▁the ▁conclusion ▁that ▁n erves ▁were ▁not ▁h ollow . ▁ ▁Ab dom inal ▁org ans ▁▁▁ ▁In ▁De ▁fab rica , ▁he ▁corrected ▁an ▁earlier ▁claim ▁he ▁made ▁in ▁Tab ula e ▁about ▁the ▁right ▁kid ney ▁being ▁set ▁higher ▁than ▁the ▁left . ▁ ▁V es al ius ▁claimed ▁that ▁the ▁kid ne ys ▁were ▁not ▁a ▁filter ▁device ▁for ▁ur ine ▁to ▁pass ▁through , ▁but ▁rather ▁that ▁the ▁kid ne ys ▁serve ▁to ▁filter ▁blood ▁as ▁well , ▁and ▁that ▁ex cret ions ▁from ▁the ▁kid ne ys ▁travel led ▁through ▁the ▁u re ters ▁to ▁the ▁bl ad der . ▁ ▁He ▁described ▁the ▁o ment um , ▁and ▁its ▁connections ▁with ▁the ▁st om ach , ▁the ▁s ple en ▁and ▁the ▁colon ▁gave ▁the ▁first ▁correct ▁views ▁of ▁the ▁structure ▁of ▁the ▁p yl orus . ▁ ▁He ▁also ▁observed ▁the ▁small ▁size ▁of ▁the ▁ca ec al ▁append ix ▁in ▁man ▁and ▁gave ▁the ▁first ▁good ▁account ▁of ▁the ▁medi ast in um ▁and ▁ple ura . ▁ ▁V es al ius ▁admitted ▁that ▁due ▁to ▁a ▁lack ▁of ▁pre gn ant ▁cada vers ▁he ▁was ▁unable ▁to ▁come ▁to ▁a ▁significant ▁understanding ▁of ▁the ▁re product ive ▁org ans . ▁ ▁However , ▁he ▁did ▁find ▁that ▁the ▁u ter us ▁had ▁been ▁f als ely ▁identified ▁as ▁having ▁two ▁distinct ▁sections . ▁ ▁Heart ▁▁▁ ▁Through ▁his ▁work ▁with ▁mus cles , ▁V es al ius ▁believed ▁that ▁a ▁criter ion ▁for ▁mus