1. All mentally ill, developmentally disabled, blind and deaf and mute persons, the expense of whose support and maintenance now is, or, under the laws of the state of New York, may become a charge upon the city of Poughkeepsie, or the county of Dutchess, exclusive of said city, or both, and who are maintained, or shall be maintained, in any of the institutions of the state of New York, shall be supported by said county of Dutchess as one district.
2. All institutions in the state of New York maintaining any such person whose support is properly chargeable, or shall be properly chargeable, to said city or county, are hereby required to render to the county treasurer of said county all bills for the support of such persons without any distinction between those persons from the different parts of said county.
3. This section shall not be held to affect chapter two hundred and eighty-six of the laws of eighteen hundred and sixty-three, an act for the better support of the poor in the city of Poughkeepsie, except as to the class of persons herein named.