§ 939. Medical assistants in counties of New York and Kings. The district attorneys of the county of New York and of the county of Kings are each authorized and empowered to appoint and at pleasure to remove a medical assistant, who shall be a physician and surgeon, resident of the county in which he is appointed, and who shall have been for at least ten years duly licensed to practice medicine in this state. It shall be the duty of such medical assistant, under the supervision and direction of the district attorney, to examine into and report on all cases of suspicious, sudden and unusual death and wounding within the county, and to perform such duties as the district attorney may direct in connection with the official duties of such district attorney in the enforcement and administration of the criminal laws. Such medical assistant shall have the power and authority, whenever so directed by the district attorney, to dissect, perform an autopsy upon, or attend an autopsy upon any dead body of a human being. The salaries of the medical assistants of the county of New York and of the county of Kings shall be fixed and determined by the district attorney of New York county and the board of estimate, respectively, and shall be county charges.