Section 32. Tuberculin as a diagnostic agent for the detection of tuberculosis in domestic animals shall be used only upon cattle brought into the commonwealth and upon cattle in quarantine stations; but it may be used as such diagnostic agent on any animal in any other part of the commonwealth, with the written consent of the owner or person in possession thereof, and upon animals which have been reported as tuberculous upon physical examination by a competent veterinary surgeon, and also as provided in section thirty-three B. Such tests by the use of tuberculin shall be made without charge to citizens of the commonwealth, and in all other cases the expense of such tests shall be paid by the owner of such animals or by the person in possession thereof.