Thé defendants had an oral contract with the Boston and Maine Railroad to carry the mail between the rail*152road station and the post office in Amesbury, and when the train arrived at seventeen minutes after nine on the morning of the accident, their employee was at the station with an ordinary express or delivery wagon. As somewhat vaguely described in the exceptions, “the seat had . . . two irons down each side and . . . two iron straps hitched on the inside of the wagon so that it would keep the seat from slipping on the body of the wagon.” The plaintiff was a railway mail clerk in the employ of the United States government; and there was evidence that by the rules of the post office department he was required to keep the mail that was carried on this particular train in his personal custody until it was delivered at the post office. The driver was to return to the station with mail for the train that would leave Amesbury at thirty-three minutes after nine; and both the plaintiff and the driver testified that this work necessarily was done in a hurried manner, and that it was usual for the driver “to grab the mail and jerk it on to the wagon, . . . grab the reins and start off . . . pell-mell up the street.”
On the day of the accident, after the mail was placed in the wagon, the plaintiff sat upon the seat, the driver unhitched the weight from the horse, took the reins and got wholly or partly on the wagon. The horse then suddenly started and the plaintiff and the seat went backward, the plaintiff falling on his back in the body of the wagon. An examination after the accident revealed fresh, clean breaks in two of the small iron straps that held the seat, admittedly due to the accident.
The plaintiff seeks to hold the defendants responsible for his injury solely on the ground that they negligently furnished an unsafe, improper and insecure wagon to carry him.. The allegation that the horse was unbroken and vicious has been waived; and neither in the pleadings nor in the brief is any complaint made with reference to the conduct of the driver. The brief reference to the contract in the exceptions discloses no obligation on the part of the defendants to convey the plaintiff, unless it be implied from their agreement “to carry the mail” to the post office. They were not common carriers, and upon the evidence they owed the plaintiff at most no higher duty with regard to the wagon than that of exercising reasonable care to provide one that was safe. It is not contended by the plaintiff that the wagon was in fact *153unsafe or improper except as to the irons that held the seat and which broke when the strain of a sudden start was put upon them. But the fastening was one in common use and suitable for the purpose that it served. It does not appear that the most careful inspection would have disclosed any defect or weakness in it. The plaintiff cannot invoke the doctrine of res ipsa loquitur to supply a presumption of culpability, for not only does he fail to exclude the operation of causes other than the negligence of the defendants, but the most probable inference to be drawn from the facts is that when the horse started the plaintiff fell backward and pulled the seat with him, — and indeed the driver so testified. The evidence would not warrant the jury in finding that the accident was caused by negligence on the part of the defendants. Childs v. American Express Co. 197 Mass. 337. Trim v. Fore River Ship Building Co. 211 Mass. 593.
Exceptions overruled.