Courts are often heard to say, as does the Wisconsin court in a recent case, that an action of replevin may be defeated by proof of title paramount in a third person, even though the plaintiff has shown a right to possession as against the defendant sufficient to support an action of trespass. This seems so anomalous, so opposed to our notion of other possessory actions, for example, trespass, and even trover, where the plaintiff need show only a better right to possession to recover, that we are led to wonder how such a doctrine ever obtained a foothold in replevin. However, it has long been asserted as rule of the common law; and it should be observed at the outset that the availability of this defense is not affected by the procedural codes adopted in many states. For the codes have been interpreted to work no change in substantive rights, and this is considered a substantive defense to any action in which the specific restitution of personal property is demanded. The origin of this unusual doctrine is worth considering in an effort to determine its present value as a rule of law and its effect on the modern cases.