“In civil cases the medical witness should, previous to the trial, make an agreement with the solicitor who has called him with reference to the fee he is to receive. Before consenting to appear as a witness the practitioner should insist on having all the facts of the case put before him in writing. In this way only can he decide as to whether in his opinion the plaintiff or defendant is right as regards the medical evidence. If summoned by the side on which he thinks the medical testimony is correct, then it is his duty to consent to appear. If, however, he is of opinion that the medical evidence is clearly and correctly on the opposite side, then he ought to refuse to appear and give evidence; and, indeed, the lawyer would not desire his presence in the witness-box unless he could uphold the case.”