Institutio Oratoria

For example, this made it necessary for Cicero to digress even in the exordium when he was defending Milo, as is clear from the short speech [*]( The speech actually delivered, not the long speech which has come down to us, but was never delivered. ) which he made on that occasion. But the orator who makes some preface to the main question or proposes to follow up his proofs with a passage designed to commend them to the jury, may digress at some length. On the other hand, if he breaks as say in the middle of his speech, he should not be long in returning to the point from which he departed.