Sections 21-37-33 through 21-37-39 shall be liberally construed to promote the efficient maintenance and operation of such parks, playgrounds, and swimming pools to the end that it may result in the improvement of the general health, entertainment and happiness of the citizens of such municipalities. Such sections shall not be compulsory on any municipality, but the governing authorities of any municipality may come under said sections by adopting an ordinance, duly spread on their minutes determining to do so.