a history of science-2-第58章

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es。　Hales　made　a　series　of　investigations　upon　animals　to　determine　the　force　of　the　blood　pressure；　and　similarly　he　made　numerous　statical　experiments　to　determine　the　pressure　of　the　flow　of　sap　in　vegetables。　His　Vegetable　Statics；　published　in　1727；　was　the　first　important　work　on　the　subject　of　vegetable　physiology；　and　for　this　reason　Hales　has　been　called　the　father　of　this　branch　of　science。　In　botany；　as　well　as　in　zoology；　the　classifications　of　Linnaeus　of　course　supplanted　all　preceding　classifications；　for　the　obvious　reason　that　they　were　much　more　satisfactory；　but　his　work　was　a　culmination　of　many　similar　and　more　or　less　satisfactory　attempts　of　his　predecessors。　About　the　year　1670　Dr。　Robert　Morison　（1620…1683）；　of　Aberdeen；　published　a　classification　of　plants；　his　system　taking　into　account　the　woody　or　herbaceous　structure；　as　well　as　the　flowers　and　fruit。　This　classification　was　supplanted　twelve　years　later　by　the　classification　of　Ray；　who　arranged　all　known　vegetables　into　thirty…three　classes；　the　basis　of　this　classification　being　the　fruit。　A　few　years　later　Rivinus；　a　professor　of　botany　in　the　University　of　Leipzig；　made　still　another　classification；　determining　the　distinguishing　character　chiefly　from　the　flower；　and　Camerarius　and　Tournefort　also　made　elaborate　classifications。　On　the　Continent　Tournefort's　classification　was　the　most　popular　until　the　time　of　Linnaeus；　his　systematic　arrangement　including　about　eight　thousand　species　of　plants；　arranged　chiefly　according　to　the　form　of　the　corolla。　Most　of　these　early　workers　gave　attention　to　both　vegetable　and　animal　kingdoms。　They　were　called　naturalists；　and　the　field　of　their　investigations　was　spoken　of　as　〃natural　history。〃　The　specialization　of　knowledge　had　not　reached　that　later　stage　in　which　botanist；　zoologist；　and　physiologist　felt　their　labors　to　be　sharply　divided。　Such　a　division　was　becoming　more　and　more　necessary　as　the　field　of　knowledge　extended；　but　it　did　not　become　imperative　until　long　after　the　time　of　Linnaeus。　That　naturalist　himself；　as　we　shall　see；　was　equally　distinguished　as　botanist　and　as　zoologist。　His　great　task　of　organizing　knowledge　was　applied　to　the　entire　range　of　living　things。　Carolus　Linnaeus　was　born　in　the　town　of　Rashult；　in　Sweden；　on　May　13；　1707。　As　a　child　he　showed　great　aptitude　in　learning　botanical　names；　and　remembering　facts　about　various　plants　as　told　him　by　his　father。　His　eagerness　for　knowledge　did　not　extend　to　the　ordinary　primary　studies；　however；　and；　aside　from　the　single　exception　of　the　study　of　physiology；　he　proved　himself　an　indifferent　pupil。　His　backwardness　was　a　sore　trial　to　his　father；　who　was　desirous　that　his　son　should　enter　the　ministry；　but　as　the　young　Linnaeus　showed　no　liking　for　that　calling；　and　as　he　had　acquitted　himself　well　in　his　study　of　physiology；　his　father　at　last　decided　to　allow　him　to　take　up　the　study　of　medicine。　Here　at　last　was　a　field　more　to　the　liking　of　the　boy；　who　soon　vied　with　the　best　of　his　fellow…students　for　first　honors。　Meanwhile　he　kept　steadily　at　work　in　his　study　of　natural　history；　acquiring　considerable　knowledge　of　ornithology；　entomology；　and　botany；　and　adding　continually　to　his　collection　of　botanical　specimens。　In　1729　his　botanical　knowledge　was　brought　to　the　attention　of　Olaf　Rudbeck；　professor　of　botany　in　the　University　of　Upsala；　by　a　short　paper　on　the　sexes　of　plants　which　Linnaeus　had　prepared。　Rudbeck　was　so　impressed　by　some　of　the　ideas　expressed　in　this　paper　that　he　appointed　the　author　as　his　assistant　the　following　year。　This　was　the　beginning　of　Linnaes's　career　as　a　botanist。　The　academic　gardens　were　thus　thrown　open　to　him；　and　he　found　time　at　his　disposal　for　pursuing　his　studies　between　lecture　hours　and　in　the　evenings。　It　was　at　this　time　that　he　began　the　preparation　of　his　work　the　Systema　naturae；　the　first　of　his　great　works；　containing　a　comprehensive　sketch　of　the　whole　field　of　natural　history。　When　this　work　was　published；　the　clearness　of　the　views　expressed　and　the　systematic　arrangement　of　the　various　classifications　excited　great　astonishment　and　admiration；　and　placed　Linaeus　at　once　in　the　foremost　rank　of　naturalists。　This　work　was　followed　shortly　by　other　publications；　mostly　on　botanical　subjects；　in　which；　among　other　things；　he　worked　out　in　detail　his　famous　〃system。〃　This　system　is　founded　on　the　sexes　of　plants；　and　is　usually　referred　to　as　an　〃artificial　method〃　of　classification　because　it　takes　into　account　only　a　few　marked　characters　of　plants；　without　uniting　them　by　more　general　natural　affinities。　At　the　present　time　it　is　considered　only　as　a　stepping…stone　to　the　〃natural〃　system；　but　at　the　time　of　its　promulgation　it　was　epoch…marking　in　its　directness　and　simplicity；　and　therefore　superiority；　over　any　existing　systems。　One　of　the　great　reforms　effected　by　Linnaeus　was　in　the　matter　of　scientific　terminology。　Technical　terms　are　absolutely　necessary　to　scientific　progress；　and　particularly　so　in　botany；　where　obscurity；　ambiguity；　or　prolixity　in　descriptions　are　fatally　misleading。　Linnaeus's　work　contains　something　like　a　thousand　terms；　whose　meanings　and　uses　are　carefully　explained。　Such　an　array　seems　at　first　glance　arbitrary　and　unnecessary；　but　the　fact　that　it　has　remained　in　use　for　something　like　two　centuries　is　indisputable　evidence　of　its　practicality。　The　descriptive　language　of　botany；　as　employed　by　Linnaeus；　still　stands　as　a　model　for　all　other　subjects。　Closely　allied　to　botanical　terminology　is　the　subject　of　botanical　nomenclature。　The　old　method　of　using　a　number　of　Latin　words　to　describe　each　different　plant　is　obviously　too　cumbersome；　and　several　attempts　had　been　made　prior　to　the　time　of　Linnaeus　to　substitute　simpler　methods。　Linnaeus　himself　made　several　unsatisfactory　attempts　before　he　finally　hit　upon　his　system　of　〃trivial　names；〃　which　was　developed　in　his　Species　plantarum；　and　which；　with　some；　minor　alterations；　remains　in　use　to　this　day。　The　essence　of　the　system　is　the　introduction　of　binomial　nomenclaturethat　is　to　say；　the　use　of　two　names　and　no　more　to　designate　any　single　species　of　animal　or　plant。　The　principle　is　quite　the　same　as　that　according　to　which　in　modern　society　a　man　has　two　names；　let　us　say；　John　Doe；　the　one　designating　his　family；　the　other　being　individual。　Similarly　each　species　of　animal　or　plant；　according　to　the　Linnaeean　system；　received　a　specific　or　〃trivial〃　name；　while　various　species；　associated　according　to　their　seeming　natural　affinities　into　groups　called　genera；　were　given　the　same　generic　name。　Thus　the　generic　name　given　all　members　of　the　cat　tribe　being　Felis；　the　name　Felis　leo　designates　the　lion；　Felis　pardus；　the　leopard；　Felis　domestica；　the　house　cat；　and　so　on。　This　seems　perfectly　simple　and　natural　now；　but　to　understand　how　great　a　reform　the　binomial　nomenclature　introduced　we　have　but　to　consult　the　work　of　Linnaeus's　predecessors。　A　single　illustration　will　suffice。　There　is；　for　example；　a　kind　of　grass；　in　referring　to　which　the　naturalist　anterior　to　Linnaeus；　if　he　would　be　absolutely　unambiguous；　was　obliged　to　use　the　following　descriptive　formula：　Gramen　Xerampelino；　Miliacea；　praetenuis　ramosaque　sparsa　panicula；　sive　Xerampelino　congener；　arvense；　aestivum；　gramen　minutissimo　semine。　Linnaeus　gave　to　this　plant　the　name　Poa　bulbosaa　name　that　sufficed；　according　to　the　new　system；　to　distinguish　this　from　every　other　species　of　vegetable。　It　does　not　require　any　special　knowledge　to　appreciate　the　advantage　of　such　a　simplification。　While　visiting　Paris　in　1738　Linnaeus　met　and　botanized　with　the　two　botanists　whose　〃natural　method〃　of　classification　was　later　to　supplant　his　own　〃artificial　system。〃　These　were　Bernard　and　Antoine　Laurent　de　Jussieu。　The　efforts　of　these　two　scientists　were　directed　towards　obtaining　a　system　which　should　aim　at　clearness；　simplicity；　and　precision；　and　at　the　same　time　be　governed　by　the　natural　affinities　of　plants。　The　natural　system；　as　finally　propounded　by　them；　is　based　on　the　number　of　cotyledons；　the　structure　of　the　seed；　and　the　insertion　of　the　stamens。　Succeeding　writers　on　botany　have　made　various　modif