6. Nothing in this Act shall apply to- (a) any medical treatise or book, or any treatise or book dealing with the subject from a bona fide scientific or social standpoint, or (b) any advertisement, or any article or thing sent confidentially in the prescribed manner only to a medical practitioner or to a wholesale or retail chemist for the purpose of his business, or (c) any advertisement made, printed or published with the previous sanction of such person or persons as the Government may appoint in this behalf. Explanation.- “Medical practitioner” in this section includes a person regularly practising either the allopathic, homeopathic, Ayurvedic, Unani or any other system of medicine.