On the 13th of October, 1131, the king was riding with his son on the hillock of Saint-Gervais (to-day the site of the Mairie of the IVth Arrondissement, on the Rue de Rivoli, a little beyond the Hôtel de Ville), when a wandering pig ran between the legs of the young man's horse, causing him to bolt and throw his rider, who was so badly injured that he died in a few hours. This led to the promulgation of a royal ordinance forbidding the proprietors of swine in the city to allow them to run at large, under penalty of confiscation for the benefit of the executioner of Paris. This regulation was several times renewed,--in 1261 under Saint Louis, in 1331 under Philippe VI, and in 1369 under Charles V, and extended to the faubourgs of Paris and the surrounding districts. The decree of 1331 gave the sergeants of the city authority to kill all those which they found wandering at liberty, to keep the head for themselves provided they transported the body to the Hôtel-Dieu. The pigs of the abbey of Saint-Antoine alone were exempted from this regulation, and, that they might be recognized, they bore a bell marked with a cross. Louis le Gros, already occupied with measures to repress the growing power of the great nobles, commenced the fortifications of Paris, which were not completed until during the reign of his son, with a view of guarding his capital against any sudden attack. It is recorded that he adopted the habit of the great Caliph of the _Arabian Nights_, of traversing the streets at night in disguise and mingling familiarly with the people,--but with the design of drawing from them their complaints against their feudal lords and their knowledge of their machinations. They were not without their grievances against the king himself, and it was not till the reign of his son that was abolished the right of the royal officers, when the king came to Paris, to enter the houses of the bourgeoisie and carry off for their own use the bedding and the downy pillows they found therein.