Whatever may be the true explanation of surrender in connection with contracts, for the present purpose we need not go further than the common case of noxoe deditio for wrongs. Neither is the seeming adhesion of liability to the very body which did the harm of the first importance. [15] The Roman law dealt mainly with living creatures,--with animals and slaves. If a man was run over, it did not surrender the wagon which crushed him, but the ox which drew the wagon. /1/ At this stage the notion is easy to understand. The desire for vengeance may be felt as strongly against a slave as against a freeman, and it is not without example nowadays that a like passion should be felt against an animal. The surrender of the slave or beast empowered the injured party to do his will upon them. Payment by the owner was merely a privilege in case he wanted to buy the vengeance off. It will readily be imagined that such a system as has been described could not last when civilization had advanced to any considerable height. What had been the privilege of buying off vengeance by agreement, of paying the damage instead of surrendering the body of the offender, no doubt became a general custom. The Aquilian law, passed about a couple of centuries later than the date of the Twelve Tables, enlarged the sphere of compensation for bodily injuries. Interpretation enlarged the Aquilian law. Masters became personally liable for certain wrongs committed by their slaves with their knowledge, where previously they were only bound to surrender the slave. /2/ If a pack-mule threw off his burden upon a passer-by because he had been improperly overloaded, or a dog which might have been restrained escaped from his master and bit any one, the old noxal action, as it was called, gave way to an action under the new law to enforce a general personal liability. /3/ Still later, ship-owners and innkeepers were made liable [16] as if they were wrong-doers for wrongs committed by those in their employ on board ship or in the tavern, although of course committed without their knowledge. The true reason for this exceptional responsibility was the exceptional confidence which was necessarily reposed in carriers and innkeepers. /1/ But some of the jurists, who regarded the surrender of children and slaves as a privilege intended to limit liability, explained this new liability on the ground that the innkeeper or ship-owner was to a certain degree guilty of negligence in having employed the services of bad men? This was the first instance of a master being made unconditionally liable for the wrongs of his servant. The reason given for it was of general application, and the principle expanded to the scope of the reason.