Immediately upon the transfer of the property of any State hospital as hereinbefore provided, there shall be appointed to manage such hospital a board of nine trustees, three to be appointed by the Governor and six by the incorporated hospital association. Of the trustees first appointed by the Governor, one shall serve for one year, one for two years, one for three years, and, upon the expiration of the respective periods and thereafter, the vacancy shall be filled by the Governor for a term of three years. Of the trustees appointed by the incorporated hospital association, two shall serve for one year, two for two years, two for three years, and, upon the expiration of the respective periods, vacancies shall be filled by the incorporated hospital association for a term of three years. Should any vacancy occur by the death, resignation, or incapacity of any trustees, such vacancy shall be filled by appointment for the unexpired term of such trustee. The board of trustees shall manage and direct the affairs of such hospital, and make all necessary by-laws and regulations not inconsistent with the Constitution and laws of the Commonwealth.