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OFthepartsofanimalssomearesimple:towit，allsuchasdivideintopartsuniformwiththemselves，asfleshintoflesh；othersarecomposite，suchasdivideintopartsnotuniformwiththemselves，as，forinstance，thehanddoesnotdivideintohandsnorthefaceintofaces。
Andofsuchasthese，somearecallednotpartsmerely，butlimbsormembers。Sucharethosepartsthat，whileentireinthemselves，havewithinthemselvesotherdiverseparts:asforinstance，thehead，foot，hand，thearmasawhole，thechest；fortheseareallinthemselvesentireparts，andthereareotherdiversepartsbelongingtothem。
Allthosepartsthatdonotsubdivideintopartsuniformwiththemselvesarecomposedofpartsthatdososubdivide，forinstance，handiscomposedofflesh，sinews，andbones。Ofanimals，someresembleoneanotherinalltheirparts，whileothershavepartswhereintheydiffer。Sometimesthepartsareidenticalinformorspecies，as，forinstance，oneman'snoseoreyeresemblesanotherman'snoseoreye，fleshflesh，andbonebone；andinlikemannerwithahorse，andwithallotheranimalswhichwereckontobeofoneandthesamespecies:forasthewholeistothewhole，soeachtoeacharethepartsseverally。Inothercasesthepartsareidentical，saveonlyforadifferenceinthewayofexcessordefect，asisthecaseinsuchanimalsasareofoneandthesamegenus。By'genus'I
mean，forinstance，BirdorFish，foreachoftheseissubjecttodifferenceinrespectofitsgenus，andtherearemanyspeciesoffishesandofbirds。
Withinthelimitsofgenera，mostofthepartsasaruleexhibitdifferencesthroughcontrastofthepropertyoraccident，suchascolourandshape，towhichtheyaresubject:inthatsomearemoreandsomeinalessdegreethesubjectofthesamepropertyoraccident；andalsointhewayofmultitudeorfewness，magnitudeorparvitude，inshortinthewayofexcessordefect。Thusinsomethetextureofthefleshissoft，inothersfirm；somehavealongbill，othersashortone；somehaveabundanceoffeathers，othershaveonlyasmallquantity。Ithappensfurtherthatsomehavepartsthatothershavenot:forinstance，somehavespursandothersnot，somehavecrestsandothersnot；butasageneralrule，mostpartsandthosethatgotomakeupthebulkofthebodyareeitheridenticalwithoneanother，ordifferfromoneanotherinthewayofcontrastandofexcessanddefect。For'themore'and'theless'mayberepresentedas'excess'or'defect'。
Onceagain，wemayhavetodowithanimalswhosepartsareneitheridenticalinformnoryetidenticalsavefordifferencesinthewayofexcessordefect:buttheyarethesameonlyinthewayofanalogy，as，forinstance，boneisonlyanalogoustofish-bone，nailtohoof，handtoclaw，andscaletofeather；forwhatthefeatherisinabird，thescaleisinafish。
Theparts，then，whichanimalsseverallypossessarediversefrom，oridenticalwith，oneanotherinthefashionabovedescribed。
Andtheyaresofurthermoreinthewayoflocaldisposition:formanyanimalshaveidenticalorgansthatdifferinposition；forinstance，somehaveteatsinthebreast，othersclosetothethighs。
Ofthesubstancesthatarecomposedofpartsuniformorhomogeneouswiththemselves，somearesoftandmoist，othersaredryandsolid。Thesoftandmoistaresucheitherabsolutelyorsolongastheyareintheirnaturalconditions，as，forinstance，blood，serum，lard，suet，marrow，sperm，gall，milkinsuchashaveitfleshandthelike；andalso，inadifferentway，thesuperfluities，asphlegmandtheexcretionsofthebellyandthebladder。Thedryandsolidaresuchassinew，skin，vein，hair，bone，gristle，nail，hornatermwhichasappliedtothepartinvolvesanambiguity，sincethewholealsobyvirtueofitsformisdesignatedhorn，andsuchpartsaspresentananalogytothese。
Animalsdifferfromoneanotherintheirmodesofsubsistence，intheiractions，intheirhabits，andintheirparts。Concerningthesedifferencesweshallfirstspeakinbroadandgeneralterms，andsubsequentlyweshalltreatofthesamewithclosereferencetoeachparticulargenus。
Differencesaremanifestedinmodesofsubsistence，inhabits，inactionsperformed。Forinstance，someanimalsliveinwaterandothersonland。Andofthosethatliveinwatersomedosoinoneway，andsomeinanother:thatistosay，someliveandfeedinthewater，takeinandemitwater，andcannotliveifdeprivedofwater，asisthecasewiththegreatmajorityoffishes；othersgettheirfoodandspendtheirdaysinthewater，butdonottakeinwaterbutair，nordotheybringforthinthewater。Manyofthesecreaturesarefurnishedwithfeet，astheotter，thebeaver，andthecrocodile；somearefurnishedwithwings，asthediverandthegrebe；somearedestituteoffeet，asthewater-snake。Somecreaturesgettheirlivinginthewaterandcannotexistoutsideit:butforallthatdonottakeineitherairorwater，as，forinstance，thesea-nettleandtheoyster。Andofcreaturesthatliveinthewatersomeliveinthesea，someinrivers，someinlakes，andsomeinmarshes，asthefrogandthenewt。
Ofanimalsthatliveondrylandsometakeinairandemitit，whichphenomenaaretermed'inhalation'and'exhalation'；as，forinstance，manandallsuchlandanimalsasarefurnishedwithlungs。
Others，again，donotinhaleair，yetliveandfindtheirsustenanceondryland；as，forinstance，thewasp，thebee，andallotherinsects。Andby'insects'Imeansuchcreaturesashavenicksornotchesontheirbodies，eitherontheirbelliesoronbothbacksandbellies。
Andoflandanimalsmany，ashasbeensaid，derivetheirsubsistencefromthewater；butofcreaturesthatliveinandinhalewaternotasingleonederivesitssubsistencefromdryland。
Someanimalsatfirstliveinwater，andbyandbychangetheirshapeandliveoutofwater，asisthecasewithriverworms，foroutofthesethegadflydevelops。
Furthermore，someanimalsarestationary，andsomeareerratic。
Stationaryanimalsarefoundinwater，butnosuchcreatureisfoundondryland。Inthewateraremanycreaturesthatliveincloseadhesiontoanexternalobject，asisthecasewithseveralkindsofoyster。And，bytheway，thespongeappearstobeendowedwithacertainsensibility:asaproofofwhichitisallegedthatthedifficultyindetachingitfromitsmooringsisincreasedifthemovementtodetachitbenotcovertlyapplied。
Othercreaturesadhereatonetimetoanobjectanddetachthemselvesfromitatothertimes，asisthecasewithaspeciesoftheso-calledsea-nettle；forsomeofthesecreaturesseektheirfoodinthenight-timelooseandunattached。
Manycreaturesareunattachedbutmotionless，asisthecasewithoystersandtheso-calledholothuria。Somecanswim，as，forinstance，fishes，molluscs，andcrustaceans，suchasthecrawfish。Butsomeoftheselastmovebywalking，asthecrab，foritisthenatureofthecreature，thoughitlivesinwater，tomovebywalking。
Oflandanimalssomearefurnishedwithwings，suchasbirdsandbees，andthesearesofurnishedindifferentwaysonefromanother；othersarefurnishedwithfeet。Oftheanimalsthatarefurnishedwithfeetsomewalk，somecreep，andsomewriggle。Butnocreatureisableonlytomovebyflying，asthefishisableonlytoswim，fortheanimalswithleathernwingscanwalk；thebathasfeetandthesealhasimperfectfeet。
Somebirdshavefeetoflittlepower，andarethereforecalledApodes。Thislittlebirdispowerfulonthewing；and，asarule，birdsthatresembleitareweak-footedandstrongwinged，suchastheswallowandthedrepanisor？Alpineswift；forallthesebirdsresembleoneanotherintheirhabitsandintheirplumage，andmayeasilybemistakenoneforanother。Theapusistobeseenatallseasons，butthedrepanisonlyafterrainyweatherinsummer；forthisisthetimewhenitisseenandcaptured，though，asageneralrule，itisararebird。
Again，someanimalsmovebywalkingonthegroundaswellasbyswimminginwater。
Furthermore，thefollowingdifferencesaremanifestintheirmodesoflivingandintheiractions。Somearegregarious，somearesolitary，whethertheybefurnishedwithfeetorwingsorbefittedforalifeinthewater；andsomepartakeofbothcharacters，thesolitaryandthegregarious。Andofthegregarious，somearedisposedtocombineforsocialpurposes，otherstoliveeachforitsownself。
Gregariouscreaturesare，amongbirds，suchasthepigeon，thecrane，andtheswan；and，bytheway，nobirdfurnishedwithcrookedtalonsisgregarious。Ofcreaturesthatliveinwatermanykindsoffishesaregregarious，suchastheso-calledmigrants，thetunny，thepelamys，andthebonito。
Man，bytheway，presentsamixtureofthetwocharacters，thegregariousandthesolitary。
Socialcreaturesaresuchashavesomeonecommonobjectinview；
andthispropertyisnotcommontoallcreaturesthataregregarious。Suchsocialcreaturesareman，thebee，thewasp，theant，andthecrane。
Again，ofthesesocialcreaturessomesubmittoaruler，othersaresubjecttonogovernance:as，forinstance，thecraneandtheseveralsortsofbeesubmittoaruler，whereasantsandnumerousothercreaturesareeveryonehisownmaster。
Andagain，bothofgregariousandofsolitaryanimals，someareattachedtoafixedhomeandothersareerraticornomad。
Also，somearecarnivorous，somegraminivorous，someomnivorous:
whilstsomefeedonapeculiardiet，asforinstancethebeesandthespiders，forthebeelivesonhoneyandcertainothersweets，andthespiderlivesbycatchingflies；andsomecreaturesliveonfish。Again，somecreaturescatchtheirfood，otherstreasureitup；
whereasothersdonotso。
Somecreaturesprovidethemselveswithadwelling，othersgowithoutone:oftheformerkindarethemole，themouse，theant，thebee；ofthelatterkindaremanyinsectsandquadrupeds。
Further，inrespecttolocalityofdwellingplace，somecreaturesdwellunderground，asthelizardandthesnake；othersliveonthesurfaceoftheground，asthehorseandthedog。maketothemselvesholes，othersdonotSomearenocturnal，astheowlandthebat；othersliveinthedaylight。
Moreover，somecreaturesaretameandsomearewild:someareatalltimestame，asmanandthemule；othersareatalltimessavage，astheleopardandthewolf；andsomecreaturescanberapidlytamed，astheelephant。
Again，wemayregardanimalsinanotherlight。For，wheneveraraceofanimalsisfounddomesticated，thesameisalwaystobefoundinawildcondition；aswefindtobethecasewithhorses，kine，swine，men，sheep，goats，anddogs。
Further，someanimalsemitsoundwhileothersaremute，andsomeareendowedwithvoice:oftheselattersomehavearticulatespeech，whileothersareinarticulate；somearegiventocontinualchirpingandtwitteringsomearepronetosilence；somearemusical，andsomeunmusical；butallanimalswithoutexceptionexercisetheirpowerofsingingorchatteringchieflyinconnexionwiththeintercourseofthesexes。
Again，somecreaturesliveinthefields，asthecushat；someonthemountains，asthehoopoe；somefrequenttheabodesofmen，asthepigeon。
Some，again，arepeculiarlysalacious，asthepartridge，thebarn-doorcockandtheircongeners；othersareinclinedtochastity，asthewholetribeofcrows，forbirdsofthiskindindulgebutrarelyinsexualintercourse。
Ofmarineanimals，again，someliveintheopenseas，someneartheshore，someonrocks。
Furthermore，somearecombativeunderoffence；othersareprovidentfordefence。Oftheformerkindaresuchasactasaggressorsuponothersorretaliatewhensubjectedtoillusage，andofthelatterkindaresuchasmerelyhavesomemeansofguardingthemselvesagainstattack。
Animalsalsodifferfromoneanotherinregardtocharacterinthefollowingrespects。Somearegood-tempered，sluggish，andlittlepronetoferocity，astheox；othersarequicktempered，ferociousandunteachable，asthewildboar；someareintelligentandtimid，asthestagandthehare；othersaremeanandtreacherous，asthesnake；othersarenobleandcourageousandhigh-bred，asthelion；
othersarethorough-bredandwildandtreacherous，asthewolf:for，bytheway，ananimalishighbredifitcomefromanoblestock，andananimalisthorough-bredifitdoesnotdeflectfromitsracialcharacteristics。
Further，somearecraftyandmischievous，asthefox；somearespiritedandaffectionateandfawning，asthedog；othersareeasy-temperedandeasilydomesticated，astheelephant；othersarecautiousandwatchful，asthegoose；othersarejealousandself-conceited，asthepeacock。Butofallanimalsmanaloneiscapableofdeliberation。
Manyanimalshavememory，andarecapableofinstruction；butnoothercreatureexceptmancanrecallthepastatwill。
Withregardtotheseveralgeneraofanimals，particularsastotheirhabitsoflifeandmodesofexistencewillbediscussedmorefullybyandby。
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Commontoallanimalsaretheorganswherebytheytakefoodandtheorganswhereintotheytakeit；andtheseareeitheridenticalwithoneanother，orarediverseinthewaysabovespecified:towit，eitheridenticalinform，orvaryinginrespectofexcessordefect，orresemblingoneanotheranalogically，ordifferinginposition。
Furthermore，thegreatmajorityofanimalshaveotherorgansbesidestheseincommon，wherebytheydischargetheresiduumoftheirfood:Isay，thegreatmajority，forthisstatementdoesnotapplytoall。And，bytheway，theorganwherebyfoodistakeniniscalledthemouth，andtheorganwhereintoitistaken，thebelly；
theremainderofthealimentarysystemhasagreatvarietyofnames。
Nowtheresiduumoffoodistwofoldinkind，wetanddry，andsuchcreaturesashaveorgansreceptiveofwetresiduumareinvariablyfoundwithorgansreceptiveofdryresiduum；butsuchashaveorgansreceptiveofdryresiduumneednotpossessorgansreceptiveofwetresiduum。Inotherwords，ananimalhasabowelorintestineifithaveabladder；butananimalmayhaveabowelandbewithoutabladder。And，bytheway，Imayhereremarkthattheorganreceptiveofwetresiduumistermed'bladder'，andtheorganreceptiveofdryresiduum'intestineor'bowel'。
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Ofanimalsotherwise，agreatmanyhave，besidestheorgansabove-mentioned，anorganforexcretionofthesperm:andofanimalscapableofgenerationonesecretesintoanother，andtheotherintoitself。Thelatteristermed'female'，andtheformer'male'；butsomeanimalshaveneithermalenorfemale。Consequently，theorgansconnectedwiththisfunctiondifferinform，forsomeanimalshaveawombandothersanorgananalogousthereto。
Theabove-mentionedorgans，then，arethemostindispensablepartsofanimals；andwithsomeofthemallanimalswithoutexception，andwithothersanimalsforthemostpart，mustneedsbeprovided。
Onesense，andonealone，iscommontoallanimals-thesenseoftouch。Consequently，thereisnospecialnamefortheorganinwhichithasitsseat；forinsomegroupsofanimalstheorganisidentical，inothersitisonlyanalogous。
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Everyanimalissuppliedwithmoisture，and，iftheanimalbedeprivedofthesamebynaturalcausesorartificialmeans，deathensues:further，everyanimalhasanotherpartinwhichthemoistureiscontained。Thesepartsarebloodandvein，andinotheranimalsthereissomethingtocorrespond；butintheselatterthepartsareimperfect，beingmerelyfibreandserumorlymph。
Touchhasitsseatinapartuniformandhomogeneous，asinthefleshorsomethingofthekind，andgenerally，withanimalssuppliedwithblood，inthepartschargedwithblood。Inotheranimalsithasitsseatinpartsanalogoustothepartschargedwithblood；butinallcasesitisseatedinpartsthatintheirtexturearehomogeneous。
Theactivefaculties，onthecontrary，areseatedinthepartsthatareheterogeneous:as，forinstance，thebusinessofpreparingthefoodisseatedinthemouth，andtheofficeoflocomotioninthefeet，thewings，orinorganstocorrespond。
Again，someanimalsaresuppliedwithblood，asman，thehorse，andallsuchanimalsasare，whenfull-grown，eitherdestituteoffeet，ortwo-footed，orfour-footed；otheranimalsarebloodless，suchasthebeeandthewasp，and，ofmarineanimals，thecuttle-fish，thecrawfish，andallsuchanimalsashavemorethanfourfeet。
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Again，someanimalsareviviparous，othersoviparous，othersvermiparousor'grub-bearing'。Someareviviparous，suchasman，thehorse，theseal，andallotheranimalsthatarehair-coated，and，ofmarineanimals，thecetaceans，asthedolphin，andtheso-calledSelachia。Oftheselatteranimals，somehaveatubularair-passageandnogills，asthedolphinandthewhale:thedolphinwiththeair-passagegoingthroughitsback，thewhalewiththeair-passageinitsforehead；othershaveuncoveredgills，astheSelachia，thesharksandrays。
Whatwetermaneggisacertaincompletedresultofconceptionoutofwhichtheanimalthatistobedevelops，andinsuchawaythatinrespecttoitsprimitivegermitcomesfrompartonlyoftheegg，whiletherestservesforfoodasthegermdevelops。A'grub'ontheotherhandisathingoutofwhichinitsentiretytheanimalinitsentiretydevelops，bydifferentiationandgrowthoftheembryo。
Ofviviparousanimals，somehatcheggsintheirowninterior，ascreaturesofthesharkkind；othersengenderintheirinterioralivefoetus，asmanandthehorse。Whentheresultofconceptionisperfected，withsomeanimalsalivingcreatureisbroughtforth，withothersaneggisbroughttolight，withothersagrub。Oftheeggs，somehaveegg-shellsandareoftwodifferentcolourswithin，suchasbirds'eggs；othersaresoft-skinnedandofuniformcolour，astheeggsofanimalsofthesharkkind。Ofthegrubs，somearefromthefirstcapableofmovement，othersaremotionless。However，withregardtothesephenomenaweshallspeakpreciselyhereafterwhenwecometotreatofGeneration。
Furthermore，someanimalshavefeetandsomearedestitutethereof。Ofsuchashavefeetsomeanimalshavetwo，asisthecasewithmenandbirds，andwithmenandbirdsonly；somehavefour，asthelizardandthedog；somehavemore，asthecentipedeandthebee；butallsoeverthathavefeethaveanevennumberofthem。
Ofswimmingcreaturesthataredestituteoffeet，somehavewingletsorfins，asfishes:andofthesesomehavefourfins，twoaboveontheback，twobelowonthebelly，asthegiltheadandthebasse；somehavetwoonly，-towit，suchasareexceedinglylongandsmooth，astheeelandtheconger；somehavenoneatall，asthemuraena，butusetheseajustassnakesusedryground-andbytheway，snakesswiminwaterinjustthesameway。Oftheshark-kindsomehavenofins，suchasthosethatareflatandlong-tailed，astherayandthesting-ray，butthesefishesswimactuallybytheundulatorymotionoftheirflatbodies；thefishingfrog，however，hasfins，andsolikewisehaveallsuchfishesashavenottheirflatsurfacesthinnedofftoasharpedge。
Ofthoseswimmingcreaturesthatappeartohavefeet，asisthecasewiththemolluscs，thesecreaturesswimbytheaidoftheirfeetandtheirfinsaswell，andtheyswimmostrapidlybackwardsinthedirectionofthetrunk，asisthecasewiththecuttle-fishorsepiaandthecalamary；and，bytheway，neitheroftheselattercanwalkasthepoulpeoroctopuscan。
Thehard-skinnedorcrustaceousanimals，likethecrawfish，swimbytheinstrumentalityoftheirtail-parts；andtheyswimmostrapidlytailforemost，bytheaidofthefinsdevelopeduponthatmember。Thenewtswimsbymeansofitsfeetandtail；anditstailresemblesthatofthesheatfish，tocomparelittlewithgreat。
Ofanimalsthatcanflysomearefurnishedwithfeatheredwings，astheeagleandthehawk；somearefurnishedwithmembranouswings，asthebeeandthecockchafer；othersarefurnishedwithleathernwings，astheflyingfoxandthebat。Allflyingcreaturespossessedofbloodhavefeatheredwingsorleathernwings；thebloodlesscreatureshavemembranouswings，asinsects。Thecreaturesthathavefeatheredwingsorleathernwingshaveeithertwofeetornofeetatall:fortherearesaidtobecertainflyingserpentsinEthiopiathataredestituteoffeet。
Creaturesthathavefeatheredwingsareclassedasagenusunderthenameof'bird'；theothertwogenera，theleathern-wingedandmembrane-winged，areasyetwithoutagenerictitle。
Ofcreaturesthatcanflyandarebloodlesssomearecoleopterousorsheath-winged，fortheyhavetheirwingsinasheathorshard，likethecockchaferandthedung-beetle；othersaresheathless，andoftheselattersomearedipterousandsometetrapterous:tetrapterous，suchasarecomparativelylargeorhavetheirstingsinthetail，dipterous，suchasarecomparativelysmallorhavetheirstingsinfront。Thecoleopteraare，withoutexception，devoidofstings；thedipterahavethestinginfront，asthefly，thehorsefly，thegadfly，andthegnat。
Bloodlessanimalsasageneralruleareinferiorinpointofsizetobloodedanimals；though，bytheway，therearefoundintheseasomefewbloodlesscreaturesofabnormalsize，asinthecaseofcertainmolluscs。Andofthesebloodlessgenera，thosearethelargestthatdwellinmilderclimates，andthosethatinhabittheseaarelargerthanthoselivingondrylandorinfreshwater。
Allcreaturesthatarecapableofmotionmovewithfourormorepointsofmotion；thebloodedanimalswithfouronly:as，forinstance，manwithtwohandsandtwofeet，birdswithtwowingsandtwofeet，quadrupedsandfishesseverallywithfourfeetandfourfins。Creaturesthathavetwowingletsorfins，orthathavenoneatalllikeserpents，moveallthesamewithnotlessthanfourpointsofmotion；fortherearefourbendsintheirbodiesastheymove，ortwobendstogetherwiththeirfins。Bloodlessandmanyfootedanimals，whetherfurnishedwithwingsorfeet，movewithmorethanfourpointsofmotion；as，forinstance，thedayflymoveswithfourfeetandfourwings:and，Imayobserveinpassing，thiscreatureisexceptionalnotonlyinregardtothedurationofitsexistence，whenceitreceivesitsname，butalsobecausethoughaquadrupedithaswingsalso。
Allanimalsmovealike，four-footedandmany-footed；inotherwords，theyallmovecross-corner-wise。Andanimalsingeneralhavetwofeetinadvance；thecrabalonehasfour。
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Veryextensivegeneraofanimals，intowhichothersubdivisionsfall，arethefollowing:one，ofbirds；one，offishes；andanother，ofcetaceans。Nowallthesecreaturesareblooded。
Thereisanothergenusofthehard-shellkind，whichiscalledoyster；anotherofthesoft-shellkind，notasyetdesignatedbyasingleterm，suchasthespinycrawfishandthevariouskindsofcrabsandlobsters；andanotherofmolluscs，asthetwokindsofcalamaryandthecuttle-fish；thatofinsectsisdifferent。Alltheselattercreaturesarebloodless，andsuchofthemashavefeethaveagoodlynumberofthem；andoftheinsectssomehavewingsaswellasfeet。
Oftheotheranimalsthegeneraarenotextensive。Forinthemonespeciesdoesnotcomprehendmanyspecies；butinonecase，asman，thespeciesissimple，admittingofnodifferentiation，whileothercasesadmitofdifferentiation，buttheformslackparticulardesignations。
So，forinstance，creaturesthatarequdapedalandunprovidedwithwingsarebloodedwithoutexception，butsomeofthemareviviparous，andsomeoviparous。Suchasareviviparousarehair-coated，andsuchasareoviparousarecoveredwithakindoftessellatedhardsubstance；andthetessellatedbitsofthissubstanceare，asitwere，similarinregardtopositiontoascale。
Ananimalthatisbloodedandcapableofmovementondryland，butisnaturallyunprovidedwithfeet，belongstotheserpentgenus；
andanimalsofthisgenusarecoatedwiththetessellatedhornysubstance。Serpentsingeneralareoviparous；theadder，anexceptionalcase，isviviparous:fornotallviviparousanimalsarehair-coated，andsomefishesalsoareviviparous。
Allanimals，however，thatarehair-coatedareviviparous。For，bytheway，onemustregardasakindofhairsuchpricklyhairsashedgehogsandporcupinescarry；forthesespinesperformtheofficeofhair，andnotoffeetasisthecasewithsimilarpartsofsea-urchins。
Inthegenusthatcombinesallviviparousquadrupedsaremanyspecies，butundernocommonappellation。Theyareonlynamedasitwereonebyone，aswesayman，lion，stag，horse，dog，andsoon；
though，bytheway，thereisasortofgenusthatembracesallcreaturesthathavebushymanesandbushytails，suchasthehorse，theass，themule，thejennet，andtheanimalsthatarecalledHemioniinSyria，-fromtheirexternallyresemblingmules，thoughtheyarenotstrictlyofthesamespecies。Andthattheyarenotsoisprovedbythefactthattheymatewithandbreedfromoneanother。Forallthesereasons，wemusttakeanimalsspeciesbyspecies，anddiscusstheirpeculiaritiesseverally'
Theseprecedingstatements，then，havebeenputforwardthusinageneralway，asakindofforetasteofthenumberofsubjectsandofthepropertiesthatwehavetoconsiderinorderthatwemayfirstgetaclearnotionofdistinctivecharacterandcommonproperties。Byandbyweshalldiscussthesematterswithgreaterminuteness。
Afterthisweshallpassontothediscussionofcauses。Fortodothiswhentheinvestigationofthedetailsiscompleteistheproperandnaturalmethod，andthatwherebythesubjectsandthepremissesofourargumentwillafterwardsberenderedplain。
Inthefirstplacewemustlooktotheconstituentpartsofanimals。Foritisinawayrelativetotheseparts，firstandforemost，thatanimalsintheirentiretydifferfromoneanother:
eitherinthefactthatsomehavethisorthat，whiletheyhavenotthatorthis；orbypeculiaritiesofpositionorofarrangement；orbythedifferencesthathavebeenpreviouslymentioned，dependingupondiversityofform，orexcessordefectinthisorthatparticular，onanalogy，oroncontrastsoftheaccidentalqualities。
Tobeginwith，wemusttakeintoconsiderationthepartsofMan。For，justaseachnationiswonttoreckonbythatmonetarystandardwithwhichitismostfamiliar，somustwedoinothermatters。And，ofcourse，manistheanimalwithwhichweareallofusthemostfamiliar。
Nowthepartsareobviousenoughtophysicalperception。However，withtheviewofobservingdueorderandsequenceandofcombiningrationalnotionswithphysicalperception，weshallproceedtoenumeratetheparts:firstly，theorganic，andafterwardsthesimpleornon-composite。
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Thechiefpartsintowhichthebodyasawholeissubdivided，arethehead，theneck，thetrunkextendingfromthenecktotheprivyparts，whichiscalledthethorax，twoarmsandtwolegs。
Ofthepartsofwhichtheheadiscomposedthehair-coveredportioniscalledthe'skull'。Thefrontportionofitistermed'bregma'or'sinciput'，developedafterbirth-foritisthelastofallthebonesinthebodytoacquiresolidity，-thehinderpartistermedthe'occiput'，andthepartinterveningbetweenthesinciputandtheocciputisthe'crown'。Thebrainliesunderneaththesinciput；theocciputishollow。Theskullconsistsentirelyofthinbone，roundedinshape，andcontainedwithinawrapperoffleshlessskin。
Theskullhassutures:one，ofcircularform，inthecaseofwomen；inthecaseofmen，asageneralrule，threemeetingatapoint。Instanceshavebeenknownofaman'sskulldevoidofsuturealtogether。Intheskullthemiddleline，wherethehairparts，iscalledthecrownorvertex。Insomecasesthepartingisdouble；
thatistosay，somemenaredoublecrowned，notinregardtothebonyskull，butinconsequenceofthedoublefallorsetofthehair。
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Thepartthatliesundertheskulliscalledthe'face':butinthecaseofmanonly，forthetermisnotappliedtoafishortoanox。Inthefacethepartbelowthesinciputandbetweentheeyesistermedtheforehead。Whenmenhavelargeforeheads，theyareslowtomove；whentheyhavesmallones，theyarefickle；whentheyhavebroadones，theyareapttobedistraught；whentheyhaveforeheadsroundedorbulgingout，theyarequick-tempered。
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Underneaththeforeheadaretwoeyebrows。Straighteyebrowsareasignofsoftnessofdisposition；suchascurveintowardsthenose，ofharshness；suchascurveouttowardsthetemples，ofhumouranddissimulation；suchasaredrawnintowardsoneanother，ofjealousy。
Undertheeyebrowscometheeyes。Thesearenaturallytwoinnumber。Eachofthemhasanupperandalowereyelid，andthehairsontheedgesofthesearetermed'eyelashes'。Thecentralpartoftheeyeincludesthemoistpartwherebyvisioniseffected，termedthe'pupil'，andthepartsurroundingitcalledthe'black'；thepartoutsidethisisthe'white'。Apartcommontotheupperandlowereyelidisapairofnicksorcorners，oneinthedirectionofthenose，andtheotherinthedirectionofthetemples。Whenthesearelongtheyareasignofbaddisposition；ifthesidetowardthenostrilbefleshyandcomb-like，theyareasignofdishonesty。
Allanimals，asageneralrule，areprovidedwitheyes，exceptingtheostracodermsandotherimperfectcreatures；atallevents，allviviparousanimalshaveeyes，withtheexceptionofthemole。Andyetonemightassertthat，thoughthemolehasnoteyesinthefullsense，yetithaseyesinakindofaway。Forinpointofabsolutefactitcannotsee，andhasnoeyesvisibleexternally；butwhentheouterskinisremoved，itisfoundtohavetheplacewhereeyesareusuallysituated，andtheblackpartsoftheeyesrightlysituated，andalltheplacethatisusuallydevotedontheoutsidetoeyes:
showingthatthepartsarestuntedindevelopment，andtheskinallowedtogrowover。
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Oftheeyethewhiteisprettymuchthesameinallcreatures；butwhatiscalledtheblackdiffersinvariousanimals。Somehavetherimblack，somedistinctlyblue，somegreyish-blue，somegreenish；andthislastcolouristhesignofanexcellentdisposition，andisparticularlywelladaptedforsharpnessofvision。Manistheonly，ornearlytheonly，creature，thathaseyesofdiversecolours。
Animals，asarule，haveeyesofonecolouronly。Somehorseshaveblueeyes。
Ofeyes，somearelarge，somesmall，somemedium-sized；ofthese，themedium-sizedarethebest。Moreover，eyessometimesprotrude，sometimesrecede，sometimesareneitherprotrudingnorreceding。Ofthese，therecedingeyeisinallanimalsthemostacute；butthelastkindarethesignofthebestdisposition。Again，eyesaresometimesinclinedtowinkunderobservation，sometimestoremainopenandstaring，andsometimesaredisposedneithertowinknorstare。Thelastkindarethesignofthebestnature，andoftheothers，thelatterkindindicatesimpudence，andtheformerindecision。
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Furthermore，thereisaportionofthehead，wherebyananimalhears，apartincapableofbreathing，the'ear'。Isay'incapableofbreathing'，forAlcmaeonismistakenwhenhesaysthatgoatsinspirethroughtheirears。Oftheearonepartisunnamed，theotherpartiscalledthe'lobe'；anditisentirelycomposedofgristleandflesh。Theearisconstructedinternallylikethetrumpet-shell，andtheinnermostboneisliketheearitself，andintoitattheendthesoundmakesitsway，asintothebottomofajar。Thisreceptacledoesnotcommunicatebyanypassagewiththebrain，butdoessowiththepalate，andaveinextendsfromthebraintowardsit。
Theeyesalsoareconnectedwiththebrain，andeachofthemliesattheendofalittlevein。Ofanimalspossessedofearsmanistheonlyonethatcannotmovethisorgan。Ofcreaturespossessedofhearing，somehaveears，whilstothershavenone，butmerelyhavethepassagesforearsvisible，as，forexample，featheredanimalsoranimalscoatedwithhornytessellates。
Viviparousanimals，withtheexceptionoftheseal，thedolphin，andthoseotherswhichafterasimilarfashiontothesearecetaceans，areallprovidedwithears；for，bytheway，theshark-kindarealsoviviparous。Now，thesealhasthepassagesvisiblewherebyithears；
butthedolphincanhear，buthasnoears，noryetanypassagesvisible。Butmanaloneisunabletomovehisears，andallotheranimalscanmovethem。Andtheearslie，withman，inthesamehorizontalplanewiththeeyes，andnotinaplaneabovethemasisthecasewithsomequadrupeds。Ofears，somearefine，somearecoarse，andsomeareofmediumtexture；thelastkindarebestforhearing，buttheyserveinnowaytoindicatecharacter。Someearsarelarge，somesmall，somemedium-sized；again，somestandoutfar，somelieincloseandtight，andsometakeupamediumposition；ofthesesuchasareofmediumsizeandofmediumpositionareindicationsofthebestdisposition，whilethelargeandoutstandingonesindicateatendencytoirrelevanttalkorchattering。Thepartinterceptedbetweentheeye，theear，andthecrownistermedthe'temple'。Again，thereisapartofthecountenancethatservesasapassageforthebreath，the'nose'。Foramaninhalesandexhalesbythisorgan，andsneezingiseffectedbyitsmeans:whichlastisanoutwardrushofcollectedbreath，andistheonlymodeofbreathusedasanomenandregardedassupernatural。Bothinhalationandexhalationgorightonfromthenosetowardsthechest；andwiththenostrilsaloneandseparatelyitisimpossibletoinhaleorexhale，owingtothefactthattheinspirationandrespirationtakeplacefromthechestalongthewindpipe，andnotbyanyportionconnectedwiththehead；andindeeditispossibleforacreaturetolivewithoutusingthisprocessofnasalrespiration。
Again，smellingtakesplacebymeansofthenose，-smelling，orthesensiblediscriminationofodour。Andthenostriladmitsofeasymotion，andisnot，liketheear，intrinsicallyimmovable。Apartofit，composedofgristle，constitutes，aseptumorpartition，andpartisanopenpassage；forthenostrilconsistsoftwoseparatechannels。Thenostrilornoseoftheelephantislongandstrong，andtheanimalusesitlikeahand；forbymeansofthisorganitdrawsobjectstowardsit，andtakesholdofthem，andintroducesitsfoodintoitsmouth，whetherliquidordryfood，anditistheonlylivingcreaturethatdoesso。
Furthermore，therearetwojaws；thefrontpartofthemconstitutesthechin，andthehinderpartthecheek。Allanimalsmovethelowerjaw，withtheexceptionoftherivercrocodile；thiscreaturemovestheupperjawonly。
Nextafterthenosecometwolips，composedofflesh，andfacileofmotion。Themouthliesinsidethejawsandlips。Partsofthemoutharetherooforpalateandthepharynx。
Thepartthatissensibleoftasteisthetongue。Thesensationhasitsseatatthetipofthetongue；iftheobjecttobetastedbeplacedontheflatsurfaceoftheorgan，thetasteislesssensiblyexperienced。Thetongueissensitiveinallotherwayswhereinfleshingeneralisso:thatis，itcanappreciatehardness，orwarmthandcold，inanypartofit，justasitcanappreciatetaste。Thetongueissometimesbroad，sometimesnarrow，andsometimesofmediumwidth；
thelastkindisthebestandtheclearestinitsdiscriminationoftaste。Moreover，thetongueissometimeslooselyhung，andsometimesfastened:asinthecaseofthosewhomumbleandwholisp。
Thetongueconsistsofflesh，softandspongy，andtheso-called'epiglottis'isapartofthisorgan。
Thatpartofthemouththatsplitsintotwobitsiscalledthe'tonsils'；thatpartthatsplitsintomanybits，the'gums'。Boththetonsilsandthegumsarecomposedofflesh。Inthegumsareteeth，composedofbone。
Insidethemouthisanotherpart，shapedlikeabunchofgrapes，apillarstreakedwithveins。Ifthispillargetsrelaxedandinflameditiscalled'uvula'or'bunchofgrapes'，anditthenhasatendencytobringaboutsuffocation。
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Theneckisthepartbetweenthefaceandthetrunk。OfthisthefrontpartisthelarynxlandthebackparttheurThefrontpart，composedofgristle，throughwhichrespirationandspeechiseffected，istermedthe'windpipe'；thepartthatisfleshyistheoesophagus，insidejustinfrontofthechine。Theparttothebackoftheneckistheepomis，or'shoulder-point'。
Thesethenarethepartstobemetwithbeforeyoucometothethorax。
Tothetrunkthereisafrontpartandabackpart。Nextaftertheneckinthefrontpartisthechest，withapairofbreasts。Toeachofthebreastsisattachedateatornipple，throughwhichinthecaseoffemalesthemilkpercolates；andthebreastisofaspongytexture。Milk，bytheway，isfoundattimesinthemale；butwiththemalethefleshofthebreastistough，withthefemaleitissoftandporous。
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Nextafterthethoraxandinfrontcomesthe'belly'，anditsrootthe'navel'。Underneaththisrootthebilateralpartisthe'flank':
theundividedpartbelowthenavel，the'abdomen'，theextremityofwhichistheregionofthe'pubes'；abovethenavelthe'hypochondrium'；thecavitycommontothehypochondriumandtheflankisthegut-cavity。
Servingasabracegirdletothehinderpartsisthepelvis，andhenceitgetsitsnameosphus，foritissymmetricalisophuesinappearance；ofthefundamentthepartforrestingonistermedthe'rump'，andthepartwhereonthethighpivotsistermedthe'socket'oracetabulum。
The'womb'isapartpeculiartothefemale；andthe'penis'ispeculiartothemale。Thislatterorganisexternalandsituatedattheextremityofthetrunk；itiscomposedoftwoseparateparts:ofwhichtheextremepartisfleshy，doesnotalterinsize，andiscalledtheglans；androundaboutitisaskindevoidofanyspecifictitle，whichintegumentifitbecutasundernevergrowstogetheragain，anymorethandoesthejawortheeyelid。Andtheconnexionbetweenthelatterandtheglansiscalledthefrenum。Theremainingpartofthepenisiscomposedofgristle；itiseasilysusceptibleofenlargement；anditprotrudesandrecedesinthereversedirectionstowhatisobservableintheidenticalorganincats。Underneaththepenisaretwo'testicles'，andtheintegumentoftheseisaskinthatistermedthe'scrotum'。
Testiclesarenotidenticalwithflesh，andarenotaltogetherdiversefromit。Butbyandbyweshalltreatinanexhaustivewayregardingallsuchparts。
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Theprivypartofthefemaleisincharacteroppositetothatofthemale。Inotherwords，thepartunderthepubesisholloworreceding，andnot，likethemaleorgan，protruding。Further，thereisan'urethra'outsidethewomb；whichorganservesasapassageforthespermofthemale，andasanoutletforliquidexcretiontobothsexes。
Thepartcommontotheneckandchestisthe'throat'；the'armpit'iscommontoside，arm，andshoulder；andthe'groin'iscommontothighandabdomen。Thepartinsidethethighandbuttocksisthe'perineum'，andthepartoutsidethethighandbuttocksisthe'hypoglutis'。
Thefrontpartsofthetrunkhavenowbeenenumerated。
Thepartbehindthechestistermedthe'back'。
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Partsofthebackareapairof'shoulderblades'，the'back-bone'，and，underneathonalevelwiththebellyinthetrunk，the'loins'。Commontotheupperandlowerpartofthetrunkarethe'ribs'，eightoneitherside，forastotheso-calledseven-ribbedLigyanswehavenotreceivedanytrustworthyevidence。
Man，then，hasanupperandalowerpart，afrontandabackpart，arightandaleftside。Nowtherightandtheleftsideareprettywellalikeintheirpartsandidenticalthroughout，exceptthattheleftsideistheweakerofthetwo；butthebackpartsdonotresemblethefrontones，neitherdotheloweronestheupper:onlythattheseupperandlowerpartsmaybesaidtoresembleoneanotherthusfar，that，ifthefacebeplumpormeagre，theabdomenisplumpormeagretocorrespond；andthatthelegscorrespondtothearms，andwheretheupperarmisshortthethighisusuallyshortalso，andwherethefeetaresmallthehandsaresmallcorrespondingly。
Ofthelimbs，oneset，formingapair，is'arms'。Tothearmbelongthe'shoulder'，'upper-arm'，'elbow'，'fore-arm'，and'hand'。
Tothehandbelongthe'palm'，andthefive'fingers'。Thepartofthefingerthatbendsistermed'knuckle'，thepartthatisinflexibleistermedthe'phalanx'。Thebigfingerorthumbissingle-jointed，theotherfingersaredoublejointed。Thebendingbothofthearmandofthefingertakesplacefromwithoutinwardsinallcases；andthearmbendsattheelbow。Theinnerpartofthehandistermedthepalm'，andisfleshyanddividedbyjointsorlines:inthecaseoflong-livedpeoplebyoneortwoextendingrightacross，inthecaseoftheshort-livedbytwo，notsoextending。Thejointbetweenhandandarmistermedthe'wrist'。Theoutsideorbackofthehandissinewy，andhasnospecificdesignation。
Thereisanotherduplicatelimb，the'leg'。Ofthislimbthedouble-knobbedpartistermedthe'thigh-bone'，theslidingpartofthe'kneecap'，thedouble-bonedpartthe'leg'；thefrontpartofthislatteristermedthe'shin'，andthepartbehinditthe'calf'，whereinthefleshissinewyandvenous，insomecasesdrawnupwardstowardsthehollowbehindtheknee，asinthecaseofpeoplewithlargehips，andinothercasesdrawndownwards。Thelowerextremityoftheshinisthe'ankle'，duplicateineitherleg。Thepartofthelimbthatcontainsamultiplicityofbonesisthe'foot'。Thehinderpartofthefootisthe'heel'；atthefrontofitthedividedpartconsistsof'toes'，fiveinnumber；thefleshypartunderneathisthe'ball'；theupperpartorbackofthefootissinewyandhasnoparticularappellation；ofthetoe，oneportionisthe'nail'andanotherthe'joint'，andthenailisinallcasesattheextremity；
andtoesarewithoutexceptionsinglejointed。Menthathavetheinsideorsoleofthefootclumsyandnotarched，thatis，thatwalkrestingontheentireunder-surfaceoftheirfeet，arepronetoroguery。Thejointcommontothighandshinisthe'knee'。
These，then，arethepartscommontothemaleandthefemalesex。
Therelativepositionofthepartsastoupanddown，ortofrontandback，ortorightandleft，allthisasregardsexternalsmightsafelybelefttomereordinaryperception。Butforallthat，wemusttreatofthemforthesamereasonastheonepreviouslybroughtforward；thatistosay，wemustrefertotheminorderthatadueandregularsequencemaybeobservedinourexposition，andinorderthatbytheenumerationoftheseobviousfactsdueattentionmaybesubsequentlygiventothosepartsinmenandotheranimalsthatarediverseinanywayfromoneanother。
Inman，aboveallotheranimals，theterms'upper'and'lower'
areusedinharmonywiththeirnaturalpositions；forinhim，upperandlowerhavethesamemeaningaswhentheyareappliedtotheuniverseasawhole。Inlikemannertheterms，'infront'，'behind'，'right'and'left'，areusedinaccordancewiththeirnaturalsense。
Butinregardtootheranimals，insomecasesthesedistinctionsdonotexist，andinotherstheydoso，butinavagueway。Forinstance，theheadwithallanimalsisupandaboveinrespecttotheirbodies；butmanalone，ashasbeensaid，has，inmaturity，thispartuppermostinrespecttothematerialuniverse。
Nextaftertheheadcomestheneck，andthenthechestandtheback:theoneinfrontandtheotherbehind。Nextafterthesecomethebelly，theloins，thesexualparts，andthehaunches；thenthethighandshin；and，lastly，thefeet。
Thelegsbendfrontwards，inthedirectionofactualprogression，andfrontwardsalsoliesthatpartofthefootwhichisthemosteffectiveofmotion，andtheflexureofthatpart；buttheheelliesattheback，andtheankleboneslielaterally，earwise。Thearmsaresituatedtorightandleft，andbendinwards:sothattheconvexitiesformedbybentarmsandlegsarepracticallyfacetofacewithoneanotherinthecaseofman。
Asforthesensesandfortheorgansofsensation，theeyes，thenostrils，andthetongue，allalikearesituatedfrontwards；thesenseofhearing，andtheorganofhearing，theear，issituatedsideways，onthesamehorizontalplanewiththeeyes。Theeyesinmanare，inproportiontohissize，nearertooneanotherthaninanyotheranimal。
Ofthesensesmanhasthesenseoftouchmorerefinedthananyanimal，andsoalso，butinlessdegree，thesenseoftaste；inthedevelopmentoftheothersensesheissurpassedbyagreatnumberofanimals。
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Theparts，then，thatareexternallyvisiblearearrangedinthewayabovestated，andasarulehavetheirspecialdesignations，andfromuseandwontareknownfamiliarlytoall；butthisisnotthecasewiththeinnerparts。Forthefactisthattheinnerpartsofmanaretoaverygreatextentunknown，andtheconsequenceisthatwemusthaverecoursetoanexaminationoftheinnerpartsofotheranimalswhosenatureinanywayresemblesthatofman。
Inthefirstplacethen，thebrainliesinthefrontpartofthehead。Andthisholdsalikewithallanimalspossessedofabrain；
andallbloodedanimalsarepossessedthereof，and，bytheway，molluscsaswell。But，takingsizeforsizeofanimal，thelargestbrain，andthemoistest，isthatofman。Twomembranesencloseit:thestrongeroneneartheboneoftheskull；theinnerone，roundthebrainitself，isfiner。Thebraininallcasesisbilateral。Behindthis，rightattheback，comeswhatistermedthe'cerebellum'，differinginformfromthebrainaswemaybothfeelandsee。
Thebackoftheheadiswithallanimalsemptyandhollow，whateverbeitssizeinthedifferentanimals。Forsomecreatureshavebigheadswhilethefacebelowissmallinproportion，asisthecasewithround-facedanimals；somehavelittleheadsandlongjaws，asisthecase，withoutexception，amonganimalsofthemane-and-tailspecies。
Thebraininallanimalsisbloodless，devoidofveins，andnaturallycoldtothetouch；inthegreatmajorityofanimalsithasasmallhollowinitscentre。Thebrain-caularounditisreticulatedwithveins；andthisbrain-caulisthatskin-likemembranewhichcloselysurroundsthebrain。Abovethebrainisthethinnestandweakestboneofthehead，whichistermedor'sinciput'。
Fromtheeyetheregothreeductstothebrain:thelargestandthemedium-sizedtothecerebellum，theleasttothebrainitself；andtheleastistheonesituatednearesttothenostril。Thetwolargestones，then，runsidebysideanddonotmeet；themedium-sizedonesmeet-andthisisparticularlyvisibleinfishes，-fortheylienearerthanthelargeonestothebrain；thesmallestpairarethemostwidelyseparatefromoneanother，anddonotmeet。
Insidetheneckiswhatistermedtheoesophaguswhoseothernameisderivedoesophagusfromitslengthandnarrowness，andthewindpipe。Thewindpipeissituatedinfrontoftheoesophagusinallanimalsthathaveawindpipe，andallanimalshaveonethatarefurnishedwithlungs。Thewindpipeismadeupofgristle，issparinglysuppliedwithblood，andisstreakedallroundwithnumerousminuteveins；itissituated，initsupperpart，nearthemouth，belowtheapertureformedbythenostrilsintothemouth-anaperturethroughwhich，whenmen，indrinking，inhaleanyoftheliquid，thisliquidfindsitswayoutthroughthenostrils。Inbetwixtthetwoopeningscomestheso-calledepiglottis，anorgancapableofbeingdrawnoverandcoveringtheorificeofthewindpipecommunicatingwiththemouth；
theendofthetongueisattachedtotheepiglottis。Intheotherdirectionthewindpipeextendstotheintervalbetweenthelungs，andhereuponbifurcatesintoeachofthetwodivisionsofthelung；
forthelunginallanimalspossessedoftheorganhasatendencytobedouble。Inviviparousanimals，however，theduplicationisnotsoplainlydiscernibleasinotherspecies，andtheduplicationisleastdiscernibleinman。Andinmantheorganisnotsplitintomanyparts，asisthecasewithsomevivipara，neitherisitsmooth，butitssurfaceisuneven。
Inthecaseoftheovipara，suchasbirdsandoviparousquadrupeds，thetwopartsoftheorganareseparatedtoadistancefromoneanother，sothatthecreaturesappeartobefurnishedwithapairoflungs；andfromthewindpipe，itselfsingle，therebranchofftwoseparatepartsextendingtoeachofthetwodivisionsofthelung。Itisattachedalsotothegreatveinandtowhatisdesignatedthe'aorta'。Whenthewindpipeischargedwithair，theairpassesontothehollowpartsofthelung。Thesepartshavedivisions，composedofgristle，whichmeetatanacuteangle；fromthedivisionsrunpassagesthroughtheentirelung，givingoffsmallerandsmallerramifications。Theheartalsoisattachedtothewindpipe，byconnexionsoffat，gristle，andsinew；andatthepointofjuncturethereisahollow。Whenthewindpipeischargedwithair，theentranceoftheairintotheheart，thoughimperceptibleinsomeanimals，isperceptibleenoughinthelargerones。Sucharethepropertiesofthewindpipe，andittakesinandthrowsoutaironly，andtakesinnothingelseeitherdryorliquid，orelseitcausesyoupainuntilyoushallhavecoughedupwhatevermayhavegonedown。
Theoesophaguscommunicatesatthetopwiththemouth，closetothewindpipe，andisattachedtothebackboneandthewindpipebymembranousligaments，andatlastfindsitswaythroughthemidriffintothebelly。Itiscomposedofflesh-likesubstance，andiselasticbothlengthwaysandbreadthways。
Thestomachofmanresemblesthatofadog；foritisnotmuchbiggerthanthebowel，butissomewhatlikeabowelofmorethanusualwidth；thencomesthebowel，single，convoluted，moderatelywide。
Thelowerpartofthegutislikethatofapig；foritisbroad，andthepartfromittothebuttocksisthickandshort。Thecaul，orgreatomentum，isattachedtothemiddleofthestomach，andconsistsofafattymembrane，asisthecasewithallotheranimalswhosestomachsaresingleandwhichhaveteethinbothjaws。
Themesenteryisoverthebowels；thisalsoismembranousandbroad，andturnstofat。Itisattachedtothegreatveinandtheaorta，andthererunthroughitanumberofveinscloselypackedtogether，extendingtowardstheregionofthebowels，beginningaboveandendingbelow。
Somuchforthepropertiesoftheoesophagus，thewindpipe，andthestomach。
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Thehearthasthreecavities，andissituatedabovethelungatthedivisionofthewindpipe，andisprovidedwithafattyandthickmembranewhereitfastensontothegreatveinandtheaorta。Itlieswithitstaperingportionupontheaorta，andthisportionissimilarlysituatedinrelationtothechestinallanimalsthathaveachest。Inallanimalsalike，inthosethathaveachestandinthosethathavenone，theapexoftheheartpointsforwards，althoughthisfactmightpossiblyescapenoticebyachangeofpositionunderdissection。Theroundedendoftheheartisatthetop。Theapexistoagreatextentfleshyandcloseintexture，andinthecavitiesoftheheartaresinews。Asaruletheheartissituatedinthemiddleofthechestinanimalsthathaveachest，andinmanitissituatedalittletotheleft-handside，leaningalittlewayfromthedivisionofthebreaststowardstheleftbreastintheupperpartofthechest。
Theheartisnotlarge，andinitsgeneralshapeitisnotelongated；infact，itissomewhatroundinform:only，beitremembered，itissharp-pointedatthebottom。Ithasthreecavities，ashasbeensaid:theright-handonethelargestofthethree，theleft-handonetheleast，andthemiddleoneintermediateinsize。Allthesecavities，eventhetwosmallones，areconnectedbypassageswiththelung，andthisfactisrenderedquiteplaininoneofthecavities。Andbelow，atthepointofattachment，inthelargestcavitythereisaconnexionwiththegreatveinnearwhichthemesenterylies；andinthemiddleonethereisaconnexionwiththeaorta。
Canalsleadfromtheheartintothelung，andbranchoffjustasthewindpipedoes，runningalloverthelungparallelwiththepassagesfromthewindpipe。Thecanalsfromtheheartareuppermost；
andthereisnocommonpassage，butthepassagesthroughtheirhavingacommonwallreceivethebreathandpassitontotheheart；
andoneofthepassagesconveysittotherightcavity，andtheothertotheleft。
Withregardtothegreatveinandtheaortaweshall，byandby，treatofthemtogetherinadiscussiondevotedtothemandtothemalone。Inallanimalsthatarefurnishedwithalung，andthatarebothinternallyandexternallyviviparous，thelungisofallorgansthemostrichlysuppliedwithblood；forthelungisthroughoutspongyintexture，andalongbyeverysingleporeinitgobranchesfromthegreatvein。Thosewhoimagineittobeemptyarealtogethermistaken；andtheyareledintotheirerrorbytheirobservationoflungsremovedfromanimalsunderdissection，outofwhichorgansthebloodhadallescapedimmediatelyafterdeath。
Oftheotherinternalorganstheheartalonecontainsblood。
Andthelunghasbloodnotinitselfbutinitsveins，butthehearthasbloodinitself；forineachofitsthreecavitiesithasblood，butthethinnestbloodiswhatithasinitscentralcavity。
Underthelungcomesthethoracicdiaphragmormidriff，attachedtotheribs，thehypochondriaandthebackbone，withathinmembraneinthemiddleofit。Ithasveinsrunningthroughit；andthediaphragminthecaseofmanisthickerinproportiontothesizeofhisframethaninotheranimals。
Underthediaphragmontheright-handsideliesthe'liver'，andontheleft-handsidethe'spleen'，alikeinallanimalsthatareprovidedwiththeseorgansinanordinaryandnotpreternaturalway；for，beitobserved，insomequadrupedstheseorganshavebeenfoundinatransposedposition。Theseorgansareconnectedwiththestomachbythecaul。
Tooutwardviewthespleenofmanisnarrowandlong，resemblingtheself-sameorganinthepig。Theliverinthegreatmajorityofanimalsisnotprovidedwitha'gall-bladder'；butthelatterispresentinsome。Theliverofamanisround-shaped，andresemblesthesameorganintheox。And，bytheway，theabsenceabovereferredtoofagall-bladderisattimesmetwithinthepracticeofaugury。Forinstance，inacertaindistrictoftheChalcidicsettlementinEuboeathesheeparedevoidofgall-bladders；andinNaxosnearlyallthequadrupedshaveonesolargethatforeignerswhentheyoffersacrificewithsuchvictimsarebewilderedwithfright，undertheimpressionthatthephenomenonisnotduetonaturalcauses，butbodessomemischieftotheindividualofferersofthesacrifice。
Again，theliverisattachedtothegreatvein，butithasnocommunicationwiththeaorta；fortheveinthatgoesofffromthegreatveingoesrightthroughtheliver，atapointwherearetheso-called'portals'oftheliver。Thespleenalsoisconnectedonlywiththegreatvein，foraveinextendstothespleenofffromit。
Aftertheseorganscomethe'kidneys'，andtheseareplacedclosetothebackbone，andresembleincharacterthesameorganinkine。
Inallanimalsthatareprovidedwiththisorgan，therightkidneyissituatedhigherupthantheother。Ithasalsolessfattysubstancethantheleft-handoneandislessmoist。Andthisphenomenonalsoisobservableinalltheotheranimalsalike。
Furthermore，passagesorductsleadintothekidneysbothfromthegreatveinandfromtheaorta，onlynotintothecavity。For，bytheway，thereisacavityinthemiddleofthekidney，biggerinsomecreaturesandlessinothers；butthereisnoneinthecaseoftheseal。Thislatteranimalhaskidneysresemblinginshapetheidenticalorganinkine，butinitscasetheorgansaremoresolidthaninanyotherknowncreature。Theductsthatleadintothekidneyslosethemselvesinthesubstanceofthekidneysthemselves；andtheproofthattheyextendnofartherrestsonthefactthattheycontainnoblood，norisanyclotfoundtherein。Thekidneys，however，have，ashasbeensaid，asmallcavity。Fromthiscavityinthekidneythereleadtwoconsiderableductsoruretersintothebladder；andothersspringfromtheaorta，strongandcontinuous。Andtothemiddleofeachofthetwokidneysisattachedahollowsinewyvein，stretchingrightalongthespinethroughthenarrows；byandbytheseveinsarelostineitherloin，andagainbecomevisibleextendingtotheflank。Andtheseoff-branchingsoftheveinsterminateinthebladder。
Forthebladderliesattheextremity，andisheldinpositionbytheductsstretchingfromthekidneys，alongthestalkthatextendstotheurethra；andprettywellallrounditisfastenedbyfinesinewymembranes，thatresembletosomeextentthethoracicdiaphragm。Thebladderinmanis，proportionatelytohissize，tolerablylarge。
Tothestalkofthebladdertheprivatepartisattached，theexternalorificescoalescing；butalittlelowerdown，oneoftheopeningscommunicateswiththetesticlesandtheotherwiththebladder。Thepenisisgristlyandsinewyinitstexture。Withitareconnectedthetesticlesinmaleanimals，andthepropertiesoftheseorgansweshalldiscussinourgeneralaccountofthesaidorgan。
Alltheseorgansaresimilarinthefemale；forthereisnodifferenceinregardtotheinternalorgans，exceptinrespecttothewomb，andwithreferencetotheappearanceofthisorganImustreferthereadertodiagramsinmy'Anatomy'。Thewomb，however，issituatedoverthebowel，andthebladderliesoverthewomb。Butwemusttreatbyandbyinourpagesofthewombofallfemaleanimalsviewedgenerally。Forthewombsofallfemaleanimalsarenotidentical，neitherdotheirlocaldispositionscoincide。
Thesearetheorgans，internalandexternal，ofman，andsuchistheirnatureandsuchtheirlocaldisposition。
BookII
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Withregardtoanimalsingeneral，somepartsororgansarecommontoall，ashasbeensaid，andsomearecommononlytoparticulargenera；theparts，moreover，areidenticalwithordifferentfromoneanotheronthelinesalreadyrepeatedlylaiddown。Forasageneralruleallanimalsthataregenericallydistincthavethemajorityoftheirpartsororgansdifferentinformorspecies；andsomeofthemtheyhaveonlyanalogicallysimilaranddiverseinkindorgenus，whiletheyhaveothersthatarealikeinkindbutspecificallydiverse；andmanypartsororgansexistinsomeanimals，butnotinothers。
Forinstance，viviparousquadrupedshaveallaheadandaneck，andallthepartsororgansofthehead，buttheydiffereachfromotherintheshapesoftheparts。Thelionhasitsneckcomposedofonesingleboneinsteadofvertebrae；but，whendissected，theanimalisfoundinallinternalcharacterstoresemblethedog。
Thequadrupedalviviparainsteadofarmshaveforelegs。Thisistrueofallquadrupeds，butsuchofthemashavetoeshave，practicallyspeaking，organsanalogoustohands；atallevents，theyusethesefore-limbsformanypurposesashands。Andtheyhavethelimbsontheleft-handsidelessdistinctfromthoseontherightthanman。
Thefore-limbsthenservemoreorlessthepurposeofhandsinquadrupeds，withtheexceptionoftheelephant。Thislatteranimalhasitstoessomewhatindistinctlydefined，anditsfrontlegsaremuchbiggerthanitshinderones；itisfive-toed，andhasshortanklestoitshindfeet。Butithasanosesuchinpropertiesandsuchinsizeastoallowofitsusingthesameforahand。Foriteatsanddrinksbyliftingupitsfoodwiththeaidofthisorganintoitsmouth，andwiththesameorganitliftsuparticlestothedriveronitsback；withthisorganitcanpluckuptreesbytheroots，andwhenwalkingthroughwateritspoutsthewaterupbymeansofit；andthisorganiscapableofbeingcrookedorcoiledatthetip，butnotofflexinglikeajoint，foritiscomposedofgristle。
Ofallanimalsmanalonecanlearntomakeequaluseofbothhands。
Allanimalshaveapartanalogoustothechestinman，butnotsimilartohis；forthechestinmanisbroad，butthatofallotheranimalsisnarrow。Moreover，nootheranimalbutmanhasbreastsinfront；theelephant，certainly，hastwobreasts，nothoweverinthechest，butnearit。
Moreover，also，animalshavetheflexionsoftheirforeandhindlimbsindirectionsoppositetooneanother，andindirectionsthereverseofthoseobservedinthearmsandlegsofman；withtheexceptionoftheelephant。Inotherwords，withtheviviparousquadrupedsthefrontlegsbendforwardsandthehindonesbackwards，andtheconcavitiesofthetwopairsoflimbsthusfaceoneanother。
Theelephantdoesnotsleepstanding，assomewerewonttoassert，butitbendsitslegsandsettlesdown；onlythatinconsequenceofitsweightitcannotbenditslegonbothsidessimultaneously，butfallsintoarecumbentpositionononesideortheother，andinthispositionitgoestosleep。Anditbendsitshindlegsjustasamanbendshislegs。
Inthecaseoftheovipara，asthecrocodileandthelizardandthelike，bothpairsoflegs，foreandhind，bendforwards，withaslightswerveononeside。Theflexionissimilarinthecaseofthemultipeds；onlythatthelegsinbetweentheextremeendsalwaysmoveinamannerintermediatebetweenthatofthoseinfrontandthosebehind，andaccordinglybendsidewaysratherthanbackwardsorforwards。Butmanbendshisarmsandhislegstowardsthesamepoint，andthereforeinoppositeways:thatistosay，hebendshisarmsbackwards，withjustaslightinclinationinwards，andhislegsfrontwards。Noanimalbendsbothitsfore-limbsandhind-limbsbackwards；butinthecaseofallanimalstheflexionoftheshouldersisintheoppositedirectiontothatoftheelbowsorthejointsoftheforelegs，andtheflexureinthehipstothatofthekneesofthehind-legs:sothatsincemandiffersfromotheranimalsinflexion，thoseanimalsthatpossesssuchpartsasthesemovethemcontrariwisetoman。
Birdshavetheflexionsoftheirlimbslikethoseofthequadrupeds；for，althoughbipeds，theybendtheirlegsbackwards，andinsteadofarmsorfrontlegshavewingswhichbendfrontwards。
Thesealisakindofimperfectorcrippledquadruped；forjustbehindtheshoulder-bladeitsfrontfeetareplaced，resemblinghands，likethefrontpawsofthebear；fortheyarefurnishedwithfivetoes，andeachofthetoeshasthreeflexionsandanailofinconsiderablesize。Thehindfeetarealsofurnishedwithfivetoes；intheirflexionsandnailstheyresemblethefrontfeet，andinshapetheyresembleafish'stail。