Except as herein provided, members of the system shall have and possess no claim or recourse against any of the funds of the municipality by virtue of the adoption or operation of any plan for rendering medical care, indemnifying costs of said care or carrying insurance against such costs, but except as herein provided, the claim and recourse of any such member shall be limited solely to the funds of the system. All expenses of the system shall be paid exclusively from the health service system fund, and, except as herein provided, the City and County and the San Francisco Unified School District shall not appropriate or contribute funds in any manner for the purposes of the system hereby established and provided.