第1章

byAristotletranslatedbyG。R。T。Ross1

WEmustnowtreatofyouthandoldageandlifeanddeath。Wemustprobablyalsoatthesametimestatethecausesofrespirationaswell，sinceinsomecaseslivingandthereversedependonthis。

Wehaveelsewheregivenapreciseaccountofthesoul，andwhileitisclearthatitsessentialrealitycannotbecorporeal，yetmanifestlyitmustexistinsomebodilypartwhichmustbeoneofthosepossessingcontroloverthemembers。Letusforthepresentsetasidetheotherdivisionsorfacultiesofthesoul（whicheverofthetwobethecorrectname）。Butastobeingwhatiscalledananimalandalivingthing，wefindthatinallbeingsendowedwithbothcharacteristics（viz。beingananimalandbeingalive）theremustbeasingleidenticalpartinvirtueofwhichtheyliveandarecalledanimals；forananimalquaanimalcannotavoidbeingalive。Butathingneednot，thoughalive，beanimal，forplantslivewithouthavingsensation，anditisbysensationthatwedistinguishanimalfromwhatisnotanimal。

Thisorgan，then，mustbenumericallyoneandthesameandyetpossessmultipleanddisparateaspects，forbeinganimalandlivingarenotidentical。Sincethentheorgansofspecialsensationhaveonecommonorganinwhichthesenseswhenfunctioningmustmeet，andthismustbesituatedmidwaybetweenwhatiscalledbeforeandbehind（wecall’before’thedirectionfromwhichsensationcomes，’behind’theopposite），further，sinceinalllivingthingsthebodyisdividedintoupperandlower（theyallhaveupperandlowerparts，sothatthisistrueofplantsaswell），clearlythenutritiveprinciplemustbesituatedmidwaybetweentheseregions。

Thatpartwherefoodenterswecallupper，consideringitbyitselfandnotrelativelytothesurroundinguniverse，whiledownwardisthatpartbywhichtheprimaryexcrementisdischarged。

Plantsarethereverseofanimalsinthisrespect。Tomaninparticularamongtheanimals，onaccountofhiserectstature，belongsthecharacteristicofhavinghisupperpartspointingupwardsinthesenseinwhichthatappliestotheuniverse，whileintheotherstheseareinanintermediateposition。Butinplants，owingtotheirbeingstationaryanddrawingtheirsustenancefromtheground，theupperpartmustalwaysbedown；forthereisacorrespondencebetweentherootsinaplantandwhatiscalledthemouthinanimals，bymeansofwhichtheytakeintheirfood，whetherthesourceofsupplybetheearthoreachother’sbodies。

2

Allperfectlyformedanimalsaretobedividedintothreeparts，onethatbywhichfoodistakenin，onethatbywhichexcrementisdischarged，andthethirdtheregionintermediatebetweenthem。Inthelargestanimalsthislatteriscalledthechestandintheotherssomethingcorresponding；insomealsoitismoredistinctlymarkedoffthaninothers。Allthosealsothatarecapableofprogressionhaveadditionalmemberssubservienttothispurpose，bymeansofwhichtheybearthewholetrunk，towitlegsandfeetandwhateverpartsarepossessedofthesamepowers。Nowitisevidentbothbyobservationandbyinferencethatthesourceofthenutritivesoulisinthemidstofthethreeparts。Formanyanimals，wheneitherpart—theheadorthereceptacleofthefood—iscutoff，retainlifeinthatmembertowhichthemiddleremainsattached。Thiscanbeseentooccurinmanyinsects，e。g。waspsandbees，andmanyanimalsalsobesidesinsectscan，thoughdivided，continuetolivebymeansofthepartconnectedwithnutrition。

Whilethismemberisindeedinactualitysingle，yetpotentiallyitismultiple，fortheseanimalshaveaconstitutionsimilartothatofPlants；plantswhencutintosectionscontinuetolive，andanumberoftreescanbederivedfromonesinglesource。Aseparateaccountwillbegivenofthereasonwhysomeplantscannotlivewhendivided，whileotherscanbepropagatedbythetakingofslips。Inthisrespect，however，plantsandinsectsarealike。

Itistruethatthenutritivesoul，inbeingspossessingit，whileactuallysinglemustbepotentiallyplural。Anditistoowiththeprincipleofsensation，forevidentlythedividedsegmentsoftheseanimalshavesensation。Theyareunable，however，topreservetheirconstitution，asplantscan，notpossessingtheorgansonwhichthecontinuanceoflifedepends，forsomelackthemeansforseizing，othersforreceivingtheirfood；oragaintheymaybedestituteofotherorgansaswell。

Divisibleanimalsarelikeanumberofanimalsgrowntogether，butanimalsofsuperiorconstructionbehavedifferentlybecausetheirconstitutionisaunityofthehighestpossiblekind。Hencesomeoftheorgansondivisiondisplayslightsensitivenessbecausetheyretainsomepsychicalsusceptibility；theanimalscontinuetomoveafterthevitalshavebeenabstracted：tortoises，forexample，dosoevenafterthehearthasbeenremoved。

3

Thesamephenomenonisevidentbothinplantsandinanimals，andinplantswenoteitbothintheirpropagationbyseedandingraftsandcuttings。Genesisfromseedsalwaysstartsfromthemiddle。Allseedsarebivalvular，andtheplaceofjunctionissituatedatthepointofattachment（totheplant），anintermediatepartbelongingtobothhalves。Itisfromthispartthatbothrootandstemofgrowingthingsemerge；thestarting—pointisinacentralpositionbetweenthem。Inthecaseofgraftsandcuttingsthisisparticularlytrueofthebuds；forthebudisinawaythestarting—pointofthebranch，butatthesametimeitisinacentralposition。Henceitiseitherthisthatiscutoff，orintothisthatthenewshootisinserted，whenwewisheitheranewbranchoranewroottospringfromit；whichprovesthatthepointoforiginingrowthisintermediatebetweenstemandroot。

Likewiseinsanguineousanimalstheheartisthefirstorgandeveloped；thisisevidentfromwhathasbeenobservedinthosecaseswhereobservationoftheirgrowthispossible。Henceinbloodlessanimalsalsowhatcorrespondstotheheartmustdevelopfirst。WehavealreadyassertedinourtreatiseonThePartsofAnimalsthatitisfromtheheartthattheveinsissue，andthatinsanguineousanimalsthebloodisthefinalnutrimentfromwhichthemembersareformed。Henceitisclearthatthereisonefunctioninnutritionwhichthemouthhasthefacultyofperforming，andadifferentoneappertainingtothestomach。Butitistheheartthathassupremecontrol，exercisinganadditionalandcompletingfunction。

Henceinsanguineousanimalsthesourcebothofthesensitiveandofthenutritivesoulmustbeintheheart，forthefunctionsrelativetonutritionexercisedbytheotherpartsareancillarytotheactivityoftheheart。Itisthepartofthedominatingorgantoachievethefinalresult，asofthephysician’seffortstobedirectedtowardshealth，andnottobeoccupiedwithsubordinateoffices。

Certainly，however，allsaguineousanimalshavethesupremeorganofthesensefacultiesintheheart，foritisherethatwemustlookforthecommonsensoriumbelongingtoallthesense—organs。Theseintwocases，tasteandtouch，canbeclearlyseentoextendtotheheart，andhencetheothersalsomustleadtoit，forinittheotherorgansmaypossiblyinitiatechanges，whereaswiththeupperregionofthebodytasteandtouchhavenoconnexion。Apartfromtheseconsiderations，ifthelifeisalwayslocatedinthispart，evidentlytheprincipleofsensationmustbesituatedtheretoo，foritisquaanimalthatananimalissaidtobealivingthing，anditiscalledanimalbecauseendowedwithsensation。Elsewhereinotherworkswehavestatedthereasonswhysomeofthesense—organsare，asisevident，connectedwiththeheart，whileothersaresituatedinthehead。（Itisthisfactthatcausessomepeopletothinkthatitisinvirtueofthebrainthatthefunctionofperceptionbelongstoanimals。）

4

Thusif，ontheonehand，welooktotheobservedfacts，whatwehavesaidmakesitclearthatthesourceofthesensitivesoul，togetherwiththatconnectedwithgrowthandnutrition，issituatedinthisorganandinthecentraloneofthethreedivisionsofthebody。Butitfollowsbydeductionalso；forweseethatineverycase，whenseveralresultsareopentoher，Naturealwaysbringstopassthebest。Nowifbothprinciplesarelocatedinthemidstofthesubstance，thetwopartsofthebody，viz。thatwhichelaboratesandthatwhichreceivesthenutrimentinitsfinalformwillbestperformtheirappropriatefunction；forthesoulwillthenbeclosetoeach，andthecentralsituationwhichitwill，assuch，occupyisthepositionofadominatingpower。

Further，thatwhichemploysaninstrumentandtheinstrumentitemploysmustbedistinct（andmustbespatiallydiversetoo，ifpossible，asincapacity），justasthefluteandthatwhichplaysit—thehand—arediverse。Thusifanimalisdefinedbythepossessionofsensitivesoul，thissoulmustinthesanguineousanimalsbeintheheart，and，inthebloodlessones，inthecorrespondingpartoftheirbody。Butinanimalsallthemembersandthewholebodypossesssomeconnatewarmthofconstitution，andhencewhenalivetheyareobservedtobewarm，butwhendeadanddeprivedoflifetheyaretheopposite。Indeed，thesourceofthiswarmthmustbeintheheartinsanguineousanimals，andinthecaseofbloodlessanimalsinthecorrespondingorgan，for，thoughallpartsofthebodybymeansoftheirnaturalheatelaborateandconcoctthenutriment，thegoverningorgantakesthechiefshareinthisprocess。Hence，thoughtheothermembersbecomecold，liferemains；butwhenthewarmthhereisquenched，deathalwaysensues，becausethesourceofheatinalltheothermembersdependsonthis，andthesoulis，asitwere，setaglowwithfireinthispart，whichinsanguineousanimalsistheheartandinthebloodlessordertheanalogousmember。Hence，ofnecessity，lifemustbecoincidentwiththemaintenanceofheat，andwhatwecalldeathisitsdestruction。

5

However，itistobenoticedthattherearetwowaysinwhichfireceasestoexist；itmaygoouteitherbyexhaustionorbyextinction。Thatwhichisself—causedwecallexhaustion，thatduetoitsoppositesextinction。[Theformeristhatduetooldage，thelattertoviolence。]Buteitherofthesewaysinwhichfireceasestobemaybebroughtaboutbythesamecause，for，whenthereisadeficiencyofnutrimentandthewarmthcanobtainnomaintenance，thefirefails；andthereasonisthattheopposite，checkingdigestion，preventsthefirefrombeingfed。Butinothercasestheresultisexhaustion，—whentheheataccumulatesexcessivelyowingtolackofrespirationandofrefrigeration。Forinthiscasewhathappensisthattheheat，accumulatingingreatquantity，quicklyusesupitsnutrimentandconsumesitallbeforemoreissentupbyevaporation。Hencenotonlyisasmallerfirereadilyputoutbyalargeone，butofitselfthecandleflameisconsumedwheninsertedinalargeblazejustasisthecasewithanyothercombustible。Thereasonisthatthenutrimentintheflameisseizedbythelargeronebeforefreshfuelcanbeadded，forfireisevercomingintobeingandrushingjustlikeariver，butsospeedilyastoeludeobservation。

Clearlytherefore，ifthebodilyheatmustbeconserved（asisnecessaryiflifeistocontinue），theremustbesomewayofcoolingtheheatresidentinthesourceofwarmth。Takeasanillustrationwhatoccurswhencoalsareconfinedinabrazier。Iftheyarekeptcoveredupcontinuouslybytheso—called’choker’，theyarequicklyextinguished，but，ifthelidisinrapidalternationliftedupandputonagaintheyremainglowingforalongtime。Bankingupafirealsokeepsitin，fortheashes，beingporous，donotpreventthepassageofair，andagaintheyenableittoresistextinctionbythesurroundingairbymeansofthesupplyofheatwhichitpossesses。

However，wehavestatedinTheProblemsthereasonswhytheseoperations，namelybankingupandcoveringupafire，havetheoppositeeffects（intheonecasethefiregoesout，intheotheritcontinuesaliveforaconsiderabletime）。

6

Everythinglivinghassoul，andit，aswehavesaid，cannotexistwithoutthepresenceofheatintheconstitution。Inplantsthenaturalheatissufficientlywellkeptalivebytheaidwhichtheirnutrimentandthesurroundingairsupply。Forthefoodhasacoolingeffect[asitenters，justasithasinman]whenfirstitistakenin，whereasabstinencefromfoodproducesheatandthirst。Theair，ifitbemotionless，becomeshot，butbytheentryoffoodamotionissetupwhichlastsuntildigestioniscompletedandsocoolsit。Ifthesurroundingairisexcessivelycoldowingtothetimeofyear，therebeingseverefrost，plantsshrivel，orif，intheextremeheatsofsummerthemoisturedrawnfromthegroundcannotproduceitscoolingeffect，theheatcomestoanendbyexhaustion。Treessufferingatsuchseasonsaresaidtobeblightedorstar—stricken。

Hencethepracticeoflayingbeneaththerootsstonesofcertainspeciesorwaterinpots，forthepurposeofcoolingtherootsoftheplants。

Someanimalspasstheirlifeinthewater，othersintheair，andthereforethesemediafurnishthesourceandmeansofrefrigeration，waterintheonecase，airintheother。Wemustproceed—anditwillrequirefurtherapplicationonourpart—togiveanaccountofthewayandmannerinwhichthisrefrigerationoccurs。

7

Afewofthepreviousphysicalphilosophershavespokenofrespiration。Thereason，however，whyitexistsinanimalstheyhaveeithernotdeclaredor，whentheyhave，theirstatementsarenotcorrectandshowacomparativelackofacquaintancewiththefacts。

Moreovertheyassertthatallanimalsrespire—whichisuntrue。Hencethesepointsmustfirstclaimourattention，inorderthatwemaynotbethoughttomakeunsubstantiatedchargesagainstauthorsnolongeralive。

Firstthen，itisevidentthatallanimalswithlungsbreathe，butinsomecasesbreathinganimalshaveabloodlessandspongylung，andthenthereislessneedforrespiration。Theseanimalscanremainunderwaterforatime，whichrelativelytotheirbodilystrength，isconsiderable。Alloviparousanimals，e。g。thefrog—tribe，haveaspongylung。Alsohemydesandtortoisescanremainforalongtimeimmersedinwater；fortheirlung，containinglittleblood，hasnotmuchheat。Hence，whenonceitisinflated，ititself，bymeansofitsmotion，producesacoolingeffectandenablestheanimaltoremainimmersedforalongtime。Suffocation，however，alwaysensuesiftheanimalisforcedtoholditsbreathfortoolongatime，fornoneofthisclasstakeinwaterinthewayfishesdo。Ontheotherhand，animalswhichhavethelungchargedwithbloodhavegreaterneedofrespirationonaccountoftheamountoftheirheat，whilenoneatalloftheotherswhichdonotpossesslungsbreathe。

8

DemocritusofAbderaandcertainotherswhohavetreatedofrespiration，whilesayingnothingdefiniteaboutthelunglessanimals，neverthelessseemtospeakasifallbreathed。ButAnaxagorasandDiogenesbothmaintainthatallbreathe，andstatethemannerinwhichfishesandoystersrespire。Anaxagorassaysthatwhenfishesdischargewaterthroughtheirgills，airisformedinthemouth，fortherecanbenovacuum，andthatitisbydrawinginthisthattheyrespire。

Diogenes’statementisthat，whentheydischargewaterthroughtheirgills，theysucktheairoutofthewatersurroundingthemouthbymeansofthevacuumformedinthemouth，forhebelievesthereisairinthewater。

Butthesetheoriesareuntenable。Firstly，theystateonlywhatisthecommonelementinbothoperationsandsoleaveoutthehalfofthematter。Forwhatgoesbythenameofrespirationconsists，ontheonehand，ofinhalation，and，ontheother，oftheexhalationofbreath；but，aboutthelattertheysaynothing，nordotheydescribehowsuchanimalsemittheirbreath。Indeed，explanationisforthemimpossiblefor，whenthecreaturesrespire，theymustdischargetheirbreathbythesamepassageasthatbywhichtheydrawitin，andthismusthappeninalternation。Hence，asaresult，theymusttakethewaterintotheirmouthatthesametimeastheybreatheout。Buttheairandthewatermustmeetandobstructeachother。Further，whentheydischargethewatertheymustemittheirbreathbythemouthorthegills，andtheresultwillbethattheywillbreatheinandbreatheoutatthesametime，foritisatthatmomentthatrespirationissaidtooccur。Butitisimpossiblethattheyshoulddobothatthesametime。Hence，ifrespiringcreaturesmustbothexhaleandinhaletheair，andifnoneoftheseanimalscanbreatheout，evidentlynonecanrespireatall。

9

Further，theassertionthattheydrawinairoutofthemouthoroutofthewaterbymeansofthemouthisanimpossibility，for，nothavingalung，theyhavenowindpipe；ratherthestomachiscloselyjuxtaposedtothemouth，sothattheymustdothesuckingwiththestomach。Butinthatcasetheotheranimalswoulddosoalso，whichisnotthetruth；andthewater—animalsalsowouldbeseentodoitwhenoutofthewater，whereasquiteevidentlytheydonot。Further，inallanimalsthatrespireanddrawbreaththereistobeobservedacertainmotioninthepartofthebodywhichdrawsintheair，butinthefishesthisdoesnotoccur。Fishesdonotappeartomoveanyofthepartsintheregionofthestomach，exceptthegillsalone，andthesemovebothwhentheyareinthewaterandwhentheyarethrownontodrylandandgasp。Moreover，alwayswhenrespiringanimalsarekilledbybeingsuffocatedinwater，bubblesareformedoftheairwhichisforciblydischarged，ashappens，e。g。whenoneforcesatortoiseorafrogoranyotheranimalofasimilarclasstostaybeneathwater。Butwithfishesthisresultneveroccurs，inwhatsoeverwaywetrytoobtainit，sincetheydonotcontainairdrawnfromanexternalsource。Again，themannerofrespirationsaidtoexistinthemmightoccurinthecaseofmenalsowhentheyareunderwater。

Foriffishesdrawinairoutofthesurroundingwaterbymeansoftheirmouthwhyshouldnotmentooandotheranimalsdosoalso；

theyshouldalso，inthesamewayasfishes，drawinairoutofthemouth。Ifintheformercaseitwerepossible，soalsoshoulditbeinthelatter。But，sinceintheoneitisnotso，neitherdoesitoccurintheother。Furthermore，whydofishes，iftheyrespire，dieintheairandgasp（ascanbeseen）asinsuffocation？Itisnotwantoffoodthatproducesthiseffectuponthem，andthereasongivenbyDiogenesisfoolish，forhesaysthatinairtheytakeintoomuchairandhencedie，butinthewatertheytakeinamoderateamount。Butthatshouldbeapossibleoccurrencewithlandanimalsalso；asfactsare，however，nolandanimalseemstobesuffocatedbyexcessiverespiration。Again，ifallanimalsbreathe，insectsmustdosoalso。

manyofthemseemtolivethoughdividednotmerelyintotwo，butintoseveralparts，e。g。theclasscalledScolopendra。Buthowcanthey，whenthusdivided，breathe，andwhatistheorgantheyemploy？Themainreasonwhythesewritershavenotgivenagoodaccountofthesefactsisthattheyhavenoacquaintancewiththeinternalorgans，andthattheydidnotacceptthedoctrinethatthereisafinalcauseforwhateverNaturedoes。Iftheyhadaskedforwhatpurposerespirationexistsinanimals，andhadconsideredthiswithreferencetotheorgans，e。g。thegillsandthelungs，theywouldhavediscoveredthereasonmorespeedily。

10

Democritus，however，doesteachthatinthebreathinganimalsthereisacertainresultproducedbyrespiration；heassertsthatitpreventsthesoulfrombeingextrudedfromthebody。

Nevertheless，hebynomeansassertsthatitisforthispurposethatNaturesocontrivesit，forhe，liketheotherphysicalphilosophers，altogetherfailstoattaintoanysuchexplanation。

Hisstatementisthatthesoulandthehotelementareidentical，beingtheprimaryformsamongthesphericalparticles。Hence，whenthesearebeingcrushedtogetherbythesurroundingatmospherethrustingthemout，respiration，accordingtohisaccount，comesintosuccourthem。Forintheairtherearemanyofthoseparticleswhichhecallsmindandsoul。Hence，whenwebreatheandtheairenters，theseenteralongwithit，andbytheiractioncancelthepressure，thuspreventingtheexpulsionofthesoulwhichresidesintheanimal。

Thisexplainswhylifeanddeathareboundupwiththetakinginandlettingoutofthebreath；fordeathoccurswhenthecompressionbythesurroundingairgainstheupperhand，and，theanimalbeingunabletorespire，theairfromoutsidecannolongerenterandcounteractthecompression。Deathisthedepartureofthoseformsowingtotheexpulsivepressureexertedbythesurroundingair。Death，however，occursnotbyhaphazardbut，whennatural，owingtooldage，and，whenunnatural，toviolence。

ButthereasonforthisandwhyallmustdieDemocritushasbynomeansmadeclear。Andyet，sinceevidentlydeathoccursatonetimeoflifeandnotatanother，heshouldhavesaidwhetherthecauseisexternalorinternal。Neitherdoesheassignthecauseofthebeginningofrespiration，norsaywhetheritisinternalorexternal。Indeed，itisnotthecasethattheexternalmindsuperintendsthereinforcement；rathertheoriginofbreathingandoftherespiratorymotionmustbewithin：itisnotduetopressurefromaround。Itisabsurdalsothatwhatsurroundsshouldcompressandatthesametimebyenteringdilate。Thisthenispracticallyhistheory，andhowheputsit。

Butifwemustconsiderthatourpreviousaccountistrue，andthatrespirationdoesnotoccurineveryanimal，wemustdeemthatthisexplainsdeathnotuniversally，butonlyinrespiringanimals。

Yetneitherisitagoodaccountoftheseeven，asmayclearlybeseenfromthefactsandphenomenaofwhichweallhaveexperience。Forinhotweatherwegrowwarmer，and，havingmoreneedofrespiration，wealwaysbreathefaster。But，whentheairaroundiscoldandcontractsandsolidifiesthebody，retardationofthebreathingresults。Yetthiswasjustthetimewhentheexternalairshouldenterandannultheexpulsivemovement，whereasitistheoppositethatoccurs。Forwhenthebreathisnotletoutandtheheataccumulatestoomuchthenweneedtorespire，andtorespirewemustdrawinthebreath。Whenhot，peoplebreatherapidly，becausetheymustdosoinordertocoolthemselves，justwhenthetheoryofDemocrituswouldmakethemaddfiretofire。

11

ThetheoryfoundintheTimaeus，ofthepassingroundofthebreathbypushing，bynomeansdetermineshow，inthecaseoftheanimalsotherthanland—animals，theirheatispreserved，andwhetheritisduetothesameoradifferentcause。Forifrespirationoccursonlyinland—animalsweshouldbetoldwhatisthereasonofthat。Likewise，ifitisfoundinothersalso，butinadifferentform，thisformofrespiration，iftheyallcanbreathe，mustalsobedescribed。

Further，themethodofexplaininginvolvesafiction。Itissaidthatwhenthehotairissuesfromthemouthitpushesthesurroundingair，whichbeingcarriedonenterstheveryplacewhencetheinternalwarmthissued，throughtheintersticesoftheporousflesh；andthisreciprocalreplacementisduetothefactthatavacuumcannotexist。Butwhenithasbecomehottheairpassesoutagainbythesameroute，andpushesbackinwardsthroughthemouththeairthathadbeendischargedinawarmcondition。Itissaidthatitisthisactionwhichgoesoncontinuouslywhenthebreathistakeninandletout。

Butaccordingtothiswayofthinkingitwillfollowthatwebreatheoutbeforewebreathein。Buttheoppositeisthecase，asevidenceshows，forthoughthesetwofunctionsgooninalternation，yetthelastactwhenlifecomestoacloseisthelettingoutofthebreath，andhenceitsadmissionmusthavebeenthebeginningoftheprocess。

Oncemore，thosewhogivethiskindofexplanationbynomeansstatethefinalcauseofthepresenceinanimalsofthisfunction（towittheadmissionandemissionofthebreath），buttreatitasthoughitwereacontingentaccompanimentoflife。Yetitevidentlyhascontroloverlifeanddeath，foritresultssynchronouslythatwhenrespiringanimalsareunabletobreathetheyperish。Again，itisabsurdthatthepassageofthehotairoutthroughthemouthandbackagainshouldbequiteperceptible，whilewewerenotabletodetectthethoracicinfluxandthereturnoutwardsoncemoreoftheheatedbreath。Itisalsononsensethatrespirationshouldconsistintheentranceofheat，fortheevidenceistothecontraryeffect；

whatisbreathedoutishot，andwhatisbreathediniscold。Whenitishotwepantinbreathing，for，becausewhatentersdoesnotadequatelyperformitscoolingfunction，wehaveasaconsequencetodrawthebreathfrequently。

12

Itiscertain，however，thatwemustnotentertainthenotionthatitisforpurposesofnutritionthatrespirationisdesigned，andbelievethattheinternalfireisfedbythebreath；respiration，asitwere，addingfueltothefire，whilethefeedingoftheflameresultsintheoutwardpassageofthebreath。TocombatthisdoctrineIshallrepeatwhatIsaidinoppositiontotheprevioustheories。This，orsomethinganalogoustoit，shouldoccurintheotheranimalsalso（onthistheory），forallpossessvitalheat。

Further，howarewetodescribethisfictitiousprocessofthegenerationofheatfromthebreath？Observationshowsratherthatitisaproductofthefood。Aconsequencealsoofthistheoryisthatthenutrimentwouldenterandtherefusebedischargedbythesamechannel，butthisdoesnotappeartooccurintheotherinstances。

13

Empedoclesalsogivesanaccountofrespirationwithout，however，makingclearwhatitspurposeis，orwhetherornotitisuniversalinanimals。Alsowhendealingwithrespirationbymeansofthenostrilsheimaginesheisdealingwithwhatistheprimarykindofrespiration。Eventhebreathwhichpassesthroughthenostrilspassesthroughthewindpipeoutofthechestaswell，andwithoutthelatterthenostrilscannotact。Again，whenanimalsarebereftofrespirationthroughthenostrils，nodetrimentalresultensues，but，whenpreventedfrombreathingthroughthewindpipe，theydie。

Natureemploysrespirationthroughthenostrilsasasecondaryfunctionincertainanimalsinordertoenablethemtosmell。Butthereasonwhyitexistsinsomeonlyisthatthoughalmostallanimalsareendowedwiththesenseofsmell，thesense—organisnotthesameinall。

Amorepreciseaccounthasbeengivenaboutthiselsewhere。

Empedocles，however，explainsthepassageinwardsandoutwardsofthebreath，bythetheorythattherearecertainblood—vessels，which，whilecontainingblood，arenotfilledbyit，buthavepassagesleadingtotheouterair，thecalibreofwhichisfineincontrasttothesizeofthesolidparticles，butlargerelativelytothoseintheair。Hence，sinceitisthenatureofthebloodtomoveupwardsanddownwards，whenitmovesdowntheairrushesinandinspirationoccurs；whenthebloodrises，theairisforcedoutandtheoutwardmotionofthebreathresults。Hecomparesthisprocesstowhatoccursinaclepsydra。

Thusallthingsoutwardsbreatheandin；—theirfleshhastubesBloodless，thatstretchtowardsthebody’soutmostedge，Which，attheirmouths，fullmanyfrequentchannelspierce，Cleavingtheextremenostrilsthrough；thus，whilethegoreLieshid，forairiscutathoroughfaremostplain。

Andthence，whenevershrinksawaythetenderblood，Enterstheblusteringwindwithswellingbillowwild。

Butwhenthebloodleapsup，backwarditbreathes。AswhenWithwater—clockofpolishedbronzeamaidensporting，SetsonhercomelyhandthenarrowofthetubeAnddipsitinthefrail—formedwater’ssilverysheen；

Notthenthefloodthevesselenters，buttheair，Untilshefreesthecrowdedstream。ButthenindeedUpontheescaperunsinthewatermeet。

Soalsowhenwithinthevessel’sdeepsthewaterRemains，theopeningbythehandoffleshbeingclosed，TheouterairthatentrancecravesrestrainsthefloodAtthegatesofthesoundingnarrow，uponthesurfacepressing，Untilthemaidwithdrawsherhand。ButthenincontrariwiseOncemoretheaircomesinandwatermeetflowsout。

Thustothetothesubtleblood，surgingthroughoutthelimbs，Whene’eritshrinksawayintothefarrecessesAdmitsastreamofairrushingwithswellingwave，But，whenitbackwardleaps，inlikebulkairflowsout。