son ▁A ck man ▁( born ▁ 1 9 9 3 ), ▁Canadian ▁sw immer ▁ ▁Amy ▁V era ▁A ck man , ▁also ▁known ▁as ▁Mother ▁Giovanni ▁( 1 8 8 6 – 1 9 6 6 ), ▁Australian ▁hospital ▁administrator ▁ ▁Bill ▁A ck man , ▁American ▁h edge ▁fund ▁manager ▁ ▁Dan ▁A ck man , ▁American ▁journalist ▁and ▁civil ▁rights ▁lawyer ▁ ▁Margaret ▁A ck man , ▁Gu yan ese ▁politician ▁ ▁Robert ▁A ck man ▁( 1 9 2 7 – 2 0 1 3 ), ▁Canadian ▁chem istry ▁professor <0x0A> </s> ▁St ann ius ▁Lig ature ▁is ▁an ▁experimental ▁procedure ▁to ▁illustrate ▁imp ulse ▁condu ction ▁in ▁f rog ▁heart . ▁A ▁lig ature ▁placed ▁either ▁around ▁the ▁j unction ▁between ▁the ▁sin us ▁ven os us ▁and ▁at rium ▁of ▁the ▁f rog ▁or ▁t urt le ▁heart ▁( first ▁st ann ius ▁lig ature ) ▁or ▁around ▁the ▁at ri ov ent ric ular ▁j unction ▁( second ▁st ann ius ▁lig ature ); ▁demonstr ates ▁that ▁the ▁card iac ▁imp ulse ▁is ▁conducted ▁from ▁sin us ▁ven os us ▁to ▁at ria ▁to ▁vent ric le , ▁but ▁that ▁success ive ▁ch amb ers ▁possess ▁automatic ity ▁since ▁each ▁may ▁continue ▁to ▁beat , ▁but ▁the ▁at ria ▁now ▁have ▁a ▁slower ▁rate ▁than ▁the ▁sin us ▁ven os us , ▁and ▁the ▁vent ric le ▁either ▁does ▁not ▁contract ▁or ▁be ats ▁at ▁a ▁slower ▁rate ▁than ▁the ▁at ria . ▁ ▁History