Here is a good excerpt leading up to a short explanation of exempli gratia, in the scrolls of Philodemus, from Stanford Encyclopedia of Philosophy, which brings up more questions, regarding what is thought to be actually written by Philodemus (perhaps this is addressed somewhere else in the forum).
2.2.3 Early Publications and Modern Reading of the Papyri
These delays conspired with what many observers at the time considered the uninspiring nature of the works preserved in the papyri to dampen wider interest in and notice of them, despite their unique status. This state-of-affairs persisted until the unification of Italy (1861), when a new series of publications of facsimiles of the papyrus texts, engravings of drawings (Italian: disegni) made soon after the rolls were opened, appeared in quick succession (see the Bibliographical Note, infra). Now the texts of Philodemus finally became objects of sustained study by scholars interested in Epicureanism.
Nonetheless, numerous editions of Philodemus’ works, especially early ones, are unreliable. Many were not based on a reading of the papyri themselves, but rather on the disegni, which are frequently wrong, and this led editors to be bolder about changing the texts presented in these copies, filling in gaps, and interpreting the results than they might have been had they read the papyri instead. In many such cases, better reading of the papyrus has shown that the text ran very differently indeed from the conjectures that have commonly served as the basis of reconstructions of the views of Philodemus and others. One common problem has been the mistaking of what turns out to be a citation of an opponent for something Philodemus himself maintains (and vice versa).
There are other serious obstacles to understanding, especially the condition of the papyri themselves. The books were written on sheets of papyrus pasted together into lengths of, say, 8–16 meters, which were rolled up from right to left and therefore read from left to right, beginning to end. The texts are arranged in parallel columns, at times well over 200 of them, of 20–45 lines, each consisting of 16–40 letters; the numbers of lines and letters are fairly uniform in each roll.
There are holes (‘lacunae’) of varying size; surfaces may have been badly abraded in the process of unrolling; ink may have faded, or even vanished altogether; glues used to hold the papyri together and mount them have in some cases penetrated and darkened them. Significant advances in reading the papyri have been made, however, especially by the use of microscopes (first in 1970, then, from 1995, with built-in illumination) and, from 2000, of digital photographs taken mostly in the near-infrared region (‘multi-spectral images’). The problems of continuity posed by the way in which the papyri were opened and read have also recently been addressed in a systematic way. Guglielmo Cavallo’s study (1983) of the scribal hands used in the papyri allowed the texts to be grouped and dated, and it allowed the recognition that numerous pieces had once belonged to the same roll. These technical and philological advances, which have dramatically improved and extended our access to Philodemus’ thought, now require the re-edition of all texts of Herculaneum papyri. There are also newer technical methods which may soon change the situation again by providing three-dimensional images of opened papyri or even reading still rolled-up pieces without opening them.
2.2.4 Reconstructing Philodemus’ philosophical oeuvre
In many texts we have lost the pages placed at the end of a roll, on which a scribe would write the work’s author and title (and sometimes more information too, such as the number of columns or standard lines the bookroll contained); nearly all the title-pages from the beginnings of the rolls have been lost, as well. Many such orphaned rolls have been assigned to Philodemus indirectly, on the basis of the nature of the bookroll and of the hand in which it was copied, and of the work’s style and content. Scholars have also given titles to some works based on their content and, in some cases, relying on references to such titles in other works of Philodemus’. A related difficulty is posed by the possibility that titles may have taken various forms, as in the papyri of On Vices, where the title-pages at the beginning of the rolls seem to have had a somewhat fuller title, those at the ends of the rolls a shorter version. The point is relevant because Philodemus’ philosophical production can of course be rightly described and evaluated only on the basis of an accurate list of his writings. Most attributions of works to Philodemus are generally accepted by scholars; conjectured titles, however, should often be understood as exempli gratia.