Institutio Oratoria

A colon, on the other hand, is the expression of a thought which is rhythmically complete, but is meaningless if detached from the whole body of the sentence. For example O callidos homines [*]( From the lost pro Cornelio. O the cunning of those men! O what careful forethought! I ask you did one of us fail to note that such would be your action? ) is complete in itself, but is useless if removed from the rest of the sentence, as the hand, foot or head if separated from the body. He goes on, O rein excogitatam. At what point do the members begin to form a body? Only when the conclusion is added: quem, quaeso, nostrum fefellit, id vos ita esse facturos? a sentence which Cicero regards as unusually concise. Thus as a rule commata and cola are fragmentary and require a conclusion.

The period is given a number of different names by Cicero, [*]( Orat. lxi. 204. ) who calls it ambitus, circuitus, comprehensio, continuatio and circumscriptio. It has two forms. The one is simple, and consists of one thought expressed in a number of words, duly rounded to a close. The other consists of commata and cola, comprising a number of different thoughts: for example, aderat ianitor carceris, carnriex praetoris [*](Verr. v. xlv. 118. There stood the jailer, the praetor's executioner. ) and the rest.