Mass. Gen. Laws ch. 112, § 12Z

Every physician attending or treating a case of dog bite or whenever any such case is treated in a hospital, sanatorium or other institution, the manager, superintendent or other person in charge thereof, shall report such case within twenty-four hours to the inspector of animals of the city or town where such dog bite occurred; provided, however, that if such city or town does not have an inspector of animals said report shall be made to the dog officer.