Subject to the provisions of this act each such board of trustees shall operate the hospital or institution under its charge and may employ, within appropriations made by the board of supervisors of the county, a medical superintendent, physicians, nurses, and such other employees as may be necessary. The medical staff of the hospital shall with the approval of the board of trustees adopt rules, regulations and policies governing the professional work of the hospital and the eligibility and qualifications of its medical staff, which may conform, as nearly as practicable, to the applicable standards recommended by the American College of Surgeons. Money to defray the expenses of maintenance and operation subject to audit as in section 8 provided shall be paid by the county treasurer having such funds in its custody on the warrant of the president of the board of trustees of the hospital, countersigned by the secretary.