The Lunacy Act 1890 (53 Vict. ch. 5) formed the basis of mental health law in England and Wales from 1890 until 1959.
You can find the main provisions of the Act here.
It placed an obligation on local authorities to maintain institutions for the mentally ill.
The Lunacy Act 1845 and the County Asylums Act 1845 were later repealed by the Lunacy Act 1890 which made small changes, and the Lunacy Commission were handed more powers and renamed the “Board of Control” in the Mental Deficiency Act 1913.
The Board of Control would later be altered in the Mental Health Act 1930 and the National Health Service Act 1946.