autobiography and selected essays-第23部分

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

pause　or　sign　of　weakening。　　The　possible　complexity　of　many　other

organic　forms；　seemingly　as　simple　as　the　protoplasm　of　the　nettle；

dawns　upon　one；　and　the　comparison　of　such　a　protoplasm　to　a　body

with　an　internal　circulation；　which　has　been　put　forward　by　an

eminent　physiologist；　loses　much　of　its　startling　character。

Currents　similar　to　those　of　the　hairs　of　the　nettle　have　been

observed　in　a　great　multitude　of　very　different　plants；　and　weighty

authorities　have　suggested　that　they　probably　occur；　in　more　or

less　perfection；　in　all　young　vegetable　cells。　　If　such　be　the

case；　the　wonderful　noonday　silence　of　a　tropical　forest　is；　after

all；　due　only　to　the　dulness　of　our　hearing；　and　could　our　ears

catch　the　murmur　of　these　tiny　Maelstroms；　＇96＇　as　they　whirl　in　the

innumerable　myriads　of　living　cells　which　constitute　each　tree；　we

should　be　stunned；　as　with　the　roar　of　a　great　city。



Among　the　lower　plants；　it　is　the　rule　rather　than　the　exception；

that　contractility　should　be　still　more　openly　manifested　at　some

periods　of　their　existence。　　The　protoplasm　of　Algae　and　Fungi

becomes；　under　many　circumstances；　partially；　or　completely；　freed

from　its　woody　case；　and　exhibits　movements　of　its　whole　mass；　or

is　propelled　by　the　contractility　of　one；　or　more；　hair…like

prolongations　of　its　body；　which　are　called　vibratile　cilia。　　And；

so　far　as　the　conditions　of　the　manifestation　of　the　phaenomena　of

contractility　have　yet　been　studied；　they　are　the　same　for　the

plant　as　for　the　animal。　　Heat　and　electric　shocks　influence　both；

and　in　the　same　way；　though　it　may　be　in　different　degrees。　　It　is

by　no　means　my　intention　to　suggest　that　there　is　no　difference　in

faculty　between　the　lowest　plant　and　the　highest；　or　between　plants

and　animals。　　But　the　difference　between　the　powers　of　the　lowest

plant；　or　animal；　and　those　of　the　highest；　is　one　of　degree；　not

of　kind；　and　depends；　as　Milne…Edwards　＇97＇　long　ago　so　well　pointed

out；　upon　the　extent　to　which　the　principle　of　the　division　of

labour　is　carried　out　in　the　living　economy。　　In　the　lowest

organism　all　parts　are　competent　to　perform　all　functions；　and　one

and　the　same　portion　of　protoplasm　may　successfully　take　on　the

function　of　feeding；　moving；　or　reproducing　apparatus。　　In　the

highest；　on　the　contrary；　a　great　number　of　parts　combine　to

perform　each　function；　each　part　doing　its　allotted　share　of　the

work　with　great　accuracy　and　efficiency；　but　being　useless　for　any

other　purpose。



On　the　other　hand；　notwithstanding　all　the　fundamental　resemblances

which　exist　between　the　powers　of　the　protoplasm　in　plants　and　in

animals；　they　present　a　striking　difference　（to　which　I　shall

advert　more　at　length　presently）；　in　the　fact　that　plants　can

manufacture　fresh　protoplasm　out　of　mineral　compounds；　whereas

animals　are　obliged　to　procure　it　ready　made；　and　hence；　in　the

long　run；　depend　upon　plants。　　Upon　what　condition　this　difference

in　the　powers　of　the　two　great　divisions　of　the　world　of　life

depends；　nothing　is　at　present　known。



With　such　qualifications　as　arises　＇98＇　out　of　the　last…mentioned

fact；　it　may　be　truly　said　that　the　acts　of　all　living　things　are

fundamentally　one。　　Is　any　such　unity　predicable　of　their　forms？

Let　us　seek　in　easily　verified　facts　for　a　reply　to　this　question。

If　a　drop　of　blood　be　drawn　by　pricking　one's　finger；　and　viewed

with　proper　precautions；　and　under　a　sufficiently　high　microscopic

power；　there　will　be　seen；　among　the　innumerable　multitude　of

little；　circular；　discoidal　bodies；　or　corpuscles；　which　float　in

it　and　give　it　its　colour；　a　comparatively　small　number　of

colourless　corpuscles；　of　somewhat　larger　size　and　very　irregular

shape。　　If　the　drop　of　blood　be　kept　at　the　temperature　of　the

body；　these　colourless　corpuscles　will　be　seen　to　exhibit　a

marvellous　activity；　changing　their　forms　with　great　rapidity；

drawing　in　and　thrusting　out　prolongations　of　their　substance；　and

creeping　about　as　if　they　were　independent　organisms。



The　substance　which　is　thus　active　is　a　mass　of　protoplasm；　and　its

activity　differs　in　detail；　rather　than　in　principle；　from　that　of

the　protoplasm　of　the　nettle。　　Under　sundry　circumstances　the

corpuscle　dies　and　becomes　distended　into　a　round　mass；　in　the

midst　of　which　is　seen　a　smaller　spherical　body；　which　existed；　but

was　more　or　less　hidden；　in　the　living　corpuscle；　and　is　called　its

nucleus。　　Corpuscles　of　essentially　similar　structure　are　to　be

found　in　the　skin；　in　the　lining　of　the　mouth；　and　scattered

through　the　whole　framework　of　the　body。　　Nay；　more；　in　the

earliest　condition　of　the　human　organism；　in　that　state　in　which　it

has　but　just　become　distinguishable　from　the　egg　in　which　it

arises；　it　is　nothing　but　an　aggregation　of　such　corpuscles；　and

every　organ　of　the　body　was；　once；　no　more　than　such　an

aggregation。



Thus　a　nucleated　mass　of　protoplasm　turns　out　to　be　what　may　be

termed　the　structural　unit　of　the　human　body。　　As　a　matter　of　fact；

the　body；　in　its　earliest　state；　is　a　mere　multiple　of　such　units；

and　in　its　perfect　condition；　it　is　a　multiple　of　such　units；

variously　modified。



But　does　the　formula　which　expresses　the　essential　structural

character　of　the　highest　animal　cover　all　the　rest；　as　the

statement　of　its　powers　and　faculties　covered　that　of　all　others？

Very　nearly。　　Beast　and　fowl；　reptile　and　fish；　mollusk；　worm；　and

polype；　are　all　composed　of　structural　units　of　the　same　character；

namely；　masses　of　protoplasm　with　a　nucleus。　　There　are　sundry　very

low　animals；　each　of　which；　structurally；　is　a　mere　colourless

blood…corpuscle；　leading　an　independent　life。　　But；　at　the　very

bottom　of　the　animal　scale；　even　this　simplicity　becomes

simplified；　and　all　the　phaenomena　of　life　are　manifested　by　a

particle　of　protoplasm　without　a　nucleus。　　Nor　are　such　organisms

insignificant　by　reason　of　their　want　of　complexity。　　It　is　a　fair

question　whether　the　protoplasm　of　those　simplest　forms　of　life；

which　people　an　immense　extent　of　the　bottom　of　the　sea；　would　not

outweigh　that　of　all　the　higher　living　beings　which　inhabit　the

land　put　together。　　And　in　ancient　times；　no　less　than　at　the

present　day；　such　living　beings　as　these　have　been　the　greatest　of

rock　builders。



What　has　been　said　of　the　animal　world　is　no　less　true　of　plants。

Imbedded　in　the　protoplasm　at　the　broad；　or　attached；　end　of　the

nettle　hair；　there　lies　a　spheroidal　nucleus。　　Careful　examination

further　proves　that　the　whole　substance　of　the　nettle　is　made　up　of

a　repetition　of　such　masses　of　nucleated　protoplasm；　each　contained

in　a　wooden　case；　which　is　modified　in　form；　sometimes　into　a　woody

fibre；　sometimes　into　a　duct　or　spiral　vessel；　sometimes　into　a

pollen　grain；　or　an　ovule。　　Traced　back　to　its　earliest　state；　the

nettle　arises　as　the　man　does；　in　a　particle　of　nucleated

protoplasm。　　And　in　the　lowest　plants；　as　in　the　lowest　animals；　a

single　mass　of　such　protoplasm　may　constitute　the　whole　plant；　or

the　protoplasm　may　exist　without　a　nucleus。



Under　these　circumstances　it　may　well　be　asked；　how　is　one　mass　of

non…nucleated　protoplasm　to　be　distinguished　from　another？　why　call

one　〃plant〃　and　the　other　〃animal〃？



The　only　reply　is　that；　so　far　as　form　is　concerned；　plants　and

animals　are　not　separable；　and　that；　in　many　cases；　it　is　a　mere

matter　of　convention　whether　we　call　a　given　organism　an　animal　or

a　plant。　　There　is　a　living　body　called　Aethalium　septicum；　which

appears　upon　decaying　vegetable　substances；　and；　in　one　of　its

forms；　is　common　upon　the　surfaces　of　tan…pits。　　In　this　condition

it　is；　to　all　intents　and　purposes；　a　fungus；　and　formerly　was

always　regarded　as　such；　but　the　remarkable　investigations　of　De

Bary　＇99＇　have　shown　that；　in　another　condition；　the　Aethalium　is　an

actively　locomotive　creature；　and　takes　in　solid　matters；　upon

which；　apparently；　it　feeds；　thus　exhibiting　the　most　characteristic

feature　of　animality。　　Is　this　a　plant；　or　is　it　an　animal？

Is　it　both；　or　is　it　neither？　　Some　decide　in　favour　of　the　last

supposition；　and　establish　an　intermediate　kingdom；　a　sort

of　biological　No　Man's　Land　＇100＇　for　all　these　questionable　forms。

But；　as　it　is　admittedly　impossible　to　draw　any　distinct　boundary　line

between　this　no　man's　land　and　the　vegetable　world　on　the　one　hand；

or　the　animal；　on　the　other；　it　appears　to　me　that　this　proceeding

merely　doubles　the　difficulty　which；　before；　was　single。



Protoplasm；　simple　or　nucleated；　is　the　formal　basis　of　all　life。

It　is　the　clay　of　the　potter：　which；　bake　it　and　paint　it　as　he

will；　remains　clay；　separated　by　artifice；　and　not　by　nature；　from

the　commonest　brick　or　sun…dried　clod。



Thus　it　becomes　clear　that　all　living　powers　are　cognate；　and

that　all　living　forms　are　fundamentally　of　one　character。　　The

researches　of　the　chemist　have　revealed　a　no　less　striking

uniformity　of　material　composition　in　living　matter。



In　perfect　strictness；　it　is　true　that　chemical　investigation　can

tell　us　little　or　nothing；　directly；　of　the　composition　of　living

matter；　inasmuch　as　such　matter　must　needs　die　in　the　act　of

analysis；and　upon　this　very　obvious　ground；　objections；　which　I

confess　seem　to　me　to　be　somewhat　frivolous；　have　been　raised　to

the　drawing　of　any　conclusions　whatever　respecting　the　composition

of　actually　living　matter；　from　that　of　the　dead　matter　of　life；

which　alone　is　accessible　to　us。　　But　objectors　of　this　class　do

not　seem　to　reflect　that　it　is　also；　in　strictness；　true　that　we

know　nothing　about　the　composition　of　any　body　whatever；　as　it　is。

The　statement　that　a　crystal　of　calc…spar　consists　of　carbonate　of

lime；　is　quite　true；　if　we　only　mean　that；　by　appropriate

processes；　it　may　be　resolved　into　carbonic　acid　and　quicklime。　　If

you　pass　the　same　carbonic　acid　over　th