autobiography and selected essays-第22部分

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may　have　hypotheses；　and　hypotheses。　　A　man　may　say；　if　he　likes；

that　the　moon　is　made　of　green　cheese：　that　is　an　hypothesis。　　But

another　man；　who　has　devoted　a　great　deal　of　time　and　attention　to

the　subject；　and　availed　himself　of　the　most　powerful　telescopes

and　the　results　of　the　observations　of　others；　declares　that　in　his

opinion　it　is　probably　composed　of　materials　very　similar　to　those

of　which　our　own　earth　is　made　up：　and　that　is　also　only　an

hypothesis。　　But　I　need　not　tell　you　that　there　is　an　enormous

difference　in　the　value　of　the　two　hypotheses。　　That　one　which　is

based　on　sound　scientific　knowledge　is　sure　to　have　a　corresponding

value；　and　that　which　is　a　mere　hasty　random　guess　is　likely　to

have　but　little　value。　　Every　great　step　in　our　progress　in

discovering　causes　has　been　made　in　exactly　the　same　way　as　that

which　I　have　detailed　to　you。　　A　person　observing　the　occurrence　of

certain　facts　and　phenomena　asks；　naturally　enough；　what　process；

what　kind　of　operation　known　to　occur　in　Nature　applied　to　the

particular　case；　will　unravel　and　explain　the　mystery？　　Hence　you

have　the　scientific　hypothesis；　and　its　value　will　be　proportionate

to　the　care　and　completeness　with　which　its　basis　had　been　tested

and　verified。　　It　is　in　these　matters　as　in　the　commonest　affairs

of　practical　life：　the　guess　of　the　fool　will　be　folly；　while　the

guess　of　the　wise　man　will　contain　wisdom。　　In　all　cases；　you　see

that　the　value　of　the　result　depends　on　the　patience　and

faithfulness　with　which　the　investigator　applies　to　his　hypothesis

every　possible　kind　of　verification。







ON　THE　PHYSICAL　BASIS　OF　LIFE　＇92＇





In　order　to　make　the　title　of　this　discourse　generally

intelligible；　I　have　translated　the　term　〃Protoplasm；〃　which　is　the

scientific　name　of　the　substance　of　which　I　am　about　to　speak；　by

the　words　〃the　physical　basis　of　life。〃　　I　suppose　that；　to　many；

the　idea　that　there　is　such　a　thing　as　a　physical　basis；　or　matter；

of　life　may　be　novelso　widely　spread　is　the　conception　of　life　as

a　something　which　works　through　matter；　but　is　independent　of　it；

and　even　those　who　are　aware　that　matter　and　life　are　inseparably

connected；　may　not　be　prepared　for　the　conclusion　plainly　suggested

by　the　phrase；　〃THE　physical　basis　or　matter　of　life；〃　that　there

is　some　one　kind　of　matter　which　is　common　to　all　living　beings；

and　that　their　endless　diversities　are　bound　together　by　a

physical；　as　well　as　an　ideal；　unity。　　In　fact；　when　first

apprehended；　such　a　doctrine　as　this　appears　almost　shocking　to

common　sense。



What；　truly；　can　seem　to　be　more　obviously　different　from　one

another；　in　faculty；　in　form；　and　in　substance；　than　the　various

kinds　of　living　beings？　　What　community　of　faculty　can　there　be

between　the　bright…coloured　lichen；　which　so　nearly　resembles　a

mere　mineral　incrustation　of　the　bare　rock　on　which　it　grows；　and

the　painter；　to　whom　it　is　instinct　with　beauty；　or　the　botanist；

whom　it　feeds　with　knowledge？



Again；　think　of　the　microscopic　fungusa　mere　infinitesimal　ovoid

particle；　which　finds　space　and　duration　enough　to　multiply　into

countless　millions　in　the　body　of　a　living　fly；　and　then　of　the

wealth　of　foliage；　the　luxuriance　of　flower　and　fruit；　which　lies

between　this　bald　sketch　of　a　plant　and　the　giant　pine　of

California；　towering　to　the　dimensions　of　a　cathedral　spire；　or　the

Indian　fig；　which　covers　acres　with　its　profound　shadow；　and

endures　while　nations　and　empires　come　and　go　around　its　vast

circumference。　　Or；　turning　to　the　other　half　of　the　world　of　life；

picture　to　yourselves　the　great　Finner　whale；＇93＇　hugest　of　beasts

that　live；　or　have　lived；　disporting　his　eighty　or　ninety　feet　of　bone；

muscle　and　blubber；　with　easy　roll；　among　waves　in　which　the

stoutest　ship　that　ever　left　dockyard　would　flounder　hopelessly；

and　contrast　him　with　the　invisible　animalculesmere　gelatinous

specks；　multitudes　of　which　could；　in　fact；　dance　upon　the　point　of

a　needle　with　the　same　ease　as　the　angels　of　the　Schoolmen　could；

in　imagination。　　With　these　images　before　your　minds；　you　may　well

ask；　what　community　of　form；　or　structure；　is　there　between　the

animalcule　and　the　whale；　or　between　the　fungus　and　the　fig…tree？

And；　a　fortiori；＇94＇　between　all　four？



Finally；　if　we　regard　substance；　or　material　composition；　what

hidden　bond　can　connect　the　flower　which　a　girl　wears　in　her　hair

and　the　blood　which　courses　through　her　youthful　veins；　or；　what　is

there　in　common　between　the　dense　and　resisting　mass　of　the　oak；　or

the　strong　fabric　of　the　tortoise；　and　those　broad　disks　of　glassy

jelly　which　may　be　seen　pulsating　through　the　waters　of　a　calm　sea；

but　which　drain　away　to　mere　films　in　the　hand　which　raises　them

out　of　their　element？



Such　objections　as　these　must；　I　think；　arise　in　the　mind　of　every

one　who　ponders；　for　the　first　time；　upon　the　conception　of　a

single　physical　basis　of　life　underlying　all　the　diversities　of

vital　existence；　but　I　propose　to　demonstrate　to　you　that；

notwithstanding　these　apparent　difficulties；　a　threefold　unity

namely；　a　unity　of　power　or　faculty；　a　unity　of　form；　and　a　unity

of　substantial　compositiondoes　pervade　the　whole　living　world。





No　very　abstruse　argumentation　is　needed；　in　the　first　place　to

prove　that　the　powers；　or　faculties；　of　all　kinds　of　living　matter；

diverse　as　they　may　be　in　degree；　are　substantially　similar　in

kind。



Goethe　has　condensed　a　survey　of　all　powers　of　mankind　into　the

well…known　epigram：＇95＇



〃Warum　treibt　sich　das　Volk　so　und　schreit？　　Es　will　sich　ernahren

Kinder　zeugen；　und　die　nahren　so　gut　es　vermag。

。　　　　。　　　　。　　　　。　　　　。　　　　。　　　　。　　　　。　　　　。　　　　。　　　　。　　　　。　　　　。

Weiter　bringt　es　kein　Mensch；　stell'　er　sich　wie　er　auch　will。〃





In　physiological　language　this　means；　that　all　the　multifarious　and

complicated　activities　of　man　are　comprehensible　under　three

categories。　　Either　they　are　immediately　directed　towards　the

maintenance　and　development　of　the　body；　or　they　effect　transitory

changes　in　the　relative　positions　of　parts　of　the　body；　or　they

tend　towards　the　continuance　of　the　species。　　Even　those

manifestations　of　intellect；　of　feeling；　and　of　will；　which　we

rightly　name　the　higher　faculties；　are　not　excluded　from　this

classification；　inasmuch　as　to　every　one　but　the　subject　of　them；

they　are　known　only　as　transitory　changes　in　the　relative　positions

of　parts　of　the　body。　　Speech；　gesture；　and　every　other　form　of

human　action　are；　in　the　long　run；　resolvable　into　muscular

contraction；　and　muscular　contraction　is　but　a　transitory　change　in

the　relative　positions　of　the　parts　of　a　muscle。　　But　the　scheme

which　is　large　enough　to　embrace　the　activities　of　the　highest　form

of　life；　covers　all　those　of　the　lower　creatures。　　The　lowest

plant；　or　animalcule；　feeds；　grows；　and　reproduces　its　kind。　　In

addition；　all　animals　manifest　those　transitory　changes　of　form

which　we　class　under　irritability　and　contractility；　and；　it　is

more　than　probable；　that　when　the　vegetable　world　is　thoroughly

explored；　we　shall　find　all　plants　in　possession　of　the　same

powers；　at　one　time　or　other　of　their　existence。



I　am　not　now　alluding　to　such　phaenomena；　at　once　rare　and

conspicuous；　as　those　exhibited　by　the　leaflets　of　the　sensitive

plants；　or　the　stamens　of　the　barberry；　but　to　much　more　widely

spread；　and　at　the　same　time；　more　subtle　and　hidden；

manifestations　of　vegetable　contractility。　　You　are　doubtless　aware

that　the　common　nettle　owes　its　stinging　property　to　the

innumerable　stiff　and　needle…like；　though　exquisitely　delicate；

hairs　which　cover　its　surface。　　Each　stinging…needle　tapers　from　a

broad　base　to　a　slender　summit；　which；　though　rounded　at　the　end；

is　of　such　microscopic　fineness　that　it　readily　penetrates；　and

breaks　off　in；　the　skin。　　The　whole　hair　consists　of　a　very

delicate　outer　case　of　wood；　closely　applied　to　the　inner　surface

of　which　is　a　layer　of　semi…fluid　matter；　full　of　innumerable

granules　of　extreme　minuteness。　　This　semi…fluid　lining　is

protoplasm；　which　thus　constitutes　a　kind　of　bag；　full　of　a　limpid

liquid；　and　roughly　corresponding　in　form　with　the　interior　of　the

hair　which　it　fills。　　When　viewed　with　a　sufficiently　high

magnifying　power；　the　protoplasmic　layer　of　the　nettle　hair　is　seen

to　be　in　a　condition　of　unceasing　activity。　　Local　contractions　of

the　whole　thickness　of　its　substance　pass　slowly　and　gradually　from

point　to　point；　and　give　rise　to　the　appearance　of　progressive

waves；　just　as　the　bending　of　successive　stalks　of　corn　by　a　breeze

produces　the　apparent　billows　of　a　cornfield。



But；　in　addition　to　these　movements；　and　independently　of　them；　the

granules　are　driven；　in　relatively　rapid　streams；　through　channels

in　the　protoplasm　which　seem　to　have　a　considerable　amount　of

persistence。　　Most　commonly；　the　currents　in　adjacent　parts　of　the

protoplasm　take　similar　directions；　and；　thus；　there　is　a　general

stream　up　one　side　of　the　hair　and　down　the　other。　　But　this　does

not　prevent　the　existence　of　partial　currents　which　take　different

routes；　and　sometimes　trains　of　granules　may　be　seen　coursing

swiftly　in　opposite　directions　within　a　twenty…thousandth　of　an

inch　of　one　another；　while；　occasionally；　opposite　streams　come

into　direct　collision；　and；　after　a　longer　or　shorter　struggle；　one

predominates。　　The　cause　of　these　currents　seems　to　lie　in

contractions　of　the　protoplasm　which　bounds　the　channels　in　which

they　flow；　but　which　are　so　minute　that　the　best　microscopes　show

only　their　effects；　and　not　themselves。



The　spectacle　afforded　by　the　wonderful　energies　prisoned　within

the　compass　of　the　microscopic　hair　of　a　plant；　which　we　commonly

regard　as　a　merely　passive　organism；　is　not　easily　forgotten　by　one

who　has　watched　its　display；　continued　hour　after　hour；　without

pause　or　sign　of　weakening。　　The　p