The governing body in all counties of the first class having a charter form of government, in addition to the power to levy taxes for county purposes as otherwise provided by law, shall have the power to levy upon all real and tangible personal property in the county an annual tax in an amount not to exceed thirty-eight cents on each one hundred dollars valuation for the purpose of operating, maintaining or supporting a public county hospital or public hospital system or for the maintenance of county patients in state institutions, public hospitals, or other hospitals and for the purpose of operating or maintaining a public county health center or institution and conducting public health programs. The proceeds of the tax shall be used for such purposes and for no other purposes, and no funds from the general revenue of the county shall hereafter be appropriated for such purposes.