▁these ▁curves ▁has ▁a ▁Jacob ian ▁variety ▁J C t ▁( if ▁a ▁curve ▁is ▁singular , ▁there ▁is ▁an ▁appropriate ▁generalized ▁Jacob ian ▁variety ). ▁These ▁can ▁be ▁assemble d ▁into ▁a ▁family ▁, ▁the ▁Jacob ian ▁of ▁the ▁p enc il , ▁which ▁comes ▁with ▁a ▁projection ▁map ▁ π ▁to ▁the ▁base ▁T ▁of ▁the ▁p enc il . ▁A ▁normal ▁function ▁is ▁a ▁( hol omorphic ) ▁section ▁of ▁ π . ▁ ▁Fix ▁an ▁embedding ▁of ▁X ▁in ▁P N , ▁and ▁choose ▁a ▁p enc il ▁of ▁curves ▁C t ▁on ▁X . ▁ ▁For ▁a ▁fixed ▁curve ▁ Γ ▁on ▁X , ▁the ▁intersection ▁of ▁ Γ ▁and ▁C t ▁is ▁a ▁divis or ▁ ▁on ▁C t , ▁where ▁d ▁is ▁the ▁degree ▁of ▁X . ▁Fix ▁a ▁base ▁point ▁p 0 ▁of ▁the ▁p enc il . ▁ ▁Then ▁the ▁divis or ▁ ▁is ▁a ▁divis or ▁of ▁degree ▁zero , ▁and ▁consequ ently ▁it ▁determ ines ▁a ▁class ▁ ν Γ ( t ) ▁in ▁the ▁Jacob ian ▁J C t ▁for ▁all ▁t . ▁The ▁map ▁from ▁t ▁to ▁ ν Γ ( t ) ▁is ▁a ▁normal ▁function . ▁▁ ▁Henri ▁Po inc ar é ▁proved ▁that ▁for ▁a ▁general ▁p enc il ▁of ▁curves , ▁all ▁normal ▁functions ▁arose ▁as ▁ ν Γ ( t ) ▁for ▁some ▁choice ▁of ▁ Γ . ▁Le f sch etz ▁proved ▁that ▁any ▁normal ▁function ▁determined ▁a ▁class ▁in ▁H 2 ( X