Each police matron shall be (1) a female police officer or (2) a woman at least eighteen years of age. The hiring authority may establish other qualifications for the employment of police matrons and require evidence of fulfillment of these qualifications. Such matron shall receive such salary as the common council of the city determines and may be removed by the board of police commissioners or police committee if, in its judgment, the public interest requires it. The officer in charge of the station shall, whenever it is necessary, order policemen to assist the matron upon her request for such assistance.