Thistheniswhathesaysofrespiration。But，aswesaid，allanimalsthatevidentlyrespiredosobymeansofthewindpipe，whentheybreatheeitherthroughthemouthorthroughthenostrils。
Hence，ifitisofthiskindofrespirationthatheistalking，wemustaskhowittallieswiththeexplanationgiven。Butthefactsseemtobequiteopposed。Thechestisraisedinthemannerofaforge—bellowswhenthebreathisdrawnin—itisquitereasonablethatitshouldbeheatwhichraisesupandthatthebloodshouldoccupythehotregion—butitcollapsesandsinksdown，likethebellowsoncemore，whenthebreathisletout。Thedifferenceisthatinabellowsitisnotbythesamechannelthattheairistakeninandletout，butinbreathingitis。
But，ifEmpedoclesisaccountingonlyforrespirationthroughthenostrils，heismuchinerror，forthatdoesnotinvolvethenostrilsalone，butpassesbythechannelbesidetheuvulawheretheextremityoftheroofofthemouthis，someoftheairgoingthiswaythroughtheaperturesofthenostrilsandsomethroughthemouth，bothwhenitentersandwhenitpassesout。Suchthenisthenatureandmagnitudeofthedifficultiesbesettingthetheoriesofotherwritersconcerningrespiration。
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Wehavealreadystatedthatlifeandthepresenceofsoulinvolveacertainheat。Noteventhedigestingprocesstowhichisduethenutritionofanimalsoccursapartfromsoulandwarmth，foritistofirethatinallcaseselaborationisdue。Itisforthisreason，precisely，thattheprimarynutritivesoulalsomustbelocatedinthatpartofthebodyandinthatdivisionofthisregionwhichistheimmediatevehicleofthisprinciple。Theregioninquestionisintermediatebetweenthatwherefoodentersandthatwhereexcrementisdischarged。Inbloodlessanimalsithasnoname，butinthesanguineousclassthisorganiscalledtheheart。Thebloodconstitutesthenutrimentfromwhichtheorgansoftheanimalaredirectlyformed。Likewisethebloodvesselsmusthavethesameoriginatingsource，sincetheoneexistsfortheother’sbehoof—asavesselorreceptacleforit。Insanguineousanimalstheheartisthestarting—pointoftheveins；theydonottraverseit，butarefoundtostretchoutfromit，asdissectionsenableustosee。