The governing authority may appropriate and pay into the fund out of the annual revenues of the municipality a sum not to exceed the equivalent of one mill on the dollar of assessed valuation of all property in the municipality.  This amount from the general revenues shall be discontinued by the municipal government whenever the interest from the fund is sufficient to pay all disability and relief benefits which are charged against the fund.  When the interest from the fund becomes insufficient to meet the charges of disability and relief the municipal government may reinstate the amount from the general revenues for the purpose of building up the fund until the interest is sufficient to pay the obligations of the fund.