Institutio Oratoria
Quintilian
Quintilian. Institutio Oratoria, Volume 1-4. Butler, Harold Edgeworth, translator. Cambridge, Mass; London: Harvard University Press, William Heinemann Ltd., 1920-1922.
Such passages may also serve as a kind of peroration after the main question. The Greeks call this παρέκβασις, the Romans egressus or egressio (digression). They may however, as I have said, be of various kinds and may deal with different themes in any portion of the speech. For instance we may extol persons or places, describe regions, record historical or even legendary occurrences.
As examples I may cite the praise of Sicily and the rape
παρέκβασις may, I think, be defined as the handling of some theme, which must however have some bearing on the case, in a passage that involves digression from the logical order of our speech. I do not see therefore why it should be assigned a special position immediately following on the statement of facts any more than I understand why they think that the name is applicable only to a digression where some statement has to be made, when there are so many different ways in which a speech may leave the direct route.