Appropriations for assistance under this chapter when used in programs entitled to receive federal matching funds shall not lapse but shall be a continuing account so long and as federal grants are available to match the State's contribution. No payments matchable by federal funds shall be made out of said account if federal grants or state appropriations are withdrawn, except that medical or remedial care or services contracted for before the date of such withdrawal shall be paid. Any money left in said fund in the event of withdrawal of federal grants or state appropriations shall be divided between the State and the Federal Government in proportion to the amount contributed by each.   [PL 1973, c. 790, §2 (NEW).]