On the Relations of Man to the Lower Animals小说第2章

第2章

　　grains，thisisequivalentto62cubicinchesofwater；sothatasbrainisheavierthanwater，weareperfectlysafeagainsterringonthesideofdiminutionintakingthisasthesmallestcapacityofanyadultmalehumanbrain。Theonlyadultmalebrain，weighingaslittleas970grammes，isthatofanidiot；butthebrainofanadultwoman，againstthesoundnessofwhosefacultiesnothingappears，weighedaslittleas907grammes（55。3cubicinchesofwater）；andReidgivesanadultfemalebrainofstillsmallercapacity。Theheaviestbrain（1872grammes，orabout115cubicinches）was，however，thatofawoman；nexttoitcomesthebrainofCuvier（1861grammes），thenByron（1807grammes），andthenaninsaneperson（1783grammes）。
　　Thelightestadultbrainrecorded（720grammes）wasthatofanidioticfemale。Thebrainsoffivechildren，fouryearsold，weighedbetween1275and992grammes。Sothatitmaybesafelysaid，thatanaverageEuropeanchildoffouryearsoldhasabraintwiceaslargeasthatofanadultGorilla。
　　Nodoubt，thisisaverystrikingdifference，butitlosesmuchofitsapparentsystematicvalue，whenviewedbythelightofcertainotherequallyindubitablefactsrespectingcranialcapacities。
　　Thefirstoftheseis，thatthedifferenceinthevolumeofthecranialcavityofdifferentracesofmankindisfargreater，absolutely，thanthatbetweenthelowestManandthehighestApe，while，relatively，itisaboutthesame。ForthelargesthumanskullmeasuredbyMortoncontained114cubicinches，thatistosay，hadverynearlydoublethecapacityofthesmallest；whileitsabsolutepreponderance，of52cubicinches——isfargreaterthanthatbywhichthelowestadultmalehumancraniumsurpassesthelargestoftheGorillas（62-34-1/2=27-1/2）。
　　Secondly，theadultcraniaofGorillaswhichhaveasyetbeenmeasureddifferamongthemselvesbynearlyone-third，themaximumcapacitybeing34。5cubicinches，theminimum24cubicinches；and，thirdly，aftermakingalldueallowancefordifferenceofsize，thecranialcapacitiesofsomeofthelowerApesfallnearlyasmuch，relatively，belowthoseofthehigherApesasthelatterfallbelowMan。
　　Thus，evenintheimportantmatterofcranialcapacity，MendiffermorewidelyfromoneanotherthantheydofromtheApes；whilethelowestApesdifferasmuch，inproportion，fromthehighest，asthelatterdoesfromMan。ThelastpropositionisstillbetterillustratedbythestudyofthemodificationswhichotherpartsofthecraniumundergointheSimianseries。
　　ItisthelargeproportionalsizeofthefacialbonesandthegreatprojectionofthejawswhichconfersupontheGorilla’sskullitssmallfacialangleandbrutalcharacter。
　　FIG。16。——SectionsoftheskullsofManandvariousApes，drawnsoastogivethecerebralcavitythesamelengthineachcase，therebydisplayingthevaryingproportionsofthefacialbones。Theline’b’
　　indicatestheplaneofthetentorium，whichseparatesthecerebrumfromthecerebellum；’d’，theaxisoftheoccipitaloutletoftheskull。Theextentofcerebralcavitybehind’c’，whichisaperpendicularerectedon’b’atthepointwherethetentoriumisattachedposteriorly，indicatesthedegreetowhichthecerebrumoverlapsthecerebellum——thespaceoccupiedbywhichisroughlyindicatedbythedarkshading。Incomparingthesediagrams，itmustberecollected，thatfiguresonsosmallascaleasthesesimplyexemplifythestatementsinthetext，theproofofwhichistobefoundintheobjectsthemselves。
　　Butifweconsidertheproportionalsizeofthefacialbonestotheskullproperonly，thelittle’Chrysothrix’（Fig。16）differsverywidelyfromtheGorilla，and，inthesameway，asMandoes；whiletheBaboons（’Cynocephalus’，Fig。16）exaggeratethegrossproportionsofthemuzzleofthegreatAnthropoid，sothatitsvisagelooksmildandhumanbycomparisonwiththeirs。ThedifferencebetweentheGorillaandtheBaboonisevengreaterthanitappearsatfirstsight；forthegreatfacialmassoftheformerislargelyduetoadownwarddevelopmentofthejaws；anessentiallyhumancharacter，superaddeduponthatalmostpurelyforward，essentiallybrutal，developmentofthesamepartswhichcharacterizestheBaboon，andyetmoreremarkablydistinguishestheLemur。
　　Similarly，theoccipitalforamenof’Mycetes’（Fig。16），andstillmoreoftheLemurs，issituatedcompletelyintheposteriorfaceoftheskull，orasmuchfurtherbackthanthatoftheGorilla，asthatoftheGorillaisfurtherbackthanthatofMan；while，asiftorenderpatentthefutilityoftheattempttobaseanybroadclassificatorydistinctiononsuchacharacter，thesamegroupofPlatyrhine，orAmericanmonkeys，towhichtheMycetesbelongs，containstheChrysothrix，whoseoccipitalforamenissituatedfarmoreforwardthaninanyotherape，andnearlyapproachesthepositionitholdsinMan。
　　Again，theOrang’sskullisasdevoidofexcessivelydevelopedsupraciliaryprominencesasaMan’s，thoughsomevarietiesexhibitgreatcrestselsewhere（Seepp。231，232）；andinsomeoftheCebineapesandinthe’Chrysothrix’，thecraniumisassmoothandroundedasthatofManhimself。
　　Whatistrueoftheseleadingcharacteristicsoftheskull，holdsgood，asmaybeimagined，ofallminorfeatures；sothatforeveryconstantdifferencebetweentheGorilla’sskullandtheMan’s，asimilarconstantdifferenceofthesameorder（thatistosay，consistinginexcessordefectofthesamequality）maybefoundbetweentheGorilla’sskullandthatofsomeotherape。Sothat，fortheskull，nolessthanfortheskeletoningeneral，thepropositionholdsgood，thatthedifferencesbetweenManandtheGorillaareofsmallervaluethanthosebetweentheGorillaandsomeotherApes。
　　Inconnectionwiththeskull，Imayspeakoftheteeth——organswhichhaveapeculiarclassificatoryvalue，andwhoseresemblancesanddifferencesofnumber，form，andsuccession，takenasawhole，areusuallyregardedasmoretrustworthyindicatorsofaffinitythananyothers。
　　FIG。17。——Lateralviews，ofthesamelength，oftheupperjawsofvariousPrimates。’i’，incisors；’c’，canines’’pm’，premolars；’m’，molars。AlineisdrawnthroughthefirstmolarofMan，’Gorilla’，’Cynocephalus’，and’Cebus’，andthegrindingsurfaceofthesecondmolarisshownineach，itsanteriorandinternalanglebeingjustabovethe’m’of’m2’。
　　Manisprovidedwithtwosetsofteeth——milkteethandpermanentteeth。
　　Theformerconsistoffourincisors，orcuttingteeth；twocanines，oreyeteeth；andfourmolars，orgrinders，ineachjaw——makingtwentyinall。Thelatter（Fig。17）comprisefourincisors，twocanines，foursmallgrinders，calledpremolarsorfalsemolars，andsixlargegrinders，ortruemolars，ineachjaw——makingthirty-twoinall。Theinternalincisorsarelargerthantheexternalpair，intheupperjaw，smallerthantheexternalpair，inthelowerjaw。Thecrownsoftheuppermolarsexhibitfourcusps，orblunt-pointedelevations，andaridgecrossesthecrownobliquely，fromtheinner，anteriorcusptotheouter，posteriorcusp（Fig。17m2）。Theanteriorlowermolarshavefivecusps，threeexternalandtwointernal。Thepremolarshavetwocusps，oneinternalandoneexternal，ofwhichtheouteristhehigher。
　　InalltheserespectsthedentitionoftheGorillamaybedescribedinthesametermsasthatofMan；butinothermattersitexhibitsmanyandimportantdifferences（Fig。17）。
　　Thustheteethofmanconstitutearegularandevenseries——withoutanybreakandwithoutanymarkedprojectionofonetoothabovetheleveloftherest；apeculiaritywhich，asCuvierlongagoshowed，issharedbynoothermammalsaveone——asdifferentacreaturefrommanascanwellbeimagined——namely，thelongextinct’Anoplotherium’。TheteethoftheGorilla，onthecontrary，exhibitabreak，orinterval，termedthe’diastema’，inbothjaws：infrontoftheeye-tooth，orbetweenitandtheouterincisor，intheupperjaw；behindtheeyetooth，orbetweenitandthefrontfalsemolar，inthelowerjaw。Intothisbreakintheseries，ineachjaw，fitsthecanineoftheoppositejaw；thesizeoftheeye-toothintheGorillabeingsogreatthatitprojects，likeatusk，farbeyondthegeneralleveloftheotherteeth。TherootsofthefalsemolarteethoftheGorilla，again，aremorecomplexthaninMan，andtheproportionalsizeofthemolarsisdifferent。TheGorillahasthecrownofthehindmostgrinderofthelowerjawmorecomplex，andtheorderoferuptionofthepermanentteethisdifferent；thepermanentcaninesmakingtheirappearancebeforethesecondandthirdmolarsinMan，andafterthemintheGorilla。
　　Thus，whiletheteethoftheGorillacloselyresemblethoseofManinnumber，kind，andinthegeneralpatternoftheircrowns，theyexhibitmarkeddifferencesfromthoseofManinsecondaryrespects，suchasrelativesize，numberoffangs，andorderofappearance。
　　But，iftheteethoftheGorillabecomparedwiththoseofanApe，nofurtherremovedfromitthana’Cynocephalus’，orBaboon，itwillbefoundthatdifferencesandresemblancesofthesameorderareeasilyobservable；butthatmanyofthepointsinwhichtheGorillaresemblesManarethoseinwhichitdiffersfromtheBaboon；whilevariousrespectsinwhichitdiffersfromManareexaggeratedinthe’Cynocephalus’。ThenumberandthenatureoftheteethremainthesameintheBaboonasintheGorillaandinMan。ButthepatternoftheBaboon’suppermolarsisquitedifferentfromthatdescribedabove（Fig。17），thecaninesareproportionallylongerandmoreknife-like；
　　theanteriorpremolarinthelowerjawisspeciallymodified；theposteriormolarofthelowerjawisstilllargerandmorecomplexthanintheGorilla。
　　Passingfromtheold-worldApestothoseofthenewworld，wemeetwithachangeofmuchgreaterimportancethananyofthese。Insuchagenusas’Cebus’，forexample（Fig。17），itwillbefoundthatwhileinsomesecondarypoints，suchastheprojectionofthecaninesandthediastema，theresemblancetothegreatapeispreserved；inotherandmostimportantrespects，thedentitionisextremelydifferent。Insteadof20teethinthemilkset，thereare24：insteadof32teethinthepermanentset，thereare36，thefalsemolarsbeingincreasedfromeighttotwelve。Andinform，thecrownsofthemolarsareveryunlikethoseoftheGorilla，anddifferfarmorewidelyfromthehumanpattern。
　　TheMarmosets，ontheotherhand，exhibitthesamenumberofteethasManandtheGorilla；but，notwithstandingthis，theirdentitionisverydifferent，fortheyhavefourmorefalsemolars，liketheotherAmericanmonkeys——butastheyhavefourfewertruemolars，thetotalremainsthesame。AndpassingfromtheAmericanapestotheLemurs，thedentitionbecomesstillmorecompletelyandessentiallydifferentfromthatoftheGorilla。Theincisorsbegintovarybothinnumberandinform。Themolarsacquire，moreandmore，amany-pointed，insectivorouscharacter，andinoneGenus，theAye-Aye（’Cheiromys’），thecaninesdisappear，andtheteethcompletelysimulatethoseofaRodent（Fig。17）。
　　Henceitisobviousthat，greatlyasthedentitionofthehighestApediffersfromthatofMan，itdiffersfarmorewidelyfromthatofthelowerandlowestApes。
　　Whateverpartoftheanimalfabric——whateverseriesofmuscles，whatevervisceramightbeselectedforcomparison——theresultwouldbethesame——thelowerApesandtheGorillawoulddiffermorethantheGorillaandtheMan。Icannotattemptinthisplacetofollowoutallthesecomparisonsindetail，andindeeditisunnecessaryIshoulddoso。Butcertainreal，orsupposed，structuraldistinctionsbetweenmanandtheapesremain，uponwhichsomuchstresshasbeenlaid，thattheyrequirecarefulconsideration，inorderthatthetruevaluemaybeassignedtothosewhicharereal，andtheemptinessofthosewhicharefictitiousmaybeexposed。Irefertothecharactersofthehand，thefoot，andthebrain。
　　Manhasbeendefinedastheonlyanimalpossessedoftwohandsterminatinghisforelimbs，andoftwofeetendinghishindlimbs，whileithasbeensaidthatalltheapespossessfourhands；andhehasbeenaffirmedtodifferfundamentallyfromalltheapesinthecharactersofhisbrain，whichalone，ithasbeenstrangelyassertedandre-asserted，exhibitsthestructuresknowntoanatomistsastheposteriorlobe，theposteriorcornuofthelateralventricle，andthehippocampusminor。
　　Thattheformerpropositionshouldhavegainedgeneralacceptanceisnotsurprising——indeed，atfirstsight，appearancesaremuchinitsfavour：
　　but，asforthesecond，onecanonlyadmirethesurpassingcourageofitsenunciator，seeingthatitisaninnovationwhichisnotonlyopposedtogenerallyandjustlyaccepteddoctrines，butwhichisdirectlynegativedbythetestimonyofalloriginalinquirers，whohavespeciallyinvestigatedthematter：andthatitneitherhasbeen，norcanbe，supportedbyasingleanatomicalpreparation。Itwould，infact，beunworthyofseriousrefutation，exceptforthegeneralandnaturalbeliefthatdeliberateandreiteratedassertionsmusthavesomefoundation。
　　Beforewecandiscussthefirstpointwithadvantagewemustconsiderwithsomeattention，andcomparetogether，thestructureofthehumanhandandthatofthehumanfoot，sothatwemayhavedistinctandclearideasofwhatconstitutesahandandwhatafoot。
　　Theexternalformofthehumanhandisfamiliarenoughtoeveryone。Itconsistsofastoutwristfollowedbyabroadpalm，formedofflesh，andtendons，andskin，bindingtogetherfourbones，anddividingintofourlongandflexibledigits，orfingers，eachofwhichbearsonthebackofitslastjointabroadandflattenednail。Thelongestcleftbetweenanytwodigitsisratherlessthanhalfaslongasthehand。
　　Fromtheoutersideofthebaseofthepalmastoutdigitgoesoff，havingonlytwojointsinsteadofthree；soshort，thatitonlyreachestoalittlebeyondthemiddleofthefirstjointofthefingernextit；
　　andfurtherremarkablebyitsgreatmobility，inconsequenceofwhichitcanbedirectedoutwards，almostatarightangletotherest。Thisdigitiscalledthe’pollex，’orthumb；and，liketheothers，itbearsaflatnailuponthebackofitsterminaljoint。Inconsequenceoftheproportionsandmobilityofthethumb，itiswhatistermed"opposable"；inotherwords，itsextremitycan，withthegreatestease，bebroughtintocontactwiththeextremitiesofanyofthefingers；apropertyuponwhichthepossibilityofourcarryingintoeffecttheconceptionsofthemindsolargelydepends。
　　Theexternalformofthefootdifferswidelyfromthatofthehand；andyet，whencloselycompared，thetwopresentsomesingularresemblances。Thustheanklecorrespondsinamannerwiththewrist；
　　thesolewiththepalm；thetoeswiththefingers；thegreattoewiththethumb。Butthetoes，ordigitsofthefoot，arefarshorterinproportionthanthedigitsofthehand，andarelessmoveable，thewantofmobilitybeingmoststrikinginthegreattoe——which，again，isverymuchlargerinproportiontotheothertoesthanthethumbtothefingers。Inconsideringthispoint，however，itmustnotbeforgottenthatthecivilizedgreattoe，confinedandcrampedfromchildhoodupwards，isseentoagreatdisadvantage，andthatinuncivilizedandbarefootedpeopleitretainsagreatamountofmobility，andevensomesortofopposability。TheChineseboatmenaresaidtobeabletopullanoar；theartisansofBengaltoweave，andtheCarajastostealfishhooks，byitshelp；though，afterall，itmustberecollectedthatthestructureofitsjointsandthearrangementofitsbones，necessarilyrenderitsprehensileactionfarlessperfectthanthatofthethumb。
　　Buttogainapreciseconceptionoftheresemblancesanddifferencesofthehandandfoot，andofthedistinctivecharactersofeach，wemustlookbelowtheskin，andcomparethebonyframeworkanditsmotorapparatusineach（Fig。18）。
　　FIG。18-TheskeletonoftheHandandFootofManreducedfromDr。
　　Carter’sdrawingsinGray’s’Anatomy。’Thehandisdrawntoalargerscalethanthefoot。Theline’aa’inthehandindicatestheboundarybetweenthecarpusandthemetacarpus；’bb’thatbetweenthelatterandtheproximalphalanges；’cc’markstheendsofthedistalphalanges。Theline"a’a’"inthefootindicatestheboundarybetweenthetarsusandmetatarsus；"b’b’"marksthatbetweenthemetatarsusandtheproximalphalanges；and"c’c’"boundstheendsofthedistalphalanges；’ca’，thecalcaneum；’as’，theastragalus；’sc’，thescaphoidboneinthetarsus。
　　Theskeletonofthehandexhibits，intheregionwhichwetermthewrist，andwhichistechnicallycalledthe’carpus’——tworowsofcloselyfittedpolygonalbones，fourineachrow，whicharetolerablyequalinsize。Thebonesofthefirstrowwiththebonesoftheforearm，formthewristjoint，andarearrangedsidebyside，noonegreatlyexceedingoroverlappingtherest。
　　Thefourbonesofthesecondrowofthecarpusbearthefourlongboneswhichsupportthepalmofthehand。Thefifthboneofthesamecharacterisarticulatedinamuchmorefreeandmoveablemannerthantheothers，withitscarpalbone，andformsthebaseofthethumb。
　　Thesearecalled’metacarpal’bones，andtheycarrythe’phalanges’，orbonesofthedigits，ofwhichtherearetwointhethumb，andthreeineachofthefingers。
　　Theskeletonofthefootisverylikethatofthehandinsomerespects。
　　Thustherearethreephalangesineachofthelessertoes，andonlytwointhegreattoe，whichanswerstothethumb。Thereisalongbone，termed’metatarsal’，answeringtothemetacarpal，foreachdigit；andthe’tarsus’，whichcorrespondswiththecarpus，presentsfourshortpolygonalbonesinarow，whichcorrespondverycloselywiththefourcarpalbonesofthesecondrowofthehand。Inotherrespectsthefootdiffersverywidelyfromthehand。Thusthegreattoeisthelongestdigitbutone；anditsmetatarsalisfarlessmoveablyarticulatedwiththetarsus，thanthemetacarpalofthethumbwiththecarpus。Butafarmoreimportantdistinctionliesinthefactthat，insteadoffourmoretarsalbonesthereareonlythree；and，thatthesethreearenotarrangedsidebyside，orinonerow。Oneofthem，the’oscalcis’orheelbone（’ca’），liesexternally，andsendsbackthelargeprojectingheel；another，the’astragalus’（’as’），restsonthisbyoneface，andbyanother，forms，withthebonesoftheleg，theanklejoint；whileathirdface，directedforwards，isseparatedfromthethreeinnertarsalbonesoftherownextthemetatarsusbyabonecalledthe’scaphoid’
　　（’sc’）。
　　Thusthereisafundamentaldifferenceinthestructureofthefootandthehand，observablewhenthecarpusandthetarsusarecontrasted；andtherearedifferencesofdegreenoticeablewhentheproportionsandthemobilityofthemetacarpalsandmetatarsals，withtheirrespectivedigits，arecomparedtogether。
　　Thesametwoclassesofdifferencesbecomeobviouswhenthemusclesofthehandarecomparedwiththoseofthefoot。
　　Threeprincipalsetsofmuscles，called"flexors，"bendthefingersandthumb，asinclenchingthefist，andthreesets——theextensors——extendthem，asinstraighteningthefingers。Thesemusclesareall"longmuscles"；thatistosay，thefleshypartofeach，lyinginandbeingfixedtothebonesofthearm，is，attheotherend，continuedintotendons，orroundedcords，whichpassintothehand，andareultimatelyfixedtotheboneswhicharetobemoved。Thus，whenthefingersarebent，thefleshypartsoftheflexorsofthefingers，placedinthearm，contract，invirtueoftheirpeculiarendowmentasmuscles；andpullingthetendinouscords，connectedwiththeirends，causethemtopulldownthebonesofthefingerstowardsthepalm。
　　Notonlyaretheprincipalflexorsofthefingersandofthethumblongmuscles，buttheyremainquitedistinctfromoneanotherthroughtheirwholelength。
　　Inthefoot，therearealsothreeprincipalflexormusclesofthedigitsortoes，andthreeprincipalextensors；butoneextensorandoneflexorareshortmuscles；thatistosay，theirfleshypartsarenotsituatedintheleg（whichcorrespondswiththearm），butinthebackandinthesoleofthefoot——regionswhichcorrespondwiththebackandthepalmofthehand。
　　Again，thetendonsofthelongflexorofthetoes，andofthelongflexorofthegreattoe，whentheyreachthesoleofthefoot，donotremaindistinctfromoneanother，astheflexorsinthepalmofthehanddo，buttheybecomeunitedandcommingledinaverycuriousmanner——whiletheirunitedtendonsreceiveanaccessorymuscleconnectedwiththeheel-bone。
　　Butperhapsthemostabsolutelydistinctivecharacteraboutthemusclesofthefootistheexistenceofwhatistermedthe’peronaeuslongus’，alongmusclefixedtotheouterboneoftheleg，andsendingitstendontotheouterankle，behindandbelowwhichitpasses，andthencrossesthefootobliquelytobeattachedtothebaseofthegreattoe。
　　Nomuscleinthehandexactlycorrespondswiththis，whichiseminentlyafootmuscle。
　　Toresume——thefootofmanisdistinguishedfromhishandbythefollowingabsoluteanatomicaldifferences：——
　　1。Bythearrangementofthetarsalbones。
　　2。Byhavingashortflexorandashortextensormuscleofthedigits。
　　3。Bypossessingthemuscletermed’peronaeuslongus’。
　　Andifwedesiretoascertainwhethertheterminaldivisionofalimb，inotherPrimates，istobecalledafootorahand，itisbythepresenceorabsenceofthesecharactersthatwemustbeguided，andnotbythemereproportionsandgreaterorlessermobilityofthegreattoe，whichmayvaryindefinitelywithoutanyfundamentalalterationinthestructureofthefoot。
　　Keepingtheseconsiderationsinmind，letusnowturntothelimbsoftheGorilla。Theterminaldivisionoftheforelimbpresentsnodifficulty——boneforboneandmuscleformuscle，arefoundtobearrangedessentiallyasinman，orwithsuchminordifferencesasarefoundasvarietiesinman。TheGorilla’shandisclumsier，heavier，andhasathumbsomewhatshorterinproportionthanthatofman；butnoonehaseverdoubteditsbeingatruehand。
　　FIG19。——FootofMan，Gorilla，andOrang-Utanofthesameabsolutelength，toshowthedifferencesinproportionofeach。LettersasinFig。18。ReducedfromoriginaldrawingsbyMr。WaterhouseHawkins。
　　Atfirstsight，theterminationofthehindlimboftheGorillalooksveryhand-like，andasitisstillmoresoinmanyofthelowerapes，itisnotwonderfulthattheappellation"Quadrumana，"orfour-handedcreatures，adoptedfromtheolderanatomists*byBlumenbach，andunfortunatelyrenderedcurrentbyCuvier，shouldhavegainedsuchwideacceptanceasanamefortheSimiangroup。Butthemostcursoryanatomicalinvestigationatonceprovesthattheresemblanceoftheso-called"hindhand"toatruehand，isonlyskindeep，andthat，inallessentialrespects，thehindlimboftheGorillaisastrulyterminatedbyafootasthatofman。Thetarsalbones，inallimportantcircumstancesofnumber，disposition，andform，resemblethoseofman（Fig。19）。Themetatarsalsanddigits，ontheotherhand，areproportionallylongerandmoreslender，whilethegreattoeisnotonlyproportionallyshorterandweaker，butitsmetatarsalboneisunitedbyamoremoveablejointwiththetarsus。Atthesametime，thefootissetmoreobliquelyuponthelegthaninman。
　　{Footnote}*Inspeakingofthefootofhis"Pygmie，"Tysonremarks，p。
　　13：——"Butthispartintheformationandinitsfunctiontoo，beinglikeraHandthanaFoot：forthedistinguishingthissortofanimalsfromothers，IhavethoughtwhetheritmightnotbereckonedandcalledratherQuadru-manusthanQuadrupes，’i。e。’afour-handedratherthanafour-footedanimal。"
　　Asthispassagewaspublishedin1699，M。I。G。St。Hilaireisclearlyinerrorinascribingtheinventionoftheterm"quadrumanous"toBuffon，though"himanous"maybelongtohim。Tysonuses"Quadrumanus"
　　inseveralplaces，asatp。91……"Our’Pygmie’isnoMan，noryetthe’commonApe’，butasortof’Animal’betweenboth；andthougha’Biped’，yetofthe’Quadrumanus’-kind：thoughsome’Men’toohavebeenobservedtousetheir’Feet’like’Hands’，asIhaveseenseveral。"
　　Astothemuscles，thereisashortflexor，ashortextensor，anda’peronaeuslongus’，whilethetendonsofthelongflexorsofthegreattoeandoftheothertoesareunitedtogetherandwithanaccessoryfleshybundle。
　　ThehindlimboftheGorilla，therefore，endsinatruefoot，withaverymoveablegreattoe。Itisaprehensilefoot，indeed，butisinnosenseahand：itisafootwhichdiffersfromthatofmannotinanyfundamentalcharacter，butinmereproportions，inthedegreeofmobility，andinthesecondaryarrangementofitsparts。
　　Itmustnotbesupposed，however，becauseIspeakofthesedifferencesasnotfundamental，thatIwishtounderratetheirvalue。Theyareimportantenoughintheirway，thestructureofthefootbeinginstrictcorrelationwiththatoftherestoftheorganismineachcase。
　　NorcanitbedoubtedthatthegreaterdivisionofphysiologicallabourinMan，sothatthefunctionofsupportisthrownwhollyonthelegandfoot，isanadvanceinorganizationofverygreatmomenttohim；but，afterall，regardedanatomically，theresemblancesbetweenthefootofManandthefootoftheGorillaarefarmorestrikingandimportantthanthedifferences。
　　Ihavedweltuponthispointatlength，becauseitisoneregardingwhichmuchdelusionprevails；butImighthavepasseditoverwithoutdetrimenttomyargument，whichonlyrequiresmetoshowthat，bethedifferencesbetweenthehandandfootofManandthoseoftheGorillawhattheymay——thedifferencesbetweenthoseoftheGorilla，andthoseofthelowerApesaremuchgreater。
　　ItisnotnecessarytodescendlowerinthescalethantheOrangforconclusiveevidenceonthishead。
　　ThethumboftheOrangdiffersmorefromthatoftheGorillathanthethumboftheGorilladiffersfromthatofMan，notonlybyitsshortness，butbytheabsenceofanyspeciallongflexormuscle。ThecarpusoftheOrang，likethatofmostlowerapes，containsninebones，whileintheGorilla，asinManandtheChimpanzee，thereareonlyeight。
　　TheOrang’sfoot（Fig。19）isstillmoreaberrant；itsverylongtoesandshorttarsus，shortgreattoe，shortandraisedheel，greatobliquityofarticulationintheleg，andabsenceofalongflexortendontothegreattoe，separatingitfarmorewidelyfromthefootoftheGorillathanthelatterisseparatedfromthatofMan。
　　But，insomeofthelowerapes，thehandandfootdivergestillmorefromthoseoftheGorilla，thantheydointheOrang。ThethumbceasestobeopposableintheAmericanmonkeys；isreducedtoamererudimentcoveredbytheskinintheSpiderMonkey；andisdirectedforwardsandarmedwithacurvedclawliketheotherdigits，intheMarmosets——sothat，inallthesecases，therecanbenodoubtbutthatthehandismoredifferentfromthatoftheGorillathantheGorilla’shandisfromMan’s。
　　Andastothefoot，thegreattoeoftheMarmosetisstillmoreinsignificantinproportionthanthatoftheOrang——whileintheLemursitisverylarge，andascompletelythumb-likeandopposableasintheGorilla——butintheseanimalsthesecondtoeisoftenirregularlymodified，andinsomespeciesthetwoprincipalbonesofthetarsus，the’astragalus’andthe’oscalcis’，aresoimmenselyelongatedastorenderthefoot，sofar，totallyunlikethatofanyothermammal。
　　Sowithregardtothemuscles。TheshortflexorofthetoesoftheGorilladiffersfromthatofManbythecircumstancethatoneslipofthemuscleisattached，nottotheheelbone，buttothetendonsofthelongflexors。ThelowerApesdepartfromtheGorillabyanexaggerationofthesamecharacter，two，three，ormore，slipsbecomingfixedtothelongflexortendons——orbyamultiplicationoftheslips。——Again，theGorilladiffersslightlyfromManinthemodeofinterlacingofthelongflexortendons：andthelowerapesdifferfromtheGorillainexhibitingyetother，sometimesverycomplex，arrangementsofthesameparts，andoccasionallyintheabsenceoftheaccessoryfleshybundle。
　　Throughoutallthesemodificationsitmustberecollectedthatthefootlosesnooneofitsessentialcharacters。EveryMonkeyandLemurexhibitsthecharacteristicarrangementoftarsalbones，possessesashortflexorandshortextensormuscle，anda’peronaeuslongus’。
　　Variedastheproportionsandappearanceoftheorganmaybe，theterminaldivisionofthehindlimbremains，inplanandprincipleofconstruction，afoot，andnever，inthoserespects，canbeconfoundedwithahand。
　　Hardlyanypartofthebodilyframe，then，couldbefoundbettercalculatedtoillustratethetruththatthestructuraldifferencesbetweenManandthehighestApeareoflessvaluethanthosebetweenthehighestandthelowerApes，thanthehandorthefoot，andyet，perhaps，thereisoneorganthestudyofwhichenforcesthesameconclusioninastillmorestrikingmanner——andthatistheBrain。
　　ButbeforeenteringupontheprecisequestionoftheamountofdifferencebetweentheApe’sbrainandthatofMan，itisnecessarythatweshouldclearlyunderstandwhatconstitutesagreat，andwhatasmalldifferenceincerebralstructure；andweshallbebestenabledtodothisbyabriefstudyofthechiefmodificationswhichthebrainexhibitsintheseriesofvertebrateanimals。
　　Thebrainofafishisverysmall，comparedwiththespinalcordintowhichitiscontinued，andwiththenerveswhichcomeofffromit：ofthesegmentsofwhichitiscomposed——theolfactorylobes，thecerebralhemisphere，andthesucceedingdivisions——noonepredominatessomuchovertherestastoobscureorcoverthem；andtheso-calledopticlobesare，frequently，thelargestmassesofall。InReptiles，themassofthebrain，relativelytothespinalcord，increasesandthecerebralhemispheresbegintopredominateovertheotherparts；whileinBirdsthispredominanceisstillmoremarked。ThebrainofthelowestMammals，suchastheduck-billedPlatypusandtheOpossumsandKangaroos，exhibitsastillmoredefiniteadvanceinthesamedirection。Thecerebralhemisphereshavenowsomuchincreasedinsizeas，moreorless，tohidetherepresentativesoftheopticlobes，whichremaincomparativelysmall，sothatthebrainofaMarsupialisextremelydifferentfromthatofaBird，Reptile，orFish。Astephigherinthescale，amongtheplacentalMammals，thestructureofthebrainacquiresavastmodification——notthatitappearsmuchalteredexternally，inaRatorinaRabbit，fromwhatitisinaMarsupial——northattheproportionsofitspartsaremuchchanged，butanapparentlynewstructureisfoundbetweenthecerebralhemispheres，connectingthemtogether，aswhatiscalledthe’greatcommissure’or’corpuscallosum。’Thesubjectrequirescarefulre-investigation，butifthecurrentlyreceivedstatementsarecorrect，theappearanceofthe’corpuscallosum’intheplacentalmammalsisthegreatestandmostsuddenmodificationexhibitedbythebraininthewholeseriesofvertebratedanimals——itisthegreatestleapanywheremadebyNatureinherbrainwork。Forthetwohalvesofthebrainbeingoncethusknittogether，theprogressofcerebralcomplexityistraceablethroughacompleteseriesofstepsfromthelowestRodent，orInsectivore，toMan；andthatcomplexityconsists，chiefly，inthedisproportionatedevelopmentofthecerebralhemispheresandofthecerebellum，butespeciallyoftheformer，inrespecttotheotherpartsofthebrain。
　　Inthelowerplacentalmammals，thecerebralhemispheresleavetheproperupperandposteriorfaceofthecerebellumcompletelyvisible，whenthebrainisviewedfromabove；but，inthehigherforms，thehinderpartofeachhemisphere，separatedonlybythetentorium（p。
　　281）fromtheanteriorfaceofthecerebellum，inclinesbackwardsanddownwards，andgrowsout，astheso-called"posteriorlobe，"soasatlengthtooverlapandhidethecerebellum。InallMammals，eachcerebralhemispherecontainsacavitywhichistermedthe’ventricle，’
　　andasthisventricleisprolonged，ontheonehand，forwards，andontheotherdownwards，intothesubstanceofthehemisphere，itissaidtohavetwohornsor’cornua，an’anteriorcornu，’anda’descendingcornu。’Whentheposteriorlobeiswelldeveloped，athirdprolongationoftheventricularcavityextendsintoit，andiscalledthe"posteriorcornu。"
　　InthelowerandsmallerformsofplacentalMammalsthesurfaceofthecerebralhemispheresiseithersmoothorevenlyrounded，orexhibitsaveryfewgrooves，whicharetechnicallytermed’sulci，’separatingridgesor’convolutions’ofthesubstanceofthebrain；andthesmallerspeciesofallorderstendtoasimilarsmoothnessofbrain。But，inthehigherorders，andespeciallythelargermembersoftheseorders，thegrooves，orsulci，becomeextremelynumerous，andtheintermediateconvolutionsproportionatelymorecomplicatedintheirmeanderings，until，intheElephant，thePorpoise，thehigherApes，andMan，thecerebralsurfaceappearsaperfectlabyrinthoftortuousfoldings。
　　Whereaposteriorlobeexistsandpresentsitscustomarycavity——theposteriorcornu——itcommonlyhappensthataparticularsulcusappearsupontheinnerandundersurfaceofthelobe，parallelwithandbeneaththefloorofthecornu——whichis，asitwere，archedovertheroofofthesulcus。Itisasifthegroovehadbeenformedbyindentingtheflooroftheposteriorhornfromwithoutwithabluntinstrument，sothatthefloorshouldriseasaconvexeminence。Nowthiseminenceiswhathasbeentermedthe’Hippocampusminor；’the’Hippocampusmajor’
　　beingalargereminenceinthefloorofthedescendingcornu。Whatmaybethefunctionalimportanceofeitherofthesestructuresweknownot。
　　Asiftodemonstrate，byastrikingexample，theimpossibilityoferectinganycerebralbarrierbetweenmanandtheapes，Naturehasprovidedus，inthelatteranimals，withanalmostcompleteseriesofgradationsfrombrainslittlehigherthanthatofaRodent，tobrainslittlelowerthanthatofMan。Anditisaremarkablecircumstancethatthough，sofarasourpresentknowledgeextends，there’is’onetruestructuralbreakintheseriesofformsofSimianbrains，thishiatusdoesnotliebetweenManandtheman-likeapes，butbetweenthelowerandthelowestSimians；or，inotherwords，betweentheoldandnewworldapesandmonkeys，andtheLemurs。EveryLemurwhichhasyetbeenexamined，infact，hasitscerebellumpartiallyvisiblefromabove，anditsposteriorlobe，withthecontainedposteriorcornuandhippocampusminor，moreorlessrudimentary。EveryMarmoset，Americanmonkey，old-worldmonkey，Baboon，orMan-likeape，onthecontrary，hasitscerebellumentirelyhidden，posteriorly，bythecerebrallobes，andpossessesalargeposteriorcornu，withawell-developedhippocampusminor。
　　FIG。20。——DrawingsoftheinternalcastsofaMan’sandofaChimpanzee’sskull，ofthesameabsolutelength，andplacedincorrespondingpositions。’A’。Cerebrum；’B’。Cerebellum。TheformerdrawingistakenfromacastintheMuseumoftheRoyalCollegeofSurgeons，thelatterfromthephotographofthecastofaChimpanzee’sskull，whichillustratesthepaperbyMr。Marshall’OntheBrainoftheChimpanzee’inthe’NaturalHistoryReview’forJuly，1861。ThesharperdefinitionoftheloweredgeofthecastofthecerebralchamberintheChimpanzeearisesfromthecircumstancethatthetentoriumremainedinthatskullandnotintheMan’s。ThecastmoreaccuratelyrepresentsthebraininChimpanzeethanintheMan；andthegreatbackwardprojectionoftheposteriorlobesofthecerebrumoftheformer，beyondthecerebellum，isconspicuous。
　　Inmanyofthesecreatures，suchastheSaimiri（’Chrysothrix’），thecerebrallobesoverlapandextendmuchfurtherbehindthecerebellum，inproportion，thantheydoinman（Fig。16）——anditisquitecertainthat，inall，thecerebellumiscompletelycoveredbehind，bywell-developedposteriorlobes。Thefactcanbeverifiedbyeveryonewhopossessestheskullofanyoldornewworldmonkey。For，inasmuchasthebraininallmammalscompletelyfillsthecranialcavity，itisobviousthatacastoftheinterioroftheskullwillreproducethegeneralformofthebrain，atanyratewithsuchminuteand，forthepresentpurpose，utterlyunimportantdifferencesasmayresultfromtheabsenceoftheenvelopingmembranesofthebraininthedryskull。Butifsuchacastbemadeinplaster，andcomparedwithasimilarcastoftheinteriorofahumanskull，itwillbeobviousthatthecastofthecerebralchamber，representingthecerebrumoftheape，ascompletelycoversoverandoverlapsthecastofthecerebellarchamber，representingthecerebellum，asitdoesintheman（Fig。20）。A
　　carelessobserver，forgettingthatasoftstructurelikethebrainlosesitspropershapethemomentitistakenoutoftheskull，mayindeedmistaketheuncoveredconditionofthecerebellumofanextractedanddistortedbrainforthenaturalrelationsoftheparts；buthiserrormustbecomepatenteventohimselfifhetrytoreplacethebrainwithinthecranialchamber。Tosupposethatthecerebellumofanapeisnaturallyuncoveredbehindisamiscomprehensioncomparableonlytothatofonewhoshouldimaginethataman’slungsalwaysoccupybutasmallportionofthethoraciccavity——becausetheydosowhenthechestisopened，andtheirelasticityisnolongerneutralizedbythepressureoftheair。
　　Andtheerroristhelessexcusable，asitmustbecomeapparenttoeveryonewhoexaminesasectionoftheskullofanyapeaboveaLemur，withouttakingthetroubletomakeacastofit。Forthereisaverymarkedgrooveineverysuchskull，asinthehumanskull——whichindicatesthelineofattachmentofwhatistermedthe’tentorium’——asortofparchment-likeshelf，orpartition，which，intherecentstate，isinterposedbetweenthecerebrumandcerebellum，andpreventstheformerfrompressinguponthelatter。（SeeFig。16。）
　　Thisgroove，therefore，indicatesthelineofseparationbetweenthatpartofthecranialcavitywhichcontainsthecerebrum，andthatwhichcontainsthecerebellum；andasthebrainexactlyfillsthecavityoftheskull，itisobviousthattherelationsofthesetwopartsofthecranialcavityatonceinformsusoftherelationsoftheircontents。
　　Nowinman，inalltheold-world，andinallthenew-worldSimiae，withoneexception，whenthefaceisdirectedforwards，thislineofattachmentofthetentorium，orimpressionforthelateralsinus，asitistechnicallycalled，isnearlyhorizontal，andthecerebralchamberinvariablyoverlapsorprojectsbehindthecerebellarchamber。IntheHowlerMonkeyor’Mycetes’（seeFig。16），thelinepassesobliquelyupwardsandbackwards，andthecerebraloverlapisalmostnil；whileintheLemurs，asinthelowermammals，thelineismuchmoreinclinedinthesamedirection，andthecerebellarchamberprojectsconsiderablybeyondthecerebral。
　　Whenthegravesterrorsrespectingpointssoeasilysettledasthisquestionrespectingtheposteriorlobescanbeauthoritativelypropounded，itisnowonderthatmattersofobservation，ofnoverycomplexcharacter，butstillrequiringacertainamountofcare，shouldhavefaredworse。Anyonewhocannotseetheposteriorlobeinanape’sbrainisnotlikelytogiveaveryvaluableopinionrespectingtheposteriorcornuorthehippocampusminor。Ifamancannotseeachurch，itispreposteroustotakehisopinionaboutitsaltar-pieceorpaintedwindow——sothatIdonotfeelboundtoenteruponanydiscussionofthesepoints，butcontentmyselfwithassuringthereaderthattheposteriorcornuandthehippocampusminor，havenowbeenseen——usually，atleastaswelldevelopedasinman，andoftenbetter——notonlyintheChimpanzee，theOrang，andtheGibbon，butinallthegeneraoftheoldworldbaboonsandmonkeys，andinmostofthenewworldforms，includingtheMarmosets。*
　　[Footnote]*Seethenoteattheendofthisessayforasuccincthistoryofthecontroversytowhichallusionisheremade。
　　FIG。21。——DrawingsofthecerebralhemispheresofaManandofaChimpanzeeofthesamelength，inordertoshowtherelativeproportionsoftheparts：theformertakenfromaspecimen，whichMr。
　　Flower，ConservatoroftheMuseumoftheRoyalCollegeofSurgeons，wasgoodenoughtodissectforme；thelatter，fromthephotographofasimilarlydissectedChimpanzee’sbrain，giveninMr。Marshall’spaperabovereferredto。’a’，posteriorlobe；’b’，lateralventricle；’c’，posteriorcornu；’x’，thehippocampusminor。
　　Infact，alltheabundantandtrustworthyevidence（consistingoftheresultsofcarefulinvestigationsdirectedtothedeterminationoftheseveryquestions，byskilledanatomists）whichwenowpossess，leadstotheconvictionthat，sofarfromtheposteriorlobe，theposteriorcornu，andthehippocampusminor，beingstructurespeculiartoandcharacteristicofman，astheyhavebeenoverandoveragainassertedtobe，evenafterthepublicationoftheclearestdemonstrationofthereverse，itispreciselythesestructureswhicharethemostmarkedcerebralcharacterscommontomanwiththeapes。TheyareamongthemostdistinctlySimianpeculiaritieswhichthehumanorganismexhibits。
　　Astotheconvolutions，thebrainsoftheapesexhibiteverystageofprogress，fromthealmostsmoothbrainoftheMarmoset，totheOrangandtheChimpanzee，whichfallbutlittlebelowMan。Anditismostremarkablethat，assoonasalltheprincipalsulciappear，thepatternaccordingtowhichtheyarearrangedisidenticalwiththatofthecorrespondingsulciofman。Thesurfaceofthebrainofamonkeyexhibitsasortofskeletonmapofman’s，andintheman-likeapesthedetailsbecomemoreandmorefilledin，untilitisonlyinminorcharacters，suchasthegreaterexcavationoftheanteriorlobes，theconstantpresenceoffissuresusuallyabsentinman，andthedifferentdispositionandproportionsofsomeconvolutions，thattheChimpanzee’sortheOrang’sbraincanbestructurallydistinguishedfromMan’s。
　　Sofarascerebralstructuregoes，therefore，itisclearthatMandifferslessfromtheChimpanzeeortheOrang，thanthesedoevenfromtheMonkeys，andthatthedifferencebetweenthebrainsoftheChimpanzeeandofManisalmostinsignificant，whencomparedwiththatbetweentheChimpanzeebrainandthatofaLemur。
　　Itmustnotbeoverlooked，however，thatthereisaverystrikingdifferenceinabsolutemassandweightbetweenthelowesthumanbrainandthatofthehighestape——adifferencewhichisallthemoreremarkablewhenwerecollectthatafullgrownGorillaisprobablyprettynearlytwiceasheavyasaBosjesman，orasmanyanEuropeanwoman。Itmaybedoubtedwhetherahealthyhumanadultbraineverweighedlessthanthirty-oneortwoounces，orthattheheaviestGorillabrainhasexceededtwentyounces。