Section 19. A woman shall not be appointed a police matron unless she is suitable therefor and has been recommended in writing by at least ten women of good standing, residents of the city where the appointment is to be made. The two preceding sentences shall not apply to police matrons in cities having more than thirty thousand inhabitants. A police matron may be removed by the mayor or police commissioner, as the case may be, by written order stating the cause of removal. Upon her death, resignation or removal her successor shall be appointed as soon as may be. She shall receive a reasonable compensation, which shall be fixed, except in Boston, by the city council, and in Boston, by the concurrent action of the city council and of the police commissioner, and shall be paid by the city treasurer upon the requisition of the body fixing her compensation. If only one police matron is attached to a station, she shall reside within a reasonable distance thereof and shall be ready to respond to a call therefrom at any hour of the day or night. If two police matrons are attached to a station, the hours during which they shall respond to calls therefrom, respectively, shall be so fixed by the mayor or police commissioner that one of them shall be ready to respond at any hour of the day and night, and each such matron shall, during the hours so fixed for her, remain within a reasonable distance of such station and be ready to respond to any call therefrom. One of such matrons shall remain constantly at the police station to which she is attached, ready for service, so long as any female is detained, lodged or held under arrest therein. A police matron shall have the entire care and charge of all females held under arrest, detained or lodged in the station to which she is attached, and she may call upon the officer in command of such station for assistance. She shall be subject to the authority of the head of the police department of the city where she serves, and to the rules and regulations, consistent with sections eighteen to twenty, inclusive, which may be prescribed by such authority; but she shall not be subject to the control or direction of any police officer attached to a station except the officer in command thereof at the time. In every station to which a police matron is attached, the mayor or police commissioner shall, at the expense of the city, provide sufficient and proper accommodation for females held under arrest, detained or lodged therein.