Section 3. Persons desiring to form a medical service corporation shall incorporate as provided in section three of chapter one hundred and eighty. Every certificate of organization of a medical service corporation formed under this chapter, before being filed under chapter one hundred and eighty, shall have endorsed thereon or attached thereto the consent of the department of public health and of the commissioner of public welfare. The board of directors of a medical service corporation shall number not less than nine, of whom at least three and not more than one third shall be subscribing members of such a medical service corporation and of whom at least three and not more than one third shall be physicians who are members of the Massachusetts Medical Society or other recognized association of physicians and who are not associated physicians of the medical service plan.