For the purpose of providing assistance for permanently totally disabled needy people under the age of (sixty-five) 65 years and over the age of (eighteen) 18 years who are unable to work, a statewide system of assistance is hereby established and shall be in effect in all political subdivisions of the state, to operate with due regard to varying conditions and cost of living, to be financed by state appropriations therefor, and to be administered by the state department of public welfare, as hereinafter provided.