en , ▁followed ▁by ▁an ▁animal ▁dis section ▁by ▁a ▁bar ber – sur geon ▁whose ▁work ▁was ▁directed ▁by ▁the ▁lect urer . ▁No ▁attempt ▁was ▁made ▁to ▁confirm ▁Gal en ' s ▁claims , ▁which ▁were ▁considered ▁un ass ailable . ▁V es al ius , ▁in ▁contrast , ▁performed ▁dis section ▁as ▁the ▁primary ▁teaching ▁tool , ▁handling ▁the ▁actual ▁work ▁himself ▁and ▁ur ging ▁students ▁to ▁perform ▁dis section ▁themselves . ▁He ▁considered ▁hands - on ▁direct ▁observation ▁to ▁be ▁the ▁only ▁reliable ▁resource . ▁ ▁V es al ius ▁created ▁detailed ▁illustr ations ▁of ▁an atom y ▁for ▁students ▁in ▁the ▁form ▁of ▁six ▁large ▁wood cut ▁post ers . ▁When ▁he ▁found ▁that ▁some ▁of ▁them ▁were ▁being ▁widely ▁copied , ▁he ▁published ▁them ▁all ▁in ▁ 1 5 3 8 ▁under ▁the ▁title ▁Tab ula e ▁an atom ica e ▁sex . ▁He ▁followed ▁this ▁in ▁ 1 5 3 9 ▁with ▁an ▁updated ▁version ▁of ▁Winter ' s ▁an atom ical ▁hand book , ▁Institution es ▁an atom ica e . ▁ ▁In ▁ 1 5 3 9 ▁he ▁also ▁published ▁his ▁Ven ese ction ▁letter ▁on ▁blood lett ing . ▁This ▁was ▁a ▁popular ▁treatment ▁for ▁almost ▁any ▁ill ness , ▁but ▁there ▁was ▁some ▁debate ▁about ▁where ▁to ▁take ▁the ▁blood ▁from . ▁The ▁classical ▁Greek ▁procedure , ▁advoc ated ▁by ▁Gal en , ▁was ▁to ▁collect ▁blood ▁from ▁a ▁site ▁near ▁the ▁location ▁of ▁the ▁ill ness . ▁However , ▁the ▁Muslim