Pollicis pressio, and Pollicis versio, were used at the combats of gladiators as signals of life or death to the vanquished combatant; or to the victor to spare or take the life of his antagonist. The pollicis pressio, by which the people granted life to the prostrate gladiator, was no more than a clenching of the fingers of both hands together, and so holding the two thumbs upright close together. The pollicis versio, which authorised the victor to kill the other as a coward, was the bending back of the thumbs. Such is Dacier's opinion; but others say the pollicis pressio was when the people held up one hand with the thumb bent, and the pollicis versio when they showed the hand with the thumb raised. Authors, however, are not perfectly agreed, though the phrases pollicem premere, and pollicem vertere, frequently occur in the Latin classics as indications of the people's will that a gladiator should live or die.

Pollio, Caius Asinius, a celebrated Latin poet and orator, was of consular dignity, and composed some tragedies which were esteemed, but are now lost. He was the first who opened at Rome a library for the use of the public. He was the friend of Mark Antony; which prevented his complying with the solicitations of Augustus, who pressed him to embrace his party. At length Augustus having wrote some verses against Pollio, he was urged to answer them: on which he said, "I shall take care of writing against a man who has the power of prescribing us." He is praised by Virgil and Horace, whose patron he was.

There was another Pollio, a friend of Augustus, who used to feed his fishes with human flesh. This cruelty was discovered when one of his servants broke a glass in the presence of Augustus, who had been invited to a feast. The master ordered the servant to be seized, but he threw himself at the feet of the emperor, and begged him to interfere, and not to suffer him to be devoured by fishes. Upon this the causes of his apprehension were examined; and Augustus, astonished at the barbarity of his favourite, caused the servant to be dismissed, all the fish ponds to be filled up, and the crystal glasses of Pollio to be broken into pieces.