Section 13A. A society, except one organized under section 46, whose rates and benefits are approved by the commissioner, may set up and provide under its by-laws a plan for the payment of hospital and medical expenses and for the services of surgeons, physicians and nurses, or for any one of these services or expenses, in connection with sickness, disease or accidents, or the results therefrom. The by-laws shall also provide that an independent hospitalization and medical service fund be created and maintained, with the accretions thereto, separate and apart from other funds of the society; that no benefits of any kind shall be paid until there is accumulated in the fund an amount not less than that received from three monthly contributions or one quarterly contribution, and that this amount shall be the minimum of surplus below which additional contributions from members shall be required; that there shall be included in the liabilities of the fund reserves for unearned assessments and unpaid claims; and that no benefits shall be paid on any claim for a period exceeding one year.