a history of science-1-第50章

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f　wine　with　pepper　sprinkled　on　it；　but　for　you　kings　we　only　use　the　safest　remedies；　and　it　will　suffice　to　apply　wool　soaked　in　hot　nard　ointment　locally。　The　emperor　ordered　the　wool；　wine；　etc。；　to　be　brought；　and　I　left　the　room。　His　feet　were　warmed　by　rubbing　with　hot　hands；　and　after　drinking　the　peppered　wine；　he　said　to　Pitholaus　（his　son's　tutor）；　'We　have　only　one　doctor；　and　that　an　honest　one；'　and　went　on　to　describe　me　as　the　first　of　physicians　and　the　only　philosopher；　for　he　had　tried　many　before　who　were　not　only　lovers　of　money；　but　also　contentious；　ambitious；　envious；　and　malignant。〃＇7＇　It　will　be　seen　from　this　that　Galen　had　a　full　appreciation　of　his　own　abilities　as　a　physician；　but　inasmuch　as　succeeding　generations　for　a　thousand　years　concurred　in　the　alleged　statement　made　by　Marcus　Aurelius　as　to　his　ability；　he　is　perhaps　excusable　for　his　open　avowal　of　his　belief　in　his　powers。　His　faith　in　his　accuracy　in　diagnosis　and　prognosis　was　shown　when　a　colleague　once　said　to　him；　〃I　have　used　the　prognostics　of　Hippocrates　as　well　as　you。　Why　can　I　not　prognosticate　as　well　as　you？〃　To　this　Galen　replied；　〃By　God's　help　I　have　never　been　deceived　in　my　prognosis。〃＇8＇　It　is　probable　that　this　statement　was　made　in　the　heat　of　argument；　and　it　is　hardly　to　be　supposed　that　he　meant　it　literally。　His　systems　of　treatment　were　far　in　advance　of　his　theories　regarding　the　functions　of　organs；　causes　of　disease；　etc。；　and　some　of　them　are　still　first　principles　with　physicians。　Like　Hippocrates；　he　laid　great　stress　on　correct　diet；　exercise；　and　reliance　upon　nature。　〃Nature　is　the　overseer　by　whom　health　is　supplied　to　the　sick；〃　he　says。　〃Nature　lends　her　aid　on　all　sides；　she　decides　and　cures　diseases。　No　one　can　be　saved　unless　nature　conquers　the　disease；　and　no　one　dies　unless　nature　succumbs。〃　From　the　picture　thus　drawn　of　Galen　as　an　anatomist　and　physician；　one　might　infer　that　he　should　rank　very　high　as　a　scientific　exponent　of　medicine；　even　in　comparison　with　modern　physicians。　There　is；　however；　another　side　to　the　picture。　His　knowledge　of　anatomy　was　certainly　very　considerable；　but　many　of　his　deductions　and　theories　as　to　the　functions　of　organs；　the　cause　of　diseases；　and　his　methods　of　treating　them；　would　be　recognized　as　absurd　by　a　modern　school…boy　of　average　intelligence。　His　greatness　must　be　judged　in　comparison　with　ancient；　not　with　modern；　scientists。　He　maintained；　for　example；　that　respiration　and　the　pulse…beat　were　for　one　and　the　same　purposethat　of　the　reception　of　air　into　the　arteries　of　the　body。　To　him　the　act　of　breathing　was　for　the　purpose　of　admitting　air　into　the　lungs；　whence　it　found　its　way　into　the　heart；　and　from　there　was　distributed　throughout　the　body　by　means　of　the　arteries。　The　skin　also　played　an　important　part　in　supplying　the　body　with　air；　the　pores　absorbing　the　air　and　distributing　it　through　the　arteries。　But；　as　we　know　that　he　was　aware　of　the　fact　that　the　arteries　also　contained　blood；　he　must　have　believed　that　these　vessels　contained　a　mixture　of　the　two。　Modern　anatomists　know　that　the　heart　is　divided　into　two　approximately　equal　parts　by　an　impermeable　septum　of　tough　fibres。　Yet；　Galen；　who　dissected　the　hearts　of　a　vast　number　of　the　lower　animals　according　to　his　own　account；　maintained　that　this　septum　was　permeable；　and　that　the　air；　entering　one　side　of　the　heart　from　the　lungs；　passed　through　it　into　the　opposite　side　and　was　then　transferred　to　the　arteries。　He　was　equally　at　fault；　although　perhaps　more　excusably　so；　in　his　explanation　of　the　action　of　the　nerves。　He　had　rightly　pointed　out　that　nerves　were　merely　connections　between　the　brain　and　spinal…cord　and　distant　muscles　and　organs；　and　had　recognized　that　there　were　two　kinds　of　nerves；　but　his　explanation　of　the　action　of　these　nerves　was　that　〃nervous　spirits〃　were　carried　to　the　cavities　of　the　brain　by　blood…vessels；　and　from　there　transmitted　through　the　body　along　the　nerve…trunks。　In　the　human　skull；　overlying　the　nasal　cavity；　there　are　two　thin　plates　of　bone　perforated　with　numerous　small　apertures。　These　apertures　allow　the　passage　of　numerous　nerve…filaments　which　extend　from　a　group　of　cells　in　the　brain　to　the　delicate　membranes　in　the　nasal　cavity。　These　perforations　in　the　bone；　therefore；　are　simply　to　allow　the　passage　of　the　nerves。　But　Galen　gave　a　very　different　explanation。　He　believed　that　impure　〃animal　spirits〃　were　carried　to　the　cavities　of　the　brain　by　the　arteries　in　the　neck　and　from　there　were　sifted　out　through　these　perforated　bones；　and　so　expelled　from　the　body。　He　had　observed　that　the　skin　played　an　important　part　in　cooling　the　body；　but　he　seems　to　have　believed　that　the　heart　was　equally　active　in　overheating　it。　The　skin；　therefore；　absorbed　air　for　the　purpose　of　〃cooling　the　heart；〃　and　this　cooling　process　was　aided　by　the　brain；　whose　secretions　aided　also　in　the　cooling　process。　The　heart　itself　was　the　seat　of　courage；　the　brain　the　seat　of　the　rational　soul；　and　the　liver　the　seat　of　love。　The　greatness　of　Galen's　teachings　lay　in　his　knowledge　of　anatomy　of　the　organs；　his　weakness　was　in　his　interpretations　of　their　functions。　Unfortunately；　succeeding　generations　of　physicians　for　something　like　a　thousand　years　rejected　the　former　but　clung　to　the　latter；　so　that　the　advances　he　had　made　were　completely　overshadowed　by　the　mistakes　of　his　teachings。

XI。　A　RETROSPECTIVE　GLANCE　AT　CLASSICAL　SCIENCE　It　is　a　favorite　tenet　of　the　modern　historian　that　history　is　a　continuous　stream。　The　contention　has　fullest　warrant。　Sharp　lines　of　demarcation　are　an　evidence　of　man's　analytical　propensity　rather　than　the　work　of　nature。　Nevertheless　it　would　be　absurd　to　deny　that　the　stream　of　history　presents　an　ever…varying　current。　There　are　times　when　it　seems　to　rush　rapidly　on；　times　when　it　spreads　out　into　a　broadseemingly　staticcurrent；　times　when　its　catastrophic　changes　remind　us　of　nothing　but　a　gigantic　cataract。　Rapids　and　whirlpools；　broad　estuaries　and　tumultuous　cataracts　are　indeed　part　of　the　same　stream；　but　they　are　parts　that　vary　one　from　another　in　their　salient　features　in　such　a　way　as　to　force　the　mind　to　classify　them　as　things　apart　and　give　them　individual　names。　So　it　is　with　the　stream　of　history；　however　strongly　we　insist　on　its　continuity　we　are　none　the　less　forced　to　recognize　its　periodicity。　It　may　not　be　desirable　to　fix　on　specific　dates　as　turning…points　to　the　extent　that　our　predecessors　were　wont　to　do。　We　may　not；　for　example；　be　disposed　to　admit　that　the　Roman　Empire　came　to　any　such　cataclysmic　finish　as　the　year　476　A。D。；　when　cited　in　connection　with　the　overthrow　of　the　last　Roman　Empire　of　the　West；　might　seem　to　indicate。　But；　on　the　other　hand；　no　student　of　the　period　can　fail　to　realize　that　a　great　change　came　over　the　aspect　of　the　historical　stream　towards　the　close　of　the　Roman　epoch。　The　span　from　Thales　to　Galen　has　compassed　about　eight　hundred　yearslet　us　say　thirty　generations。　Throughout　this　period　there　is　scarcely　a　generation　that　has　not　produced　great　scientific　thinkersmen　who　have　put　their　mark　upon　the　progress　of　civilization；　but　we　shall　see；　as　we　look　forward　for　a　corresponding　period；　that　the　ensuing　thirty　generations　produced　scarcely　a　single　scientific　thinker　of　the　first　rank。　Eight　hundred　years　of　intellectual　activity　thirty　generations　of　greatness；　then　eight　hundred　years　of　stasisthirty　generations　of　mediocrity；　such　seems　to　be　the　record　as　viewed　in　perspective。　Doubtless　it　seemed　far　different　to　the　contemporary　observer；　it　is　only　in　reasonable　perspective　that　any　scene　can　be　viewed　fairly。　But　for　us；　looking　back　without　prejudice　across　the　stage　of　years；　it　seems　indisputable　that　a　great　epoch　came　to　a　close　at　about　the　time　when　the　barbarian　nations　of　Europe　began　to　sweep　down　into　Greece　and　Italy。　We　are　forced　to　feel　that　we　have　reached　the　limits　of　progress　of　what　historians　are　pleased　to　call　the　ancient　world。　For　about　eight　hundred　years　Greek　thought　has　been　dominant；　but　in　the　ensuing　period　it　is　to　play　a　quite　subordinate　part；　except　in　so　far　as　it　influences　the　thought　of　an　alien　race。　As　we　leave　this　classical　epoch；　then；　we　may　well　recapitulate　in　brief　its　triumphs。　A　few　words　will　suffice　to　summarize　a　story　the　details　of　which　have　made　up　our　recent　chapters。　In　the　field　of　cosmology；　Greek　genius　has　demonstrated　that　the　earth　is　spheroidal；　that　the　moon　is　earthlike　in　structure　and　much　smaller　than　our　globe；　and　that　the　sun　is　vastly　larger　and　many　times　more　distant　than　the　moon。　The　actual　size　of　the　earth　and　the　angle　of　its　axis　with　the　ecliptic　have　been　measured　with　approximate　accuracy。　It　has　been　shown　that　the　sun　and　moon　present　inequalities　of　motion　which　may　be　theoretically　explained　by　supposing　that　the　earth　is　not　situated　precisely　at　the　centre　of　their　orbits。　A　system　of　eccentrics　and　epicycles　has　been　elaborated　which　serves　to　explain　the　apparent　motions　of　the　heavenly　bodies　in　a　manner　that　may　be　called　scientific　even　though　it　is　based；　as　we　now　know；　upon　a　false　hypothesis。　The　true　hypothesis；　which　places　the　sun　at　the　centre　o