§ 54. Personal liability of heads of agencies. No head of any agency, department, bureau, or office of a county shall be liable to respond in damages to the county or to any other person for any act or omission of any employee of the county employed within the agency, department, bureau, or office of which he is such head. Any lawful claims which but for this section would be claims against such head of an agency, department, bureau, or office shall be lawful claims against the county and shall be deemed to be the liability of the county. Nothing contained herein, however, shall be deemed to relieve the head of any agency, department, bureau, or office of liability to the county or to any other person for his own act or omission to act, nor be deemed to impose any new liability upon the county for any act or omission of such head of any agency, department, bureau, or office to which the county was not lawfully subject prior to the taking effect of this act.