Readers of Persius have always recognized that he owed a special debt to Horace. In the appendix to his edition of 1605 Casaubon noted most of the important allusions, and later editors like Conington and Villeneuve made excellent use of this material when commenting on individual points. In recent times attention has come to focus more upon the way in which the allusions are made. In the first section of his Berlin dissertation (1940) Kugler showed how in a number of cases Persius gave a literal meaning to a Horatian metaphor. Then in Philologus 1955 Henss distinguished ten ways in which Persius varied his Horatian material – e.g. by altering plural to singular, putting species for genus, and switching from active to passive voice. Here is an example of his procedure:

This is an illustration of what Henss calls Auflösung der Prägnanz – making implications explicit. Henss' paper, which is admirably perceptive and lucid, is concerned above all with classification.