Institutio Oratoria
Quintilian
Quintilian. Institutio Oratoria, Volume 1-4. Butler, Harold Edgeworth, translator. Cambridge, Mass; London: Harvard University Press, William Heinemann Ltd., 1920-1922.
It is not, however, necessary to go back further than three feet, and only that if the feet contain less than three syllables, for we must avoid the exactitude of verse: on the other hand, we must not go back less than two: otherwise we shall be dealing with a foot and not with rhythm. But in this connexion the dichoreus may be regarded as one foot, if indeed a foot consisting of two chorei can be considered as a single foot.
The same is true of the paean composed of the choreus and a pyrrhic, a foot which is regarded as specially suitable to the beginning of a sentence, or of the other paean, formed of three shorts followed by a long, to which the conclusion is specially dedicated. It is of these two forms that writers on rhythm generally speak. Some, however, call all feet containing three short syllables and a long by the name of paean, irrespective of the position of the long syllable, and merely taking into account the total number of time-lengths that it contains.
The dochmiac, again, which consists of a bacchius and an iambus, or of an iambus and a cretic, forms a solid and severe conclusion. The spondee, so frequently employed in this position by Demosthenes, is used with varying effect. It is most impressive when preceded by a cretic, as in the following instance: De qua ego nihil dicam, nisi depellendi criminis causa. [*](pro Cael. xiii. 31. Concerning which I will say nothing except for the purpose of refuting the charge. ) Again there is a point, of the importance of which I spoke above, namely that it makes a considerable difference whether two feet are contained in a single word
For the mere fact that words are separated from each other involves an imperceptible length of time: for instance, the spondee forming the middle foot of a pentameter must consist of the last syllable of one word and the first of another, otherwise the verse is no verse at all. It is permissible, though less satisfactory, for the spondee to be preceded by an anapaest: e.g. muliere non solum nobili, verum etiami nota. [*](pro Cael. xiii. 31. A woman, not only of noble birth, but even notorious. )