Section 60. Sections fifty-four to fifty-nine, inclusive shall not prohibit advice or service, in a case of emergency, by a person other than a registered veterinarian, nor shall they prohibit farmers from rendering services to their neighbors, if they do not hold themselves out as registered veterinarians, nor shall they be held to discriminate against any particular school or system of veterinary medicine. They shall not apply to a commissioned veterinarian of the United States army in the performance of his official duty; nor to a veterinarian from another state who is a legal practitioner in that state, when in actual consultation with a legal practitioner of this commonwealth; nor to any registered pharmacist prescribing gratuitously, if he does not violate section fifty-nine.