After the establishment of a county welfare-house as provided in section 44:4-4 of this title, the permanent poor shall be maintained therein in lieu of almshouses, and almshouses maintained and supported in any such county or in municipalities in such county shall be abolished; except where a municipality of such county maintains an institution suitable and adequate for the care and maintenance of the permanent poor of the county, and upon the approval of the department of institutions and agencies as to suitability and adequacy and cost of maintenance of the permanent poor to be provided therein, the county shall thereupon enter into contract with such municipality for the care and maintenance of its permanent poor.