The Chiropractic Practice Act shall not be construed to include the following classes of persons:
(1) Licensed physicians and surgeons and licensed osteopathic physicians who are exclusively engaged in the practice of their respective professions;
(2) Physicians who serve in the armed forces of the United States or the United States Public Health Service or who are employed by the United States Department of Veterans Affairs or other federal agencies, if their practice is limited to that service or employment;
(3) Chiropractors licensed in another state when incidentally called into this state in consultation with a chiropractor licensed in this state; or
(4) Students enrolled in an accredited college of chiropractic when the services performed are a part of the course of study and are under the direct supervision of a licensed chiropractor.