Moreover，moresemenmustneedsbeusedingenerationbythelargeranimal，andlittlebythesmaller。Thereforemanysmallonesmaybeproducedtogether，butitishardformanylargeonestobeso，andtothoseintermediateinsizeNaturehasassignedtheintermediatenumber。Wehaveformerlygiventhereasonwhysomeanimalsarelarge，somesmaller，andsomebetweenthetwo，andspeakinggenerally，withregardtothenumberofyoungproduced，thesolid—hoofedproduceone，thecloven—footedfew，themany—toedmany。（Thereasonofthisisthat，generallyspeaking，theirsizescorrespondtothisdifference。）Itisnotso，however，inallcases；foritisthelargenessandsmallnessofthebodythatiscauseoffewormanyyoungbeingborn，notthefactthatthekindofanimalhasone，two，ormanytoes。Aproofofthisisthattheelephantisthelargestofanimalsandyetismany—toed，andthecamel，thenextlargest，iscloven—footed。Andnotonlyinanimalsthatwalkbutalsointhosethatflyorswimthelargeonesproducefew，thesmallmany，forthesamereason。Inlikemanneralsoitisnotthelargestplantsthatbearmostfruit。
　　Wehaveexplainedthenwhysomeanimalsnaturallyproducemanyyoung，somebutfew，andsomeonlyone；inthedifficultynowstatedwemayratherbesurprisedwithreasonatthosewhichproducemany，sincesuchanimalsareoftenseentoconceivefromasinglecopulation。Whetherthesemenofthemalecontributestothematerialoftheembryobyitselfbecomingapartofitandmixingwiththesemenofthefemale，orwhether，aswesay，itdoesnotactinthiswaybutbringstogetherandfashionsthematerialwithinthefemaleandthegenerativesecretionasthefig—juicedoestheliquidsubstanceofmilk，whatisthereasonwhyitdoesnotformasingleanimalofconsiderablesize？Forcertainlyintheparallelcasethefig—juiceisnotseparatedifithastocurdlealargequantityofmilk，butthemorethemilkandthemorethefig—juiceputintoit，somuchthegreateristhecurdledmass。Nowitisnousetosaythattheseveralregionsoftheuterusattractthesemenandthereforemoreyoungthanoneareformed，becausetheregionsaremanyandthecotyledonsaremorethanone。Fortwoembryosareoftenformedinthesameregionoftheuterus，andtheymaybeseenlyinginarowinanimalsthatproducemany，whentheuterusisfilledwiththeembryos。（Thisisplainfromthedissections。）Ratherthetruthisthis。Asanimalscompletetheirgrowththerearecertainlimitstotheirsize，bothupwardsanddownwards，beyondwhichtheycannotgo，butitisinthespacebetweentheselimitsthattheyexceedorfallshortofoneanotherinsize，anditiswithintheselimitsthatoneman（oranyotheranimal）islargerorsmallerthananother。Soalsothegenerativematerialfromwhicheachanimalisformedisnotwithoutaquantitativelimitinbothdirections，norcanitbeformedfromanyquantityyouplease。Wheneverthenananimal，forthecauseassigned，dischargesmoreofthefemalesecretionthanisneededforbeginningtheexistenceofasingleanimal，itisnotpossiblethatonlyoneshouldbeformedoutofallthis，butanumberlimitedbytheappropriatesizeineachcase；norwillthesemenofthemale，orthepowerresidinginthesemen，formanythingeithermoreorlessthanwhatisaccordingtoNature。Inlikemanner，ifthemaleemitsmoresementhanisnecessary，ormorepowersindifferentpartsofthesemenasitisdivided，howevermuchitisitwillnotmakeanythinggreater；onthecontraryitwilldryupthematerialofthefemaleanddestroyit。Sofirealsodoesnotcontinuetomakewaterhotterinproportionasitisitselfincreased，butthereisafixedlimittotheheatofwhichwateriscapable；ifthatisoncereachedandthefireisthenincreased，thewaternolongergetshotterbutratherevaporatesandatlastdisappearsandisdriedup。Nowsinceitappearsthatthesecretionofthefemaleandthatfromthemaleneedtostandinsomeproportionaterelationtooneanother（Imeaninanimalsofwhichthemaleemitssemen），whathappensinthosethatproducemanyyoungisthis：fromtheveryfirstthesemenemittedbythemalehaspower，beingdivided，toformseveralembryos，andthematerialcontributedbythefemaleissomuchthatseveralcanbeformedoutofit。（Theparallelofcurdlingmilk，whichwespokeofbefore，isnolongerinpointhere，forwhatisformedbytheheatofthesemenisnotonlyofacertainquantitybutalsoofacertainquality，whereaswithfig—juiceandrennetquantityaloneisconcerned。）Thisthenisjustthereasonwhyinsuchanimalstheembryosformedarenumerousanddonotalluniteintoonewhole；itisbecauseanembryoisnotformedoutofanyquantityyouplease，butwhetherthereistoomuchortoolittle，ineithercasetherewillbenoresult，forthereisalimitsetaliketothepoweroftheheatwhichactsonthematerialandtothematerialsoactedupon。
　　Onthesameprinciplemanyembryosarenotformed，thoughthesecretionismuch，inthelargeanimalswhichproduceonlyoneyoungone，forinthemalsoboththematerialandthatwhichworksuponitareofacertainquantity。Sothentheydonotsecretesuchmaterialintoogreatquantityforthereasonpreviouslystated，andwhattheydosecreteisnaturallyjustenoughforoneembryoalonetobeformedfromit。Ifevertoomuchissecreted，thentwinsareborn。
　　Hencesuchcasesseemtobemoreportentous，becausetheyarecontrarytothegeneralandcustomaryrule。
　　Manbelongstoallthreeclasses，forheproducesoneonlyandsometimesmanyorfew，thoughnaturallyhealmostalwaysproducesone。
　　Becauseofthemoistureandheatofhisbodyhemayproducemany[forsemenisnaturallyfluidandhot]，butbecauseofhissizeheproducesfeworone。Onaccountofthisitresultsthatinmanaloneamonganimalstheperiodofgestationisirregular；whereastheperiodisfixedintherest，thereareseveralperiodsinman，forchildrenarebornatsevenmonthsandattenmonthsandatthetimesbetween，foreventhoseofeightmonthsdolivethoughlessoftenthantherest。Thereasonmaybegatheredfromwhathasjustbeensaid，andthequestionhasbeendiscussedintheProblems。Letthisexplanationsufficeforthesepoints。
　　ThecausewhythepartsmaybemultipliedcontrarytoNatureisthesameasthecauseofthebirthoftwins。Forthereasonexistsalreadyintheembryo，wheneveritaggregatesmorematerialatanypointofitselfthanisrequiredbythenatureofthepart。Theresultisthenthateitheroneofitspartsislargerthantheothers，asafingerorhandorfootoranyoftheotherextremitiesorlimbs；oragainiftheembryoisclefttheremaycomeintobeingmorethanonesuchpart，aseddiesdoinrivers；asthewaterintheseiscarriedalongwithacertainmotion，ifitdashagainstanythingtwosystemsoreddiescomeintobeingoutofone，eachretainingthesamemotion；thesamethinghappensalsowiththeembryos。Theabnormalpartsgenerallyareattachednearthosetheyresemble，butsometimesatadistancebecauseofthemovement—takingplaceintheembryo，andespeciallybecauseoftheexcessofmaterialreturningtothatplacewhenceitwastakenawaywhileretainingtheformofthatpartwhenceitaroseasasuperfluity。
　　Incertaincaseswefindadoublesetofgenerativeorgans[onemaleandtheotherfemale]。Whensuchduplicationoccurstheoneisalwaysfunctionalbutnottheother，becauseitisalwaysinsufficientlysuppliedwithnourishmentasbeingcontrarytoNature；itisattachedlikeagrowth（forsuchgrowthsalsoreceivenourishmentthoughtheyarealaterdevelopmentthanthebodyproperandcontrarytoNature。）Iftheformativepowerprevails，botharesimilar；ifitisaltogethervanquished，botharesimilar；butifitprevailhereandbevanquishedthere，thentheoneisfemaleandtheothermale。（Forwhetherweconsiderthereasonwhythewholeanimalismaleorfemale，orwhythepartsareso，makesnodifference。）
　　Whenwemeetwithdeficiencyinsuchparts，e。g。anextremityoroneoftheothermembers，wemustassumethesamecauseaswhentheembryoisaltogetheraborted（abortionofembryoshappensfrequently）。
　　Outgrowthsdifferfromtheproductionofmanyyounginthemannerstatedbefore；monstersdifferfromtheseinthatmostofthemareduetoembryosgrowingtogether。Somehoweverarealsoofthefollowingkind，whenthemonstrosityaffectsgreaterandmoresovereignparts，asforinstancesomemonstershavetwospleensormorethantwokidneys。Further，thepartsmaymigrate，themovementswhichformtheembryobeingdivertedandthematerialchangingitsplace。Wemustdecidewhetherthemonstrousanimalisoneoriscomposedofseveralgrowntogetherbyconsideringthevitalprinciple；thus，iftheheartisapartofsuchakindthenthatwhichhasoneheartwillbeoneanimal，themultipliedpartsbeingmereoutgrowths，butthosewhichhavemorethanoneheartwillbetwoanimalsgrowntogetherthroughtheirembryoshavingbeenconfused。
　　Italsooftenhappenseveninmanyanimalsthatdonotseemtobedefectiveandwhosegrowthisnowcomplete，thatsomeoftheirpassagesmayhavegrowntogetherorothersmayhavebeendivertedfromthenormalcourse。Thusinsomewomenbeforenowtheosuterihasremainedclosed，sothatwhenthetimeforthecatameniahasarrivedpainhasattackedthem，tilleitherthepassagehasburstopenofitsownaccordorthephysicianshaveremovedtheimpediment；somesuchcaseshaveendedindeathiftherupturehasbeenmadetooviolentlyorifithasbeenimpossibletomakeitatall。Insomeboysontheotherhandtheendofthepenishasnotcoincidedwiththeendofthepassagewheretheurineisvoided，butthepassagehasendedbelow，sothattheycrouchsittingtovoidit，andifthetestesaredrawnuptheyappearfromadistancetohavebothmaleandfemalegenerativeorgans。Thepassageofthesolidfoodalsohasbeenclosedbeforenowinsheepandsomeotheranimals；therewasacowinPerinthuswhichpassedfinematter，asifitweresifted，throughthebladder，andwhentheanuswascutopenitquicklyclosedupagainnorcouldtheysucceedinkeepingitopen。
　　Wehavenowspokenoftheproductionoffewandmanyyoung，andoftheoutgrowthofsuperfluouspartsoroftheirdeficiency，andalsoofmonstrosities。
　　5
　　Superfoetationdoesnotoccuratallinsomeanimalsbutdoesinothers；oftheformersomeareabletobringthelaterformedembryotobirth，whileotherscanonlydososometimes。Thereasonwhyitdoesnotoccurinsomeisthattheyproduceonlyoneyoungone，foritisnotfoundinsolid—hoofedanimalsandthoselargerthanthese，asowingtotheirsizethesecretionofthefemaleisallusedupfortheoneembryo。Forallthesehavelargebodies，andwhenananimalislargeitsfoetusislargeinproportion，e。g。thefoetusoftheelephantisasbigasacalf。Butsuperfoetationoccursinthosewhichproducemanyyoungbecausetheproductionofmorethanoneatabirthisitselfasortofsuperfoetation，onebeingaddedtoanother。Oftheseallthatarelarge，asman，bringtobirththelaterembryo，ifthesecondimpregnationtakesplacesoonafterthefirst，forsuchaneventhasbeenobservedbeforenow。Thereasonisthatgivenabove，foreveninasingleactofintercoursethesemendischargedismorethanenoughforoneembryo，andthisbeingdividedcausesmorethanonechildtobeborn，theoneofwhichislaterthantheother。Butwhentheembryohasalreadygrowntosomesizeanditsohappensthatcopulationoccursagain，superfoetationsometimestakesplace，butrarely，sincetheuterusgenerallyclosesinwomenduringtheperiodofgestation。Ifthiseverhappens（forthisalsohasoccurred）themothercannotbringthesecondembryotoperfection，butitiscastoutinastatelikewhatarecalledabortions。Forjustas，inthoseanimalsthatbearonlyone，allthesecretionofthefemaleisconvertedtothefirstformedembryobecauseofitssize，soitisherealso；theonlydifferenceisthatintheformercasethishappensatonce，inthelatterwhenthefoetushasattainedtosomesize，forthentheyareinthesamestateasthosethatbearonlyone。Inlikemanner，sincemannaturallywouldproducemanyyoung，andsincethesizeoftheuterusandthequantityofthefemalesecretionarebothgreaterthanisnecessaryforoneembryo，onlynotsomuchsoastobringtobirthasecond，thereforewomenandmaresaretheonlyanimalswhichadmitthemaleduringgestation，theformerforthereasonstated，andmaresbothbecauseofthebarrennessoftheirnatureandbecausetheiruterusisofsuperfluoussize，toolargeforonebuttoosmalltoallowasecondembryotobebroughttoperfectionbysuperfoetation。Andthemareisnaturallyinclinedtosexualintercoursebecausesheisinthesamecaseasthebarrenamongwomen；theselatterarebarrenbecausetheyhavenomonthlydischarge（whichcorrespondstotheactofintercourseinmales）andmareshaveexceedinglylittle。Andinalltheviviparathebarrenfemalesaresoinclined，becausetheyresemblethemaleswhenthesemenhascollectedinthetestesbutisnotbeinggotridof。Forthedischargeofthecatameniaisinfemalesasortofemissionofsemen，theybeingunconcoctedsemenashasbeensaidbefore。Henceitisthatthosewomenalsowhoareincontinentinregardtosuchintercourseceasefromtheirpassionforitwhentheyhavebornemanychildren，for，theseminalsecretionbeingthendrainedoff，theynolongerdesirethisintercourse。Andamongbirdsthehensarelessdisposedthatwaythanthecocks，becausetheuterusofthehen—birdisupnearthehypozoma；butwiththecock—birdsitistheotherway，fortheirtestesaredrawnupwithinthem，sothat，ifanykindofsuchbirdshasmuchsemennaturally，itisalwaysinneedofthisintercourse。Infemalesthenitencouragescopulationtohavetheuteruslowdown，butinmalestohavethetestesdrawnup。
　　Ithasbeennowstatedwhysuperfoetationisnotfoundinsomeanimalsatall，whyitisfoundinotherswhichsometimesbringthelaterembryostobirthandsometimesnot，andwhysomesuchanimalsareinclinedtosexualintercoursewhileothersarenot。
　　Someofthoseanimalsinwhichsuperfoetationoccurscanbringtheembryostobirthevenifalongtimeelapsesbetweenthetwoimpregnations，iftheirkindisspermatic，iftheirbodyisnotofalargesize，andiftheybearmanyyoung。Forbecausetheybearmanytheiruterusisspacious，becausetheyarespermaticthegenerativedischargeiscopious，andbecausethebodyisnotlargebutthedischargeisexcessiveandingreatermeasurethanisrequiredforthenourishmentwantedfortheembryo，thereforetheycannotonlyformanimalsbutalsobringthemtobirthlateron。Further，theuterusinsuchanimalsdoesnotcloseupduringgestationbecausethereisaquantityoftheresidualdischargeleftover。Thishashappenedbeforenoweveninwomen，forinsomeofthemthedischargecontinuesduringallthetimeofpregnancy。Inwomen，however，thisiscontrarytoNature，sothattheembryosuffers，butinsuchanimalsitisaccordingtoNature，fortheirbodyissoformedfromthebeginning，aswithhares。Forsuperfoetationoccursintheseanimals，sincetheyarenotlargeandtheybearmanyyoung（fortheyhavemanytoesandthemany—toedanimalsbearmany），andtheyarespermatic。Thisisshownbytheirhairiness，forthequantityoftheirhairisexcessive，theseanimalsalonehavinghairunderthefeetandwithinthejaws。Nowhairinessisasignofabundanceofresidualmatter，whereforeamongmenalsothehairyaregiventosexualintercourseandhavemuchsemenratherthanthesmooth。Inthehareitoftenhappensthatsomeoftheembryosareimperfectwhileothersofitsyoungareproducedperfect。
　　6
　　Someoftheviviparaproducetheiryoungimperfect，othersperfect；theone—hoofedandcloven—footedperfect，mostofthemany—toedimperfect。Thereasonofthisisthattheone—hoofedproduceoneyoungone，andthecloven—footedeitheroneortwogenerallyspeaking；nowitiseasytobringthefewtoperfection。Allthemany—toedanimalsthatbeartheiryoungimperfectgivebirthtomany。Hence，thoughtheyareabletonourishtheembryoswhilenewlyformed，theirbodiesareunabletocompletetheprocesswhentheembryoshavegrownandacquiredsomesize。Sotheyproducethemimperfect，likethoseanimalswhichgenerateascolex，forsomeofthemwhenbornarescarcelybroughtintoformatall，asthefox，bear，andlion，andsomeoftherestinlikemanner；andnearlyallofthemareblind，asnotonlytheanimalsmentionedbutalsothedog，wolf，andjackal。Thepigaloneproducesbothmanyandperfectyoung，andthusherealonewefindanyoverlapping；itproducesmanyasdothemany—toedanimals，butiscloven—footedorsolid—hoofed（fortherecertainlyaresolid—hoofedswine）。Theybear，then，manyyoungbecausethenutrimentwhichwouldotherwisegotoincreasetheirsizeisdivertedtothegenerativesecretion（forconsideredasasolid—hoofedanimalthepigisnotalargeone），andalsoitismoreoftencloven—hoofed，strivingasitwerewiththenatureofthesolid—hoofedanimals。Forthisreasonitproducessometimesonlyone，sometimestwo，butgenerallymany，andbringsthemtoperfectionbeforebirthbecauseofthegoodconditionofitsbody，beinglikearichsoil—whichhassufficientandabundantnutrimentforplants。
　　Theyoungofsomebirdsalsoarehatchedimperfect，thatistosayblind；thisappliestoallsmallbirdswhichlaymanyeggs，ascrowsandrooks，jays，sparrows，swallows，andtoallthosewhichlayfeweggswithoutproducingabundantnourishmentalongwiththeyoung，asring—doves，turtle—doves，andpigeons。Henceiftheeyesofswallowswhilestillyoungbeputouttheyrecovertheirsightagain，forthebirdsarestilldeveloping，notyetdeveloped，whentheinjuryisinflicted，sothattheeyesgrowandsproutafresh。Andingeneraltheproductionofyoungbeforetheyareperfectisowingtoinabilitytocontinuenourishingthem，andtheyarebornimperfectbecausetheyareborntoosoon。Thisisplainalsowithseven—monthschildren，forsincetheyarenotperfecteditoftenhappensthateventhepassages，e。g。oftheearsandnostrils，arenotyetopenedinsomeofthematbirth，butonlyopenlaterastheyaregrowing，andmanysuchinfantssurvive。
　　Inmanmalesaremoreoftenborndefectivethanfemales，butintheotheranimalsthisisnotthecase。Thereasonisthatinmanthemaleismuchsuperiortothefemaleinnaturalheat，andsothemalefoetusmovesaboutmorethanthefemale，andonaccountofmovingismoreliabletoinjury，forwhatisyoungiseasilyinjuredsinceitisweak。Forthissamereasonalsothefemalefoetusisnotperfectedequallywiththemaleinman（buttheyaresointheotheranimals，forinthemthefemaleisnotlaterindevelopingthanthemale）。Forwhilewithinthemotherthefemaletakeslongerindeveloping，butafterbirtheverythingisperfectedmorequicklyinfemalesthaninmales；Imean，forinstance，puberty，theprimeoflife，andoldage。Forfemalesareweakerandcolderinnature，andwemustlookuponthefemalecharacterasbeingasortofnaturaldeficiency。Accordinglywhileitiswithinthemotheritdevelopsslowlybecauseofitscoldness（fordevelopmentisconcoction，anditisheatthatconcocts，andwhatishotteriseasilyconcocted）；butafterbirthitquicklyarrivesatmaturityandoldageonaccountofitsweakness，forallinferiorthingscomesoonertotheirperfectionorend，andasthisistrueofworksofartsoitisofwhatisformedbyNature。Forthereasonjustgivenalsotwinsarelesslikelytosurviveinmanifonebemaleandonefemale，butthisisnotatallsointheotheranimals；forinmanitiscontrarytoNaturethattheyshouldrunanequalcourse，astheirdevelopmentdoesnottakeplaceinequalperiods，butthemalemustneedsbetoolateorthefemaletooearly；intheotheranimals，however，itisnotcontrarytoNature。Adifferenceisalsofoundbetweenmanandtheotheranimalsinrespectofgestation，foranimalsareinbetterbodilyconditionmostofthetime，whereasinmostwomengestationisattendedwithdiscomfort。Theirwayoflifeispartlyresponsibleforthis，forbeingsedentarytheyarefullofmoreresidualmatter；amongnationswherethewomenlivealaboriouslifegestationisnotequallyconspicuousandthosewhoareaccustomedtoworkbearchildreneasilyboththereandelsewhere；forworkconsumestheresidualmatter，butthosewhoaresedentaryhaveagreatdealofitinthembecausenotonlyistherenomonthlydischargeduringpregnancybutalsotheydonowork；thereforetheirtravailispainful。Butworkexercisesthemsothattheycanholdtheirbreath，uponwhichdependstheeaseordifficultyofchild—birth。
　　Thesecircumstancesthen，aswehavesaid，contributetocausethedifferencebetweenwomenandtheotheranimalsinthisstate，butthemostimportantthingisthis：insomeanimalsthedischargecorrespondingtothecatameniaisbutsmall，andinsomenotvisibleatall，butinwomenitisgreaterthaninanyotheranimal，sothatwhenthisdischargeceasesowingtopregnancytheyaretroubled（foriftheyarenotpregnanttheyareafflictedwithailmentswheneverthecatameniadonotoccur）；andtheyaremoretroubledasaruleatthebeginningofpregnancy，fortheembryoisableindeedtostopthecatameniabutistoosmallatfirsttoconsumeanyquantityofthesecretion；lateronittakesupsomeofitandsoalleviatesthemother。Intheotheranimals，onthecontrary，theresidualmatterisbutsmallandsocorrespondswiththegrowthofthefoetus，andasthesecretionswhichhindernourishmentarebeingconsumedbythefoetusthemotherisinbetterbodilyconditionthanusual。Thesameholdsgoodalsowithaquaticanimalsandbirds。Ifiteverhappensthatthebodyofthemotherisnolongeringoodconditionwhenthefoetusisnowbecominglarge，thereasonisthatitsgrowthneedsmorenourishmentthantheresidualmattersupplies。（Insomefewwomenithappensthatthebodyisinabetterstateduringpregnancy；
　　thesearewomeninwhosebodytheresidualmatterissmallsothatitisallusedupalongwiththenourishmentthatgoestothefoetus。）
　　7
　　Wemustalsospeakofwhatisknownasmolauteri，whichoccursrarelyinwomenbutstillisfoundsometimesduringpregnancy。Fortheyproducewhatiscalledamola；ithashappenedbeforenowtoawoman，aftershehadhadintercoursewithherhusbandandsupposedshehadconceived，thatatfirstthesizeofherbellyincreasedandeverythingelsehappenedaccordingly，butyetwhenthetimeforbirthcameon，sheneitherboreachildnorwashersizereduced，butshecontinuedthusforthreeorfouryearsuntildysenterycameon，endangeringherlife，andsheproducedalumpoffleshwhichiscalledmola。Moreoverthisconditionmaycontinuetilloldageanddeath。Suchmasseswhenexpelledfromthebodybecomesohardthattheycanhardlybecutthroughevenbyiron。ConcerningthecauseofthisphenomenonwehavespokenintheProblems；thesamethinghappenstotheembryointhewombastomeatshalfcookedinroasting，anditisnotduetoheat，assomesay，butrathertotheweaknessofthematernalheat。（Fortheirnatureseemstobeincapable，andunabletoperfectortoputthelasttouchestotheprocessofgeneration。Henceitisthatthemolaremainsinthemtilloldageoratanyrateforalongtime，forinitsnatureitisneitherperfectnoraltogetheraforeignbody。）Itiswantofconcoctionthatisthereasonofitshardness，aswithhalf—cookedmeat，forthishalf—dressingofmeatisalsoasortofwantofconcoction。
　　Adifficultyisraisedastowhythisdoesnotoccurinotheranimals，unlessindeeditdoesoccurandhasentirelyescapedobservation。Wemustsupposethereasontobethatwomanaloneamonganimalsissubjecttotroublesoftheuterus，andalonehasasuperfluousamountofcatameniaandisunabletoconcoctthem；when，then，theembryohasbeenformedofaliquidhardtoconcoct，thencomestheso—calledmolaintobeing，andthishappensnaturallyinwomenaloneoratanyratemorethaninotheranimals。
　　8
　　Milkisformedinthefemalesofallinternallyviviparousanimals，becomingusefulforthetimeofbirth。ForNaturehasmadeitforthesakeofthenourishmentofanimalsafterbirth，sothatitmayneitherfailatthistimeatallnoryetbeatallsuperfluous；thisisjustwhatwefindhappening，unlessanythingchancecontrarytoNature。Intheotheranimalstheperiodofgestationdoesnotvary，andsothemilkisconcoctedintimetosuitthismoment，butinman，sincethereareseveraltimesofbirth，itmustbereadyatthefirstofthese；henceinwomenthemilkisuselessbeforetheseventhmonthandonlythenbecomesuseful。Thatitisonlyconcoctedatthelaststagesiswhatweshouldexpecttohappenalsoasbeingduetoanecessarycause。Foratfirstsuchresidualmatterwhensecretedisusedupforthedevelopmentoftheembryo；nowthenutritiouspartinallthingsisthesweetestandthemostconcocted，andthuswhenallsuchelementsareremovedwhatremainsmustbecomeofnecessitybitterandill—flavoured。Astheembryoisperfecting，theresidualmatterleftoverincreasesinquantitybecausethepartconsumedbytheembryoisless；itisalsosweetersincetheeasilyconcoctedpartislessdrawnawayfromit。Foritisnolongerexpendedonmouldingtheembryobutonlyonslightlyincreasingitsgrowth，itbeingnowfixedbecauseithasreachedperfection（forinasensethereisaperfectionevenofanembryo）。
　　Thereforeitcomesforthfromthemotherandchangesitsmodeofdevelopment，asnowpossessingwhatbelongstoit；andnolongertakesthatwhichdoesnotbelongtoit；anditisatthisseasonthatthemilkbecomesuseful。
　　Themilkcollectsintheupperpartofthebodyandthebreastsbecauseoftheoriginalplanoftheorganism。Forthepartabovethehypozomaisthesovereignpartoftheanimal，whilethatbelowisconcernedwithnourishmentandresidualmatter，inorderthatallanimalswhichmoveaboutmaycontainwithinthemselvesnourishmentenoughtomakethemindependentwhentheymovefromoneplacetoanother。Fromthisupperpartalsoisproducedthegenerativesecretionforthereasonmentionedintheopeningofourdiscussion。
　　Butboththesecretionofthemaleandthecatameniaofthefemaleareofasanguineousnature，andthefirstprincipleofthisbloodandoftheblood—vesselsistheheart，andtheheartisinthispartofthebody。Thereforeitisherethatthechangeofsuchasecretionmustfirstbecomeplain。Thisiswhythevoicechangesinbothsexeswhentheybegintobearseed（forthefirstprincipleofthevoiceresidesthere，andisitselfchangedwhenitsmovingcausechanges）。
　　Atthesametimethepartsaboutthebreastsareraisedvisiblyeveninmalesbutstillmoreinfemales，fortheregionofthebreastsbecomesemptyandspongyinthembecausesomuchmaterialisdrainedawaybelow。Thisissonotonlyinwomenbutalsointhoseanimalswhichhavethemammaelowdown。
　　Thischangeinthevoiceandthepartsaboutthemammaeisplaineveninothercreaturestothosewhohaveexperienceofeachkindofanimal，butismostremarkableinman。Thereasonisthatinmantheproductionofsecretionisgreatestinbothsexesinproportiontotheirsizeascomparedwithotheranimals；Imeanthatofthecatameniainwomenandtheemissionofsemeninmen。When，therefore，theembryonolongertakesupthesecretioninquestionbutyetpreventsitsbeingdischargedfromthemother，itisnecessarythattheresidualmattershouldcollectinallthoseemptypartswhicharesetuponthesamepassages。Andsuchisthepositionofthemammaeineachkindofanimalsforbothcauses；itissobothforthesakeofwhatisbestandofnecessity。
　　Itishere，then，thatthenourishmentinanimalsisnowformedandbecomesthoroughlyconcocted。Asforthecauseofconcoction，wemaytakethatalreadygiven，orwemaytaketheopposite，foritisareasonableviewalsothattheembryobeinglargertakesmorenourishment，sothatlessisleftoveraboutthistime，andthelessisconcoctedmorequickly。
　　Thatmilkhasthesamenatureasthesecretionfromwhicheachanimalisformedisplain，andhasbeenstatedpreviously。ForthematerialwhichnourishesisthesameasthatfromwhichNatureformstheanimalingeneration。Nowthisisthesanguineousliquidinthesanguinea，andmilkisbloodconcocted（notcorrupted；Empedocleseithermistookthefactormadeabadmetaphorwhenhecomposedtheline：’Onthetenthdayoftheeighthmonththemilkcomesintobeing，awhitepus’，forputrefactionandconcoctionareoppositethings，andpusisakindofputrefactionbutmilkisconcocted）。WhilewomenaresucklingchildrenthecatameniadonotoccuraccordingtoNature，nordotheyconceive；iftheydoconceive，themilkdriesup。Thisisbecausethenatureofthemilkandofthecatameniaisthesame，andNaturecannotbesoproductiveastosupplybothatonce；ifthesecretionisdivertedintheonedirectionitmustneedsceaseintheother，unlesssomeviolenceisdonecontrarytothegeneralrule。ButthisisasmuchastosaythatitiscontrarytoNature，forinallcaseswhereitisnotimpossibleforthingstobeotherwisethantheygenerallyarebutwheretheymaysohappen，stillwhatisthegeneralruleiswhatis’accordingtoNature’。
　　Thetimealsoatwhichtheyounganimalisbornhasbeenwellarranged。Forwhenthenourishmentcomingthroughtheumbilicalcordisnolongersufficientforthefoetusbecauseofitssize，thenatthesametimethemilkbecomesusefulforthenourishmentofthenewly—bornanimal，andtheblood—vesselsroundwhichtheso—calledumbilicalcordliesasacoatcollapseasthenourishmentisnolongerpassingthroughit；forthesereasonsitisatthattimealsothattheyounganimalentersintotheworld。
　　9
　　Thenaturalbirthofallanimalsishead—foremost，becausethepartsabovetheumbilicalcordarelargerthanthosebelow。Thebodythen，beingsuspendedfromthecordasinabalance，inclinestowardstheheavyend，andthelargerpartsaretheheavier。
　　10
　　Theperiodofgestationis，asamatteroffact，determinedgenerallyineachanimalinproportiontothelengthofitslife。Thisweshouldexpect，foritisreasonablethatthedevelopmentofthelong—livedanimalsshouldtakealongertime。Yetthisisnotthecauseofit，buttheperiodsonlycorrespondaccidentallyforthemostpart；forthoughthelargerandmoreperfectsanguineadolivealongtime，yetthelargerarenotalllonger—lived。Manlivesalongertimethananyanimalofwhichwehaveanycredibleexperienceexcepttheelephant，andyetthehumankindissmallerthanthatofthebushy—tailedanimalsandmanyothers。Therealcauseoflonglifeinanyanimalisitsbeingtemperedinamannerresemblingtheenvironingair，alongwithcertainothercircumstancesofitsnature，ofwhichwewillspeaklater；butthecauseofthetimeofgestationisthesizeoftheoffspring。Foritisnoteasyforlargemassestoarriveattheirperfectioninasmalltime，whethertheybeanimalsor，onemaysay，anythingelsewhatever。Thatiswhyhorsesandanimalsakintothem，thoughlivingashortertimethanman，yetcarrytheiryounglonger；forthetimeintheformerisayear，butinthelattertenmonthsattheoutside。Forthesamereasonalsothetimeislonginelephants；theycarrytheiryoungtwoyearsonaccountoftheirexcessivesize。
　　Wefind，aswemightexpect，thatinallanimalsthetimeofgestationanddevelopmentandthelengthoflifeaimsatbeingmeasuredbynaturallycompleteperiods。ByanaturalperiodImean，e。g。adayandnight，amonth，ayear，andthegreatertimesmeasuredbythese，andalsotheperiodsofthemoon，thatistosay，thefullmoonandherdisappearanceandthehalvesofthetimesbetweenthese，foritisbythesethatthemoon’sorbitfitsinwiththatofthesun[themonthbeingaperiodcommontoboth]。
　　Themoonisafirstprinciplebecauseofherconnexionwiththesunandherparticipationinhislight，beingasitwereasecondsmallersun，andthereforeshecontributestoallgenerationanddevelopment。Forheatandcoldvaryingwithincertainlimitsmakethingstocomeintobeingandafterthistoperish，anditisthemotionsofthesunandmoonthatfixthelimitbothofthebeginningandoftheendoftheseprocesses。Justasweseetheseaandallbodiesofwatersettlingandchangingaccordingtothemovementorrestofthewinds，andtheairandwindsagainaccordingtothecourseofthesunandmoon，soalsothethingswhichgrowoutoftheseorareinthesemustneedsfollowsuit。Foritisreasonablethattheperiodsofthelessimportantshouldfollowthoseofthemoreimportant。Forinasenseawind，too，hasalifeandbirthanddeath。
　　Asfortherevolutionsofthesunandmoon，theymayperhapsdependonotherprinciples。Itistheaim，then，ofNaturetomeasurethecomingintobeingandtheendofanimalsbythemeasureofthesehigherperiods，butshedoesnotbringthistopassaccuratelybecausemattercannotbeeasilybroughtunderruleandbecausetherearemanyprincipleswhichhindergenerationanddecayfrombeingaccordingtoNature，andoftencausethingstofalloutcontrarytoNature。
　　Wehavenowspokenofthenourishmentofanimalswithinthemotherandoftheirbirthintotheworld，bothofeachkindseparatelyandofallincommon。
　　BookV
　　1
　　WEmustnowinvestigatethequalitiesbywhichthepartsofanimalsdiffer。Imeansuchqualitiesofthepartsasbluenessandblacknessintheeyes，heightanddepthofpitchinthevoice，anddifferencesincolourwhetheroftheskinorofhairandfeathers。
　　Somesuchqualitiesarefoundtocharacterizethewholeofakindofanimalssometimes，whileinotherkindstheyoccuratrandom，asisespeciallythecaseinman。Further，inconnexionwiththechangesinthetimeoflife，allanimalsarealikeinsomepoints，butareopposedinothersasinthecaseofthevoiceandthecolourofthehair，forsomedonotgrowgreyvisiblyinoldage，whilemanissubjecttothismorethananyotheranimal。Andsomeoftheseaffectionsappearimmediatelyafterbirth，whileothersbecomeplainasageadvancesorinoldage。
　　Nowwemustnolongersupposethatthecauseoftheseandallsuchphenomenaisthesame。ForwheneverthingsarenottheproductofNatureworkingupontheanimalkingdomasawhole，noryetcharacteristicofeachseparatekind，thennoneofthesethingsissuchasitisorissodevelopedforanyfinalcause。Theeyeforinstanceexistsforafinalcause，butitisnotblueforafinalcauseunlessthisconditionbecharacteristicofthekindofanimal。
　　Infactinsomecasesthisconditionhasnoconnexionwiththeessenceoftheanimal’sbeing，butwemustreferthecausestothematerialandthemotiveprincipleorefficientcause，ontheviewthatthesethingscomeintobeingbyNecessity。For，aswassaidoriginallyintheoutsetofourdiscussion，whenwearedealingwithdefiniteandorderedproductsofNature，wemustnotsaythateachisofacertainqualitybecauseitbecomesso，butratherthattheybecomesoandsobecausetheyaresoandso，fortheprocessofBecomingordevelopmentattendsuponBeingandisforthesakeofBeing，notviceversa。
　　TheancientNature—philosophershowevertooktheoppositeview。
　　Thereasonofthisisthattheydidnotseethatthecauseswerenumerous，butonlysawthematerialandefficientanddidnotdistinguisheventhese，whiletheymadenoinquiryatallintotheformalandfinalcauses。
　　Everythingthenexistsforafinalcause，andallthosethingswhichareincludedinthedefinitionofeachanimal，orwhicheitheraremeanstoanendorareendsinthemselves，comeintobeingboththroughthiscauseandtherest。Butwhenwecometothosethingswhichcomeintobeingwithoutfallingundertheheadsjustmentioned，theircoursemustbesoughtinthemovementorprocessofcomingintobeing，ontheviewthatthedifferenceswhichmarkthemariseintheactualformationoftheanimal。Aneye，forinstance，theanimalmusthaveofnecessity（forthefundamentalideaoftheanimalisofsuchakind），butitwillhaveaneyeofaparticularkindofnecessityinanothersense，notthesensementionedjustabove，becauseitisitsnaturetoactorbeactedoninthisorthatway。
　　Thesedistinctionsbeingdrawnletusspeakofwhatcomesnextinorder。Assoonthenastheoffspringofallanimalsareborn，especiallythosebornimperfect，theyareinthehabitofsleeping，becausetheycontinuesleepingalsowithinthemotherwhentheyfirstacquiresensation。Butthereisadifficultyabouttheearliestperiodofdevelopment，whetherthestateofwakefulnessexistsinanimalsfirst，orthatofsleep。Sincetheyplainlywakeupmoreastheygrowolder，itisreasonabletosupposethattheoppositestate，thatofsleep，existsinthefirststagesofdevelopment。Moreoverthechangefromnotbeingtobeingmustpassthroughtheintermediatecondition，andsleepseemstobeinitsnaturesuchacondition，beingasitwereaboundarybetweenlivingandnotliving，andthesleeperbeingneitheraltogethernon—existentnoryetexistent。Forlifemostofallappertainstowakefulness，onaccountofsensation。Butontheotherhand，ifitisnecessarythattheanimalshouldhavesensationandifitisthenfirstananimalwhenithasacquiredsensation，weoughttoconsidertheoriginalconditiontobenotsleepbutonlysomethingresemblingsleep，suchaconditionaswefindalsoinplants，forindeedatthistimeanimalsdoactuallylivethelifeofaplant。Butitisimpossiblethatplantsshouldsleep，forthereisnosleepwhichcannotbebroken，andtheconditioninplantswhichisanalogoustosleepcannotbebroken。
　　Itisnecessarythenfortheembryoanimaltosleepmostofthetimebecausethegrowthtakesplaceintheupperpartofthebody，whichisconsequentlyheavier（andwehavestatedelsewherethatsuchisthecauseofsleep）。Butneverthelesstheyarefoundtowakeeveninthewomb（thisisclearindissectionsandintheovipara），andthentheyimmediatelyfallintoasleepagain。Thisiswhyafterbirthalsotheyspendmostoftheirtimeinsleep。
　　Whenawakeinfantsdonotlaugh，butwhileasleeptheybothlaughandcry。Foranimalshavesensationsevenwhileasleep，notonlywhatarecalleddreamsbutalsoothersbesidesdreams，asthosepersonswhoarisewhilesleepinganddomanythingswithoutdreaming。Fortherearesomewhogetupwhilesleepingandwalkaboutseeingjustlikethosewhoareawake；thesehaveperceptionofwhatishappening，andthoughtheyarenotawake，yetthisperceptionisnotlikeadream。Soinfantspresumablyhavesense—perceptionandliveintheirsleepowingtoprevioushabit，beingasitwerewithoutknowledgeofthewakingstate。Astimegoesonandtheirgrowthistransferredtothelowerpartofthebody，theynowwakeupmoreandspendmostoftheirtimeinthatcondition。
　　Childrencontinueasleepatfirstmorethanotheranimals，fortheyareborninamoreimperfectconditionthanotheranimalsthatareproducedinanythinglikeaperfectstate，andtheirgrowthhastakenplacemoreintheupperpartofthebody。
　　Theeyesofallchildrenarebluishimmediatelyafterbirth；laterontheychangetothecolourwhichistobetheirspermanently。Butinthecaseofotheranimalsthisisnotvisible。Thereasonofthisisthattheeyesofotheranimalsaremoreapttohaveonlyonecolourforeachkindofanimal；e。g。cattlearedark—eyed，theeyeofallsheepispale，ofothersagainthewholekindisblueorgrey—eyed，andsomeareyellow（goat—eyed），asthemajorityofgoatsthemselves，whereastheeyesofmenhappentobeofmanycolours，fortheyareblueorgreyordarkinsomecasesandyellowinothers。Hence，astheindividualsinotherkindsofanimalsdonotdifferfromoneanotherinthecolour，soneitherdotheydifferfromthemselves，fortheyarenotofanaturetohavemorethanonecolour。Oftheotheranimalsthehorsehasthegreatestvarietyofcolourintheeye，forsomeofthemareactuallyheteroglaucous；
　　thisphenomenonisnottobeseeninanyoftheotheranimals，butmanissometimesheteroglaucous。
　　Whythenisitthatthereisnovisiblechangeintheotheranimalsifwecomparetheirconditionwhennewlybornwiththeirconditionatamoreadvancedage，butthatthereissuchachangeinchildren？Wemustconsiderjustthistobeasufficientcause，thatthepartconcernedhasonlyonecolourintheformerbutseveralcoloursinthelatter。Andthereasonwhytheeyesofinfantsarebluishandhavenoothercolouristhatthepartsareweakerinthenewlybornandbluenessisasortofweakness。
　　Wemustalsogainageneralnotionaboutthedifferenceineyes，forwhatreasonsomeareblue，somegrey，someyellow，andsomedark。Tosupposethatthebluearefiery，asEmpedoclessays，whilethedarkhavemorewaterthanfireinthem，andthatthisiswhytheformer，theblue，havenotkeensightbyday，viz。owingtodeficiencyofwaterintheircomposition，andthelatterareinlikeconditionbynight，viz。owingtodeficiencyoffire—thisisnotwellsaidifindeedwearetoassumesighttobeconnectedwithwater，notfire，inallcases。Moreoveritispossibletorenderanotheraccountofthecauseofthecolours，butifindeedthefactisaswasstatedbeforeinthetreatiseonthesenses，andstillearlierthanthatintheinvestigationsconcerningsoul—ifthissenseorganiscomposedofwaterandifwewererightinsayingforwhatreasonitiscomposedofwaterandnotofairorfire—thenwemustassumethewatertobethecauseofthecoloursmentioned。Forsomeeyeshavetoomuchliquidtobeadaptedtothemovement，othershavetoolittle，othersthedueamount。Thoseeyesthereforeinwhichthereismuchliquidaredarkbecausemuchliquidisnottransparent，thosewhichhavelittleareblue；（sowefindintheseathatthetransparentpartofitappearslightblue，thelesstransparentwatery，andtheunfathomablewaterisdarkordeep—blueonaccountofitsdepth）。
　　Whenwecometotheeyesbetweenthese，theydifferonlyindegree。
　　Wemustsupposethesamecausealsotoberesponsibleforthefactthatblueeyesarenotkeen—sightedbydaynordarkeyesbynight。
　　Blueeyes，becausethereislittleliquidinthem，aretoomuchmovedbythelightandbyvisibleobjectsinrespectoftheirliquidityaswellastheirtransparency，butsightisthemovementofthispartinsofarasitistransparent，notinsofarasitisliquid。Darkeyesarelessmovedbecauseofthequantityofliquidinthem。Andsotheyseelesswellinthedusk，forthenocturnallightisweak；atthesametimealsoliquidisingeneralhardtomoveinthenight。Butiftheeyeistosee，itmustneithernotbemovedatallnoryetmorethaninsofarasitistransparent，forthestrongermovementdrivesouttheweaker。Henceitisthatonchangingfromstrongcolours，orongoingoutofthesunintothedark，mencannotsee，forthemotionalreadyexistingintheeye，beingstrong，stopsthatfromoutside，andingeneralneitherastrongnoraweaksightcanseebrightthingsbecausetheliquidisacteduponandmovedtoomuch。
　　Thesamethingisshownalsobythemorbidaffectionsofeachkindofsight。Cataractattackstheblue—eyedmore，butwhatiscalled’nyctalopia’thedark—eyed。Nowcataractisasortofdrynessoftheeyesandthereforeitisfoundmoreintheaged，forthispartalsoliketherestofthebodygetsdrytowardsoldage；butisanexcessofliquidityandsoisfoundmoreintheyounger，fortheirbrainismoreliquid。
　　Thesightoftheeyewhichisintermediatebetweentoomuchandtoolittleliquidisthebest，forithasneithertoolittlesoastobedisturbedandhinderthemovementofthecolours，nortoomuchsoastocausedifficultyofmovement。
　　Notonlytheabove—mentionedfactsarecausesofseeingkeenlyorthereverse，butalsothenatureoftheskinuponwhatiscalledthepupil。Thisoughttobetransparent，anditisnecessarythatthetransparentshouldbethinandwhiteandeven，thinthatthemovementcomingfromwithoutmaypassstraightthroughit，eventhatitmaynotcastashadetheliquidbehinditbywrinkling（forthisalsoisareasonwhyoldmenhavenotkeensight，theskinoftheeyeliketherestoftheskinwrinklingandbecomingthickerinoldage），andwhitebecauseblackisnottransparent，forthatisjustwhatismeantby’black’，whatisnotshonethrough，andthatiswhylanternscannotgivelightiftheybemadeofblackskin。Itisforthesereasonsthenthatthesightisnotkeeninoldagenorinthediseasesinquestion，butitisbecauseofthesmallamountofliquidthattheeyesofchildrenappearblueatfirst。
　　Andthereasonwhymenespeciallyandhorsesoccasionallyareheteroglaucousisthesameasthereasonwhymanalonegrowsgreyandthehorseistheonlyotheranimalwhosehairswhitenvisiblyinoldage。Forgreynessisaweaknessofthefluidinthebrainandanincapacitytoconcoctproperly，andsoisbluenessoftheeyes；excessofthinnessorofthicknessproducesthesameeffect，accordingasthisliquidityistoolittleortoomuch。WheneverthenNaturecannotmaketheeyescorrespondexactly，eitherbyconcoctingorbynotconcoctingtheliquidinboth，butconcoctstheoneandnottheother，thentheresultisheteroglaucia。
　　Thecauseofsomeanimalsbeingkeen—sightedandothersnotsoisnotsimplebutdouble。Fortheword’keen’hasprettymuchadoublesense（andthisisthecaseinlikemannerwithhearingandsmelling）。Inonesensekeensightmeansthepowerofseeingatadistance，inanotheritmeansthepowerofdistinguishingasaccuratelyaspossibletheobjectsseen。Thesetwofacultiesarenotnecessarilycombinedinthesameindividual。Forthesameperson，ifheshadeshiseyeswithhishandorlookthroughatube，doesnotdistinguishthedifferencesofcoloureithermoreorlessinanyway，buthewillseefurther；infact，meninpitsorwellssometimesseethestars。Thereforeifanyanimal’sbrowsprojectfarovertheeye，butiftheliquidinthepupilisnotpurenorsuitedtothemovementcomingfromexternalobjectsandiftheskinoverthesurfaceisnotthin，thisanimalwillnotdistinguishaccuratelythedifferencesofthecoloursbutitwillbeabletoseefromalongdistance（justasitcanfromashortone）betterthanthoseinwhichtheliquidandthecoveringmembranearepurebutwhichhavenobrowsprojectingovertheeyes。Forthecauseofseeingkeenlyinthesenseofdistinguishingthedifferencesisintheeyeitself；asonacleangarmentevensmallstainsarevisible，soalsoinapuresightevensmallmovementsareplainandcausesensation。Butitisthepositionoftheeyesthatisthecauseofseeingthingsfaroffandofthemovementsinthetransparentmediumcomingtotheeyesfromdistantobjects。Aproofofthisisthatanimalswithprominenteyesdonotseewellatadistance，whereasthosewhichhavetheireyeslyingdeepintheheadcanseethingsatadistancebecausethemovementisnotdispersedinspacebutcomesstraighttotheeye。
　　Foritmakesnodifferencewhetherwesay，assomedo，thatseeingiscausedbythesightgoingforthfromtheeye—onthatview，ifthereisnothingprojectingovertheeyes，thesightmustbescatteredandsolessofitwillfallontheobjectsofvisionandthingsatadistancewillnotbeseensowell—orwhetherwesaythatseeingisduetothemovementcomingfromtheobjects；forthesightalsomustsee，inamannerresemblingthemovement。Thingsatadistance，then，wouldbeseenbestiftherewere，sotosay，acontinuoustubestraightfromthesighttoitsobject，forthemovementfromtheobjectwouldnotthenbedissipated；but，ifthatisimpossible，stillthefurtherthetubeextendsthemoreaccuratelymustdistantobjectsbeseen。
　　Letthese，then，begivenasthecausesofthedifferenceineyes。
　　2
　　Itisthesamealsowithhearingandsmell；tohearandsmellaccuratelymeaninonesensetoperceiveaspreciselyaspossibleallthedistinctionsoftheobjectsofperception，inanothersensetohearandsmellfaroff。Aswithsight，soherethesense—organisthecauseofjudgingwellthedistinctions，ifboththatorganitselfandthemembranerounditbepure。Forthepassagesofallthesense—organs，ashasbeensaidinthetreatiseonsensation，runtotheheart，ortoitsanalogueincreaturesthathavenoheart。
　　Thepassageofthehearing，then，sincethissense—organisofair，endsattheplacewheretheinnatespirituscausesinsomeanimalsthepulsationoftheheartandinothersrespiration；whereforealsoitisthatweareabletounderstandwhatissaidandrepeatwhatwehaveheard，foraswasthemovementwhichenteredthroughthesense—organ，suchagainisthemovementwhichiscausedbymeansofthevoice，beingasitwereofoneandthesamestamp，sothatamancansaywhathehasheard。Andwehearlesswellduringayawnorexpirationthanduringinspiration，becausethestarting—pointofthesense—organofhearingissetuponthepartconcernedwithbreathingandisshakenandmovedastheorganmovesthebreath，forwhilesettingthebreathinmotionitismoveditself。Thesamethinghappensinwetweatheroradampatmosphere……Andtheearsseemedtobefilledwithairbecausetheirstarting—pointisneartheregionofbreathing。
　　Accuracytheninjudgingthedifferencesofsoundsandsmellsdependsonthepurityofthesense—organandofthemembranelyinguponitssurface，forthenallthemovementsbecomeclearinsuchcases，asinthecaseofsight。Perceptionandnon—perceptionatadistancealsodependonthesamethingswithhearingandsmellaswithsight。Forthoseanimalscanperceiveatadistancewhichhavechannels，sotosay，runningthroughthepartsconcernedandprojectingfarinfrontofthesense—organs。Thereforeallanimalswhosenostrilsarelong，astheLaconianhounds，arekeen—scented，forthesense—organbeingabovethem，themovementsfromadistancearenotdissipatedbutgostraighttothemark，justasthemovementswhichcausesightdowiththosewhoshadowtheeyeswiththehand。