdom　after　much　the　same　fashion；　and　here　again　his　work　is　the　most　notable　that　was　produced　in　antiquity。

IX。　GREEK　SCIENCE　OF　THE　ALEXANDRIAN　OR　HELLENISTIC　PERIOD　We　are　entering　now　upon　the　most　important　scientific　epoch　of　antiquity。　When　Aristotle　and　Theophrastus　passed　from　the　scene；　Athens　ceased　to　be　in　any　sense　the　scientific　centre　of　the　world。　That　city　still　retained　its　reminiscent　glory；　and　cannot　be　ignored　in　the　history　of　culture；　but　no　great　scientific　leader　was　ever　again　to　be　born　or　to　take　up　his　permanent　abode　within　the　confines　of　Greece　proper。　With　almost　cataclysmic　suddenness；　a　new　intellectual　centre　appeared　on　the　south　shore　of　the　Mediterranean。　This　was　the　city　of　Alexandria；　a　city