Every medical service corporation shall issue to its members certificates of membership which shall set forth the contract between the medical service corporation and the member and specify how the holder of the contract may obtain the names and addresses of the physicians upon whom the member shall have the right to call for medical services and the nature of such services. The certificate shall be consistent with this chapter and the purposes of this chapter. It shall contain no unnecessary or rigid restriction, limitation, or exclusion. It shall be prepared with the greatest possible degree of clearness and in such a way as not to mislead the holder. The form, size of type, general arrangement, and contents of the certificate shall be subject to the approval of the Commissioner and the certificate shall be filed with and approved by him before being issued in this state.