Municipal authorities, by ordinance, in all cities of the first class in this state, having an organized police department, or having an organized fire department, may provide for a pension fund for the pensioning of retired, crippled or disabled members of such police department or such fire department, and the dependent widow and minor children of deceased members, and such cities may appropriate or set apart from special or general municipal funds such percent or amount as may be fixed by the ordinance therefor, subject to existing constitutional or statutory limitations, said fund to be managed by a board of trustees, and the treasurer of said city shall be the treasurer of said funds.