Titus Livius (Livy), The History of Rome, Book 34
Cyrus Evans, Ed.

47. These were now fighting on the outside of the rampart, the fourth legion still entangled in the gate, when a new alarm arose on the opposite side of the camp. [2] The Gauls had broke in by the Quaestorian gate, and had slain the quaestor, Lucius Postumius, surnamed Tympanus, with Marcus Atinius and Publius Sempronius, praefects of the allies, [p. 1538]who made an obstinate resistance; and also, near two hundred soldiers. [3] The camp in that part had been taken, when a cohort of those who are called Extraordinaries, having been sent by the consul to defend the Quaestorian gate, killed some who had got within the rampart, drove out the rest, and opposed others who were attempting to break in. [4] About the same time, the fourth legion, and two cohorts of Extraordinaries, burst out of the gate; and thus there were three battles, in different places, round the camp; while the various kinds of shouts raised by them, called off the attention of the combatants from their own immediate conflict to the uncertain casualties which threatened their friends. The battle was maintained until mid-day with equal strength, and with nearly equal hopes. [5] At length, the fatigue and heat so far got the better of the soft relaxed bodies of the Gauls, who are incapable of enduring thirst, as to make most of them give up the fight; and the few who stood their ground, were attacked by the Romans, routed, and driven to their camp. The consul then gave the signal for retreat, on which the greater part retired; but some, eager to continue the fight, and hoping to get possession of the camp, pressed forward to the rampart, on which the Gauls, despising their small number, rushed out in a body. [6] The Romans were then routed in turn, and compelled, by their own fear and dismay, to retreat to their camp, which they had refused to do at the command of their general. [7] Thus now flight and now victory alternated on both sides. The Gauls, however, had eleven thousand killed, the Romans but five thousand. The Gauls retreated into the heart of their country, and the consul led his legions to Placentia. [8] Some writers say, that Scipio, after joining his forces to those of his colleague, overran and plundered the country of the Boians and Ligurians, as far as the woods and marshes suffered him to proceed; others, that, without having effected any thing material, he returned to Rome to hold the elections.