For the purpose of this subtitle, the following classes of persons shall be deemed to be engaged in the practice of medicine and surgery or osteopathic medicine and surgery:
 1. Persons who publicly profess to be physicians and surgeons or osteopathic physicians and surgeons, or who publicly profess to assume the duties incident to the practice of medicine and surgery or osteopathic medicine and surgery.
 2. Persons who prescribe, or prescribe and furnish, medicine for human ailments or treat the same by surgery.
 3. Persons who act as representatives of any person in doing any of the things mentioned in this section.