" If, however, though there has been in this'case a technical legal conversion, the real and substantial claim of the plaintiff is merely to recover damages for the breach of an illegal contract; if he must, notwithstanding the form of his action, claim in fact by and through his contract, he cannot evade the consequences of his illegal act by adopting a fictitious action, allowed in ordinary cases for the purposes of the remedy. In some cases the plaintiff, for convenience of his remedy, when his claim arises under a contract, is allowed to allege his gravamen in a criminal neglect of duty in the manner of performing, or in neglecting to perform, the contract. Govett v. Radnidge, 3 East, 62. But in such case, by varying the form of the remedy, the plaintiff cannot deprive his adversary of any defence, such as infancy, which he might have set up, if the claim had been made for a breach of the contract. Jennings v. Rundall, 8 T. R. 335; Green v. Green-bank, 2 Marshall, 485; Fitts v. Hall, 9 N. H. 441.
"The question, then, becomes material whether the only real injury which the plaintiff suffered was by a breach of the contract; or whether the driving of the horse to another place was a substantial invasion of the plaintiff's right of property.
"When the defendant voluntarily drove the horse beyond the limits for which he was hired, he acted wholly without right. He then took the horse into his own control, without any authority or license from the owner. The conversion was in law as complete, the wrongful invasion of the plaintiff's right of property was as absolute as if, instead of driving the horse a few miles beyond the place for which he had hired him, he had detained and used him for a year, or any other indefinite time, or had driven him to market and sold him. If taking the wrongful control of the horse, and driving him ten miles, was not a substantial conversion, how far must the defendant have driven him ? how long must he have detained him ? and what other and further wrongful acts was it necessary that he should do, in order to make himself a substantial and real wrong-doer ? It would seem to be quite clear that if the original act, assuming control over the horse, was not a substantial invasion of the plaintiff's right of property, no subsequent use or abuse of the horse by the defendant could make it so; and that if the defendant cannot on the facts of this case be charged for the conversion of the horse, he could not have been if he had sold or wilfully destroyed him. In other words, the plaintiff having delivered the horse into the defendant's hands on a contract that was illegal, but which nevertheless left the general property in the plaintiff, the defendant may do what he will with the horse, and the plaintiff can have no remedy, because whatever he does can be no was a wrongful invasion of the plaintiff's right of property, having nothing to do with the contract, and that if the mere more than a breach of his unlawful contract to return the horse. This does not appear to be a reasonable conclusion. The cases are not entirely unanimous as to what acts of a bailee, who receives goods on a void or voidable contract, are sufficient to make him liable for a tortious conversion. The question has arisen most frequently where infancy has been set up as a defence. Vasse v. Smith, 6 Cranch, 231; Campbell v. Stakes, 2 Wend. 137; Mills v. Graham, 4 Bos. & Pul. 140; Homer v. Thwing, 3 Pick. 492, are strong authorities to the point that an infant who receives goods on a contract, and disposes of the property without right, is liable in trover; and these cases are cited and approved by the learned Chief Justice in Fitts v. Hall, 9 N. H. 443. Wilt v. Welsh, 6 Watts, 9, and perhaps Jennings v. Rundall, 8 T. R. 336, must be regarded as somewhat in conflict with these cases. Jennings v. Rundall, however, is criticised and doubted in Fitts v. Hall. Homer v. Thwing, 3 Pick. 492, maintains the position that in a case like this, driving the horse beyond the place for which he was hired, is a substantial conversion and a direct injury to the plaintiff's right of property, and not in substance a mere breach of the defendant's contract. In that case it was held that infancy was no defence to trover for such a conversion of a horse. If the action had been substantially upon the infant's voidable contract, he could not have been charged. We think the weight of authority and of argument are very decidedly in favor of the rule declared in Homer v. Thwing.
"From these premises the conclusion would seem to follow that trover may be maintained on the facts of this case. If the plaintiff made an illegal contract respecting the horse, that contract is void; but the illegal contract being for a temporary use of the horse, the consequences do not extend to a forfeiture of the plaintiff's general right of property; and for a wrongful invasion of that right he may maintain trover against the defendant, the bailee, or a third person. This is the doctrine of Dwight v. Brewster, 1 Pick. 51. In that case the contract was not only void but illegal.
"Driving the horse beyond the place for which he was hired is a wrongful invasion of the plaintiff's right of property, and a substantial conversion. In trover for such a conversion, the plaintiff's claim is neither in form nor in substance by, through, or under the illegal contract, and the invalidity and illegality of the contract are no defence to the suit. The contract is no link in the chain of the plaintiff's case; he shows the contract, which was invalid and illegal; but notwithstanding the contract, and in spite of it, his right of property remained. That right has been directly invaded by the defendant's wrongful act, and this action is the appropriate remedy. . . .
"One case of high authority we are obliged to regard as in conflict with the conclusion to which we have arrived, and that is the recent case of Gregg v. Wyman, 4 Cush. 322, in the Supreme Court of Massachusetts. The able and elaborate judgment in that case, and the great respect due to all the fact that the plaintiff must show possession to have been obtained through an illegal contract, was sufficient to prevent him decisions of that court, have caused the principal hesitation which we have felt in holding that the present action could be maintained.