autobiography and selected essays-第29章

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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　the　very　quicklime　thus

obtained；　you　will　obtain　carbonate　of　lime　again；　but　it　will　not

be　calc…spar；　nor　anything　like　it。　　Can　it；　therefore；　be　said

that　chemical　analysis　teaches　nothing　about　the　chemical

composition　of　calc…spar？　　Such　a　statement　would　be　absurd；　but　it

is　hardly　more　so　than　the　talk　one　occasionally　hears　about　the

uselessness　of　applying　the　results　of　chemical　analysis　to　the

living　bodies　which　have　yielded　them。



One　fact；　at　any　rate；　is　out　of　reach　of　such　refinements；　and

this　is；　that　all　the　forms　of　protoplasm　which　have　yet　been

examined　contain　the　four　elements；　carbon；　hydrogen；　oxygen；　and

nitrogen；　in　very　complex　union；　and　that　they　behave　similarly

towards　several　reagents。　　To　this　complex　combination；　the　nature

of　which　has　never　been　determined　with　exactness；　the　name　of

Protein　has　been　applied。　　And　if　we　use　this　term　with　such

caution　as　may　properly　arise　out　of　our　comparative　ignorance　of

the　things　for　which　it　stands；　it　may　be　truly　said；　that　all

protoplasm　is　proteinaceous；　or；　as　the　white；　or　albumen；　of　an

egg　is　one　of　the　commonest　examples　of　a　nearly　pure　proteine

matter；　we　may　say　that　all　living　matter　is　more　or　less

albuminoid。



Perhaps　it　would　not　yet　be　safe　to　say　that　all　forms　of

protoplasm　are　affected　by　the　direct　action　of　electric　shocks；

and　yet　the　number　of　cases　in　which　the　contraction　of　protoplasm

is　shown　to　be　affected　by　this　agency　increases　every　day。



Nor　can　it　be　affirmed　with　perfect　confidence；　that　all　forms　of

protoplasm　are　liable　to　undergo　that　peculiar　coagulation　at　a

temperature　of　40…50　degrees　centigrade；　which　has　been　called

〃heat…stiffening；〃　though　Kuhne's　＇101＇　beautiful　researches　have

proved　this　occurrence　to　take　place　in　so　many　and　such　diverse

living　beings；　that　it　is　hardly　rash　to　expect　that　the　law　holds

good　for　all。





Enough　has；　perhaps；　been　said　to　prove　the　existence　of　a　general

uniformity　in　the　chara